# On the Performance of a Photonic Reconfigurable Electromagnetic Band Gap Antenna Array for 5G Applications

Taha A Elwi, Fatma Taher, Bal S Virdee, Mohammad Alibakhshikenari, Ignacio J Garcia Zuazola, Astrit Krasniqi, Amna Shibib Kamel, Nurhan Türker Tokan, Salahuddin Khan, Naser Ojaroudi Parchin, et al.

<figure><img src="image_1.png" /></figure>

## ► To cite this version:

Taha A Elwi, Fatma Taher, Bal S Virdee, Mohammad Alibakhshikenari, Ignacio J Garcia Zuazola, et al.. On the Performance of a Photonic Reconfigurable Electromagnetic Band Gap Antenna Array for 5G Applications. IEEE Access, 2024, 12, pp.60849 - 60862. 10.1109/access.2024.3392368. hal-04569351

HAL Id: hal-04569351

https://hal.science/hal-04569351

Submitted on 6 May 2024

HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.

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<figure><img src="image_2.png" /></figure>
# On the Performance of a Photonic Reconfigurable Electromagnetic Band Gap Antenna Array for 5G Applications

Taha A Elwi, Fatma Taher, Bal S Virdee, Mohammad Alibakhshikenari, Ignacio J Garcia Zuazola, Astrit Krasniqi, Amna Shibib Kamel, Nurhan Türker Tokan, Salahuddin Khan, Naser Ojaroudi Parchin, et al.

<figure><img src="image_1.png" /></figure>

## ► To cite this version:

Taha A Elwi, Fatma Taher, Bal S Virdee, Mohammad Alibakhshikenari, Ignacio J Garcia Zuazola, et al.. On the Performance of a Photonic Reconfigurable Electromagnetic Band Gap Antenna Array for 5G Applications. IEEE Access, 2024, 12, pp.60849 - 60862. 10.1109/access.2024.3392368. hal-04569351

HAL Id: hal-04569351

https://hal.science/hal-04569351v1

Submitted on 6 May 2024

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_2.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
Received 25 March 2024, accepted 17 April 2024, date of publication 22 April 2024, date of current version 6 May 2024.

Digital Object Identifier 10.1109/ACCESS.2024.3392368

RESEARCH ARTICLE

# On the Performance of a Photonic Reconfigurable Electromagnetic Band Gap Antenna Array for 5G Applications

TAHA A. ELWI<sup>1,2</sup>, FATMA TAHER<sup>1,3</sup>, (Senior Member, IEEE),

BAL S. VIRDEE<sup>1,4</sup>, (Senior Member, IEEE),

MOHAMMAD ALIBAKHSHIKENARI<sup>1,5</sup>, (Member, IEEE), IGNACIO J. GARCIA ZUAZOLA<sup>1,4</sup>,

ASTRIT KRASNIQI<sup>1,4</sup>, AMNA SHIBIB KAMEL<sup>1</sup>, NURHAN TÜRKER TOKAN<sup>1,6</sup>,

SALAHUDDIN KHAN<sup>7</sup>, NASER OJAROUDI PARCHIN<sup>1,8</sup>, (Senior Member, IEEE),

PATRIZIA LIVRERI<sup>1,9</sup>, (Senior Member, IEEE), IYAD DAYOUB<sup>1,10,11</sup>, (Senior Member, IEEE),

GIOVANNI PAU<sup>1,12</sup>, (Senior Member, IEEE), SONIA AÏSSA<sup>1,13</sup>, (Fellow, IEEE),

ERNESTO LIMITI<sup>1,14</sup>, (Senior Member, IEEE), AND

MOHAMED FATHY ABO SREE<sup>1,15</sup>

Corresponding authors: Taha A. Elwi (taelwi82@gmail.com), Mohammad Alibakhshikenari (mohammad.alibakhshikenari@uc3m.es), and Giovanni Pau (giovanni.pau@unikore.it)

Dr. Mohammad Alibakhshikenari acknowledges support from the CONEX (CONnecting EXcellence)-Plus programme funded by Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 801538. The authors also sincerely appreciate funding from Researchers Supporting Project number (RSP2024R58), King Saud University, Riyadh, Saudi Arabia.

**ABSTRACT** In this paper, a reconfigurable Multiple-Input Multiple-Output (MIMO) antenna array is presented for 5G portable devices. The proposed array consists of four radiating elements and an Electromagnetic Band Gap (EBG) structure. Planar monopole radiating elements are employed in the array with Coplanar Waveguide Ports (CWPs). Each CWP is grounded on one side to a reflecting L-shaped structure that has an effect of improving the antenna's directivity. It is shown that by inductively connecting Minkowski fractal structure of 1st order to the radiating element, the impedance matching is improved that results in enhancement in the array's bandwidth performance. The EBG structure is used to provide the isolation between antenna elements in the MIMO array. The fractal structure is connected to the L-shaped reflector through four photosensitive light dependent resistor (LDR) switches. The effect of various LDR switching configurations on the performance of the antenna is investigated. The proposed array provides a novel performance in terms of S-parameters with enhancements in the radiation properties. Such enhancements

The associate editor coordinating the review of this manuscript and approving it for publication was Derek Abbott.

<footnote n="1">¹International Applied and Theoretical Research Center (IATRC), Baghdad 10001, Iraq</footnote>

<footnote n="2">²Islamic University Centre for Scientific Research, The Islamic University, Najaf 100986, Iraq</footnote>

<footnote n="3">³College of Technological Innovation, Zayed University, Dubai, United Arab Emirates</footnote>

<footnote n="4">⁴Center for Communications Technology, London Metropolitan University, N7 8DB London, U.K.</footnote>

<footnote n="5">⁵Department of Signal Theory and Communications, Universidad Carlos III de Madrid, Leganés, 28911 Madrid, Spain</footnote>

<footnote n="6">⁶Department of Electronics and Communications Engineering, Yildiz Technical University, Esenler, 34220 Istanbul, Turkey</footnote>

<footnote n="7">⁷College of Engineering, King Saud University, Riyadh 11421, Saudi Arabia</footnote>

<footnote n="8">⁸School of Computing Engineering and the Built Environment, Edinburgh Napier University, EH10 5DT Edinburgh, U.K.</footnote>

<footnote n="9">⁹Department of Engineering, University of Palermo, Palermo, 90128 Sicily, Italy</footnote>

<footnote n="10">¹⁰Institut d'Électronique de Microélectronique et de Nanotechnologie (IEMN), CNRS UMR 8520, ISEN, Centrale Lille, Université Polytechnique Hauts-de-France, University of Lille, 59313 Valenciennes, France</footnote>

<footnote n="11">¹¹INSA Hauts-de-France, 59313 Valenciennes, France</footnote>

<footnote n="12">¹²Faculty of Engineering and Architecture, Kore University of Enna, 94100 Enna, Italy</footnote>

<footnote n="13">¹³Institut National de la Recherche Scientifique (INRS), Université du Quebec, Montreal, QC H5A 1K6, Canada</footnote>

<footnote n="14">¹⁴Department of Electronic Engineering, University of Rome “Tor Vergata,” 00133 Rome, Italy</footnote>

<footnote n="15">¹⁵Department of Electronics and Communications Engineering, Arab Academy for Science, Technology and Maritime Transport, Cairo 11865, Egypt</footnote>
Received 25 March 2024, accepted 17 April 2024, date of publication 22 April 2024, date of current version 6 May 2024.

Digital Object Identifier 10.1109/ACCESS.2024.3392368

RESEARCH ARTICLE

# On the Performance of a Photonic Reconfigurable Electromagnetic Band Gap Antenna Array for 5G Applications

TAHA A. ELWI<sup>1,2</sup>, FATMA TAHER<sup>1,3</sup>, (Senior Member, IEEE),

BAL S. VIRDEE<sup>1,4</sup>, (Senior Member, IEEE),

MOHAMMAD ALIBAKHSHIKENARI<sup>1,5</sup>, (Member, IEEE), IGNACIO J. GARCIA ZUAZOLA<sup>1,4</sup>,

ASTRIT KRASNIQI<sup>1,4</sup>, AMNA SHIBIB KAMEL<sup>1</sup>, NURHAN TÜRKER TOKAN<sup>1,6</sup>,

SALAHUDDIN KHAN<sup>7</sup>, NASER OJAROUDI PARCHIN<sup>1,8</sup>, (Senior Member, IEEE),

PATRIZIA LIVRERI<sup>1,9</sup>, (Senior Member, IEEE), IYAD DAYOUB<sup>1,10,11</sup>, (Senior Member, IEEE),

GIOVANNI PAU<sup>1,12</sup>, (Senior Member, IEEE), SONIA AÏSSA<sup>1,13</sup>, (Fellow, IEEE),

ERNESTO LIMITI<sup>1,14</sup>, (Senior Member, IEEE), AND

MOHAMED FATHY ABO SREE<sup>1,15</sup>

Corresponding authors: Taha A. Elwi (taelwi82@gmail.com), Mohammad Alibakhshikenari (mohammad.alibakhshikenari@uc3m.es), and Giovanni Pau (giovanni.pau@unikore.it)

Dr. Mohammad Alibakhshikenari acknowledges support from the CONEX (CONnecting EXcellence)-Plus programme funded by Universidad Carlos III de Madrid and the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 801538. The authors also sincerely appreciate funding from Researchers Supporting Project number (RSP2024R58), King Saud University, Riyadh, Saudi Arabia.

**ABSTRACT** In this paper, a reconfigurable Multiple-Input Multiple-Output (MIMO) antenna array is presented for 5G portable devices. The proposed array consists of four radiating elements and an Electromagnetic Band Gap (EBG) structure. Planar monopole radiating elements are employed in the array with Coplanar Waveguide Ports (CWPs). Each CWP is grounded on one side to a reflecting L-shaped structure that has an effect of improving the antenna's directivity. It is shown that by inductively connecting Minkowski fractal structure of 1st order to the radiating element, the impedance matching is improved that results in enhancement in the array's bandwidth performance. The EBG structure is used to provide the isolation between antenna elements in the MIMO array. The fractal structure is connected to the L-shaped reflector through four photosensitive light dependent resistor (LDR) switches. The effect of various LDR switching configurations on the performance of the antenna is investigated. The proposed array provides a novel performance in terms of S-parameters with enhancements in the radiation properties. Such enhancements

The associate editor coordinating the review of this manuscript and approving it for publication was Derek Abbott.

<footnote n="1">¹International Applied and Theoretical Research Center (IATRC), Baghdad 10001, Iraq</footnote>

<footnote n="2">²Islamic University Centre for Scientific Research, The Islamic University, Najaf 100986, Iraq</footnote>

<footnote n="3">³College of Technological Innovation, Zayed University, Dubai, United Arab Emirates</footnote>

<footnote n="4">⁴Center for Communications Technology, London Metropolitan University, N7 8DB London, U.K.</footnote>

<footnote n="5">⁵Department of Signal Theory and Communications, Universidad Carlos III de Madrid, Leganés, 28911 Madrid, Spain</footnote>

<footnote n="6">⁶Department of Electronics and Communications Engineering, Yildiz Technical University, Esenler, 34220 Istanbul, Turkey</footnote>

<footnote n="7">⁷College of Engineering, King Saud University, Riyadh 11421, Saudi Arabia</footnote>

<footnote n="8">⁸School of Computing Engineering and the Built Environment, Edinburgh Napier University, EH10 5DT Edinburgh, U.K.</footnote>

<footnote n="9">⁹Department of Engineering, University of Palermo, Palermo, 90128 Sicily, Italy</footnote>

<footnote n="10">¹⁰Institut d'Électronique de Microélectronique et de Nanotechnologie (IEMN), CNRS UMR 8520, ISEN, Centrale Lille, Université Polytechnique Hauts-de-France, University of Lille, 59313 Valenciennes, France</footnote>

<footnote n="11">¹¹INSA Hauts-de-France, 59313 Valenciennes, France</footnote>

<footnote n="12">¹²Faculty of Engineering and Architecture, Kore University of Enna, 94100 Enna, Italy</footnote>

<footnote n="13">¹³Institut National de la Recherche Scientifique (INRS), Université du Quebec, Montreal, QC H5A 1K6, Canada</footnote>

<footnote n="14">¹⁴Department of Electronic Engineering, University of Rome “Tor Vergata,” 00133 Rome, Italy</footnote>

<footnote n="15">¹⁵Department of Electronics and Communications Engineering, Arab Academy for Science, Technology and Maritime Transport, Cairo 11865, Egypt</footnote>
are achieved with low separation gaps between antenna elements (about $\lambda_o$/16 at 3.5 GHz). It is shown that the array's operational bands centered at 3.5 GHz and 4.65 GHz can be selected by activating certain LDR switches. The electromagnetic exposure of the array on the human body is investigated by determining the specific absorption rate (SAR). It is found that the proposed antenna shows lower SAR values compared to other antennas reported in literature. With the proposed EBG structure, the gain of the array is increased 7.5 dB (from -3.5 dBi to +4 dBi) at 3.5 GHz and by 14.3 dB (from -8.7 dBi to +5.6 dBi) at 4.65 GHz. The average radiation efficiency between 3.5 GHz and 5.5 GHz increased by 42% from 20% to 62%. Excellent radiation characteristics of the EBG array makes it suitable for 5G portable devices such as tablets.

**INDEX TERMS** Electromagnetic Band Gap (EBG), multiple-input multiple-output (MIMO), 5G system, antenna arrays, specific absorption rate (SAR), photosensitive light dependent resistor (LDR).

# I. INTRODUCTION

Over the last decade, wireless communication technology has undergone rapid advancements, leading to increased demand for higher channel capacity and lower bit error rates [1]. Multiple-Input Multiple-Output (MIMO) is a crucial technology that has significantly contributed to address these demands [2]. These developments have improved various aspects of wireless communications including signal quality, enhanced throughputs, quality of service (QoS), minimizing fading effects, reduced latency, improved coverage, and energy efficiency [3], [4]. The reconfiguration mechanism applied to the MIMO antenna permits wireless systems to dynamically adjust and adapt to different communication scenarios, frequencies, or conditions [5]. This flexibility offers several benefits and advantages in terms of frequency agility, spectrum efficiency, interference mitigation, and adaptive beamforming [6]. It should be noted that the surrounding environment of a MIMO antenna system plays a crucial role in determining its gain characteristics, particularly in the context of reconfigurable antennas [7].

Coplanar waveguide (CPW) antennas have the advantages of easy fabrication, low cost, compact size, and multiband operation [8]. Synthetic metamaterial surfaces such as soft and hard surface defects, frequency selective surfaces, artificial magnetic conductors, and Electromagnetic Band Gap (EBG) structures have been widely used to replace traditional conductors in most microwave structures [9]. These technologies are widely used for suppressing surface waves between antenna elements [10].

EBG structures are engineered periodic arrays of dielectrics or metals that exhibit photonic band gap ranges where electromagnetic waves are prohibited from propagating through the material. These structures are designed to control the behavior of electromagnetic waves by creating stopbands in the frequency spectrum [11], [12]. EBG structures have been utilized for a variety of applications. Enhancing antenna gain and bandwidth are among the significant benefits they offer [13].

In 5G networks, 3GPP classifies the two main communication bands as FR1 (below 7.125 GHz) and FR2 (above 24.25 GHz) [14]. The use of millimeter-wave (mmW) spectrum results in significant reduction of antenna size because of the shorter wavelength and increase in bandwidth [15].

However, the propagation of mmW through buildings becomes extremely difficult since the skin depth and attenuation increase with increasing frequency [16], [17]. Sub-6 GHz frequencies remain crucial for achieving reliable coverage, while higher-frequency millimeter waves offer high-capacity solutions for open areas [18], [19].

In this paper, a reconfigurable MIMO antenna array with LDR switches is designed for 5G Applications. Isolation between the radiating elements of the MIMO array is enhanced by embedding EBG strips. The radiating elements consist of a monopole that is fed through a CPW structure, and the RF energy is launched through a matching load circuit and L-shaped reflector. By controlling the operation of LDR switches on the antenna, the proposed MIMO array provides reconfigurability and excellent radiation patterns.

# II. ANTENNA ARRAY STRUCTURE

The proposed MIMO antenna array, which is shown in Fig. 1, is designed to operate at sub-6GHz frequencies. Each antenna element consists of a monopole fed by a CPW port. The antenna ground-plane, which is an L-shaped reflector, is used to direct the radiation in a specific direction. An impedance matching structure, which is constructed from the first order Minkowski fractal, is inductively coupled to the radiating element to improve the array's bandwidth performance. The matching structure is attached to the L-shaped reflecting structure via four LDR switches that control the antenna surface current distribution and thereby its reconfigurability. All antenna elements were fabricated on an FR4 substrate having dielectric constant ($\epsilon_r$) of 4.3 and loss-tangent ($\tan\delta$) of 0.025.

The physical size of the array is 64×64 × 1.6 mm³ which is suitable for tablets and laptops. With LDR switches, the issues associated with wiring complexity are avoided. These switches do not require DC biasing circuitry. However, it is important to note that LDR switches have limitations too, such as slower response times compared to electronic switches, and sensitivity to ambient light conditions.

An EBG structure is printed on the upper surface of the antenna array to reduce the mutual coupling effects between the radiating elements and improve the radiation characteristics of the array. The proposed EBG structure consists of
are achieved with low separation gaps between antenna elements (about $\lambda_o$/16 at 3.5 GHz). It is shown that the array's operational bands centered at 3.5 GHz and 4.65 GHz can be selected by activating certain LDR switches. The electromagnetic exposure of the array on the human body is investigated by determining the specific absorption rate (SAR). It is found that the proposed antenna shows lower SAR values compared to other antennas reported in literature. With the proposed EBG structure, the gain of the array is increased 7.5 dB (from -3.5 dBi to +4 dBi) at 3.5 GHz and by 14.3 dB (from -8.7 dBi to + 5.6 dBi) at 4.65 GHz. The average radiation efficiency between 3.5 GHz and 5.5 GHz increased by 42% from 20% to 62%. Excellent radiation characteristics of the EBG array makes it suitable for 5G portable devices such as tablets.

**INDEX TERMS** Electromagnetic Band Gap (EBG), multiple-input multiple-output (MIMO), 5G system, antenna arrays, specific absorption rate (SAR), photosensitive light dependent resistor (LDR).

# I. INTRODUCTION

Over the last decade, wireless communication technology has undergone rapid advancements, leading to increased demand for higher channel capacity and lower bit error rates [1]. Multiple-Input Multiple-Output (MIMO) is a crucial technology that has significantly contributed to address these demands [2]. These developments have improved various aspects of wireless communications including signal quality, enhanced throughputs, quality of service (QoS), minimizing fading effects, reduced latency, improved coverage, and energy efficiency [3], [4]. The reconfiguration mechanism applied to the MIMO antenna permits wireless systems to dynamically adjust and adapt to different communication scenarios, frequencies, or conditions [5]. This flexibility offers several benefits and advantages in terms of frequency agility, spectrum efficiency, interference mitigation, and adaptive beamforming [6]. It should be noted that the surrounding environment of a MIMO antenna system plays a crucial role in determining its gain characteristics, particularly in the context of reconfigurable antennas [7].

Coplanar waveguide (CPW) antennas have the advantages of easy fabrication, low cost, compact size, and multiband operation [8]. Synthetic metamaterial surfaces such as soft and hard surface defects, frequency selective surfaces, artificial magnetic conductors, and Electromagnetic Band Gap (EBG) structures have been widely used to replace traditional conductors in most microwave structures [9]. These technologies are widely used for suppressing surface waves between antenna elements [10].

EBG structures are engineered periodic arrays of dielectrics or metals that exhibit photonic band gap ranges where electromagnetic waves are prohibited from propagating through the material. These structures are designed to control the behavior of electromagnetic waves by creating stopbands in the frequency spectrum [11], [12]. EBG structures have been utilized for a variety of applications. Enhancing antenna gain and bandwidth are among the significant benefits they offer [13].

In 5G networks, 3GPP classifies the two main communication bands as FR1 (below 7.125 GHz) and FR2 (above 24.25 GHz) [14]. The use of millimeter-wave (mmW) spectrum results in significant reduction of antenna size because of the shorter wavelength and increase in bandwidth [15].

However, the propagation of mmW through buildings becomes extremely difficult since the skin depth and attenuation increase with increasing frequency [16], [17]. Sub-6 GHz frequencies remain crucial for achieving reliable coverage, while higher-frequency millimeter waves offer high-capacity solutions for open areas [18], [19].

In this paper, a reconfigurable MIMO antenna array with LDR switches is designed for 5G Applications. Isolation between the radiating elements of the MIMO array is enhanced by embedding EBG strips. The radiating elements consist of a monopole that is fed through a CPW structure, and the RF energy is launched through a matching load circuit and L-shaped reflector. By controlling the operation of LDR switches on the antenna, the proposed MIMO array provides reconfigurability and excellent radiation patterns.

# II. ANTENNA ARRAY STRUCTURE

The proposed MIMO antenna array, which is shown in Fig. 1, is designed to operate at sub-6GHz frequencies. Each antenna element consists of a monopole fed by a CPW port. The antenna ground-plane, which is an L-shaped reflector, is used to direct the radiation in a specific direction. An impedance matching structure, which is constructed from the first order Minkowski fractal, is inductively coupled to the radiating element to improve the array's bandwidth performance. The matching structure is attached to the L-shaped reflecting structure via four LDR switches that control the antenna surface current distribution and thereby its reconfigurability. All antenna elements were fabricated on an FR4 substrate having dielectric constant ($\epsilon_r$) of 4.3 and loss-tangent ($\tan\delta$) of 0.025.

The physical size of the array is 64×64 × 1.6 mm³ which is suitable for tablets and laptops. With LDR switches, the issues associated with wiring complexity are avoided. These switches do not require DC biasing circuitry. However, it is important to note that LDR switches have limitations too, such as slower response times compared to electronic switches, and sensitivity to ambient light conditions.

An EBG structure is printed on the upper surface of the antenna array to reduce the mutual coupling effects between the radiating elements and improve the radiation characteristics of the array. The proposed EBG structure consists of
<figure><img src="image_3.png" /><figcaption>FIGURE 1. Geometrical details of the MIMO antenna.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>FIGURE 2. Proposed EBG structure.</figcaption></figure>

<table><caption>TABLE 1. Parameters of the EBG structure.</caption><thead><tr><td>Parameter</td><td>Magnitude (mm)</td></tr></thead><tbody><tr><td>L<sub>EBG</sub></td><td>38.0</td></tr><tr><td>W<sub>EBG</sub></td><td>3.0</td></tr><tr><td>D<sub>L</sub></td><td>1.5</td></tr><tr><td>S<sub>L</sub></td><td>6.0</td></tr><tr><td>S<sub>W</sub></td><td>2.6</td></tr></tbody></table>

five elliptically shaped slots, as illustrated in Fig.2. Physical parameters defining the EBG strip are given in Table 1.

### III. CHARACTERIZATION OF EBG STRUCTURE

The defects on the copper strip of the EBG structure will have an influence on the array performance. Therefore, it is necessary to carry out a parametric study using numerical and analytical circuit modelling techniques to characterize the EBG structure.

#### A. NUMBER OF SLOTS

The number of slots on the EBG structure will have an impact on the resonance characteristics of the structure. The EBG structure was numerically analyzed using a commercially available full-wave analysis tool. The effect on the reflection and transmission coefficient responses is observed. An analysis is carried out by implementing the EBG on a 50-Ω microstrip transmission line, as shown in Fig.3. The transmission line is constructed on FR4 substrate. The propagating mode over the transmission line used is a quasi-Transverse

<figure><img src="image_5.png" /><figcaption>FIGURE 3. Performance analysis scenario for the EBG structure. EBG defects are loaded to a transmission line structure.</figcaption></figure>

Electromagnetic Mode (TEM) which is one of the primary modes of propagation in microstrip transmission lines.

The reflection coefficient ($S_{11}$) and transmission coefficient ($S_{21}$) responses as the function of frequency and number of slots (N) are given in Fig.4. It is observed that the EBG structure with N slots provides multiple resonances at sub-6 GHz band. The $S_{11}$ response defines the resonance bands in the EM spectrum that are prone to mutual coupling effects.

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /><figcaption>FIGURE 4. Scattering parameters of the EBG structure with different number of slots, (a) $S_{11}$, and (b) $S_{21}$.</figcaption></figure>

The $S_{21}$ response in Fig.4(b) indicates regions in the EM spectrum where rejection is the strongest. The EBG structure with five elliptically shaped slots impedes the propagation of surface waves, and this effect is observed in the transmission coefficient response with distinct attenuations at 2.45 GHz, 3.5 GHz, 4.65 GHz, and 5.8 GHz. The attenuation at 3.5 GHz and 4.65 GHz is instrumental in isolating EM interaction between the neighboring antennas in the proposed antenna
<figure><img src="image_3.png" /><figcaption>FIGURE 1. Geometrical details of the MIMO antenna.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>FIGURE 2. Proposed EBG structure.</figcaption></figure>

<table><caption>TABLE 1. Parameters of the EBG structure.</caption><thead><tr><td>Parameter</td><td>Magnitude (mm)</td></tr></thead><tbody><tr><td>L<sub>EBG</sub></td><td>38.0</td></tr><tr><td>W<sub>EBG</sub></td><td>3.0</td></tr><tr><td>D<sub>L</sub></td><td>1.5</td></tr><tr><td>S<sub>L</sub></td><td>6.0</td></tr><tr><td>S<sub>W</sub></td><td>2.6</td></tr></tbody></table>

five elliptically shaped slots, as illustrated in Fig.2. Physical parameters defining the EBG strip are given in Table 1.

### III. CHARACTERIZATION OF EBG STRUCTURE

The defects on the copper strip of the EBG structure will have an influence on the array performance. Therefore, it is necessary to carry out a parametric study using numerical and analytical circuit modelling techniques to characterize the EBG structure.

#### A. NUMBER OF SLOTS

The number of slots on the EBG structure will have an impact on the resonance characteristics of the structure. The EBG structure was numerically analyzed using a commercially available full-wave analysis tool. The effect on the reflection and transmission coefficient responses is observed. An analysis is carried out by implementing the EBG on a 50-Ω microstrip transmission line, as shown in Fig.3. The transmission line is constructed on FR4 substrate. The propagating mode over the transmission line used is a quasi-Transverse

<figure><img src="image_5.png" /><figcaption>FIGURE 3. Performance analysis scenario for the EBG structure. EBG defects are loaded to a transmission line structure.</figcaption></figure>

Electromagnetic Mode (TEM) which is one of the primary modes of propagation in microstrip transmission lines.

The reflection coefficient ($S_{11}$) and transmission coefficient ($S_{21}$) responses as the function of frequency and number of slots (N) are given in Fig.4. It is observed that the EBG structure with N slots provides multiple resonances at sub-6 GHz band. The $S_{11}$ response defines the resonance bands in the EM spectrum that are prone to mutual coupling effects.

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /><figcaption>FIGURE 4. Scattering parameters of the EBG structure with different number of slots, (a) $S_{11}$, and (b) $S_{21}$.</figcaption></figure>

The $S_{21}$ response in Fig.4(b) indicates regions in the EM spectrum where rejection is the strongest. The EBG structure with five elliptically shaped slots impedes the propagation of surface waves, and this effect is observed in the transmission coefficient response with distinct attenuations at 2.45 GHz, 3.5 GHz, 4.65 GHz, and 5.8 GHz. The attenuation at 3.5 GHz and 4.65 GHz is instrumental in isolating EM interaction between the neighboring antennas in the proposed antenna
array. EBG with 5 slots is considered in the proposed antenna array.

## B. GEOMETRY OF THE SLOTS

An analysis for the slot geometry is carried out, considering various slot shapes, including elliptical, rectangular, and circular. The effects of slot shape on transmission and reflection characteristics are shown in Fig. 5. The analysis results reveal that the elliptical slot exhibits exemplary matching performance compared to circular and rectangular-shaped slots. This is attributed to the motion of the currents at the edges of the elliptical slot, which effectively reduces reactance of the structure in comparison to the other geometries.

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /><figcaption>FIGURE 5. Scattering parameters of the EBG structure with different slot shapes, (a) $S_{11}$, and (b) $S_{21}$.</figcaption></figure>

## C. CIRCUIT MODEL

The performance of the proposed EBG is validated by analyzing its equivalent circuit model. The model is verified with two commercially software, Advanced Design System (ADS) by Keysight Technologies and High Frequency Structure Simulator (HFSS), which is a full-wave 3D electromagnetic (EM) simulation software by Ansys. Fig. 6 shows the electrical circuit model of the transmission line EBG structure. The microstrip stub of the T-shaped structure consists of parallel $C_T L_T$ circuit in series with parallel LCR circuit that represent the slots embedded in the stub. The coupling effect between the slots in the stub is represented by reactive elements $C_T$ and $L_T$. The values of the circuit elements are determined using ADS and are listed in Table 2. S-parameter responses of the equivalent circuit model along with the responses from ADS and HFSS are shown in Fig. 7. The excellent

<figure><img src="image_10.png" /><figcaption>FIGURE 6. Equivalent circuit model of the five slot EBG structure.</figcaption></figure>

<table><caption>TABLE 2. Circuit elements of the equivalent circuit model.</caption><thead><tr><th>Lumped element</th><th>Value</th><th>Lumped element</th><th>Value</th></tr></thead><tbody><tr><td>R</td><td>50 Ω</td><td>C<sub>T3</sub></td><td>0.64 pF</td></tr><tr><td>L</td><td>0.1 nH</td><td>L<sub>T3</sub></td><td>2.06 nH</td></tr><tr><td>L<sub>T</sub></td><td>42.6 nH</td><td>C<sub>T4</sub></td><td>1.04 pF</td></tr><tr><td>R<sub>T</sub></td><td>50 Ω</td><td>L<sub>T4</sub></td><td>0.64 nH</td></tr><tr><td>C<sub>T1</sub></td><td>0.45 pF</td><td>C<sub>T5</sub></td><td>2.04 pF</td></tr><tr><td>L<sub>T1</sub></td><td>1.94 nH</td><td>L<sub>T5</sub></td><td>0.2 nH</td></tr><tr><td>C<sub>T2</sub></td><td>1.54 pF</td><td>C</td><td>0.08 pF</td></tr><tr><td>L<sub>T2</sub></td><td>1.42 nH</td><td>C<sub>F</sub></td><td>0.2 pF</td></tr></tbody></table>

correlation in the S-parameter responses of the circuit model with ADS and HFSS confirms the accuracy of the electrical model.

## IV. ANTENNA PERFORMANCE

The EBG structure, which is located at the center of the 2 × 2 MIMO antenna array, has a great impact on the antenna performance. In this section, firstly, the effect of the EBG structure on the radiation characteristics is investigated. Then, a beam switching implementation is demonstrated using LDR switches.

### A. PERFORMANCE WITHOUT EBG

This section presents the numerical analysis results of the antenna array without the EBG structure obtained using CST Studio Suite [15], which is a high-performance 3D electromagnetic analysis software. The reflection coefficient response of the antenna array and radiation patterns in the E and H orthogonal planes are given in Fig. 8. The reflection coefficient response shows that the proposed antenna array resonates more strongly at 3.5 GHz and 4.8 GHz. It is lower than −10 dB within the range of 3.4-3.6 GHz and 4.25-5.2 GHz. Moreover, at 3.5 GHz the radiation patterns in both E- and H-planes can be approximated to an oval shape, and at 4.65 GHz the array in the E-plane radiates
array. EBG with 5 slots is considered in the proposed antenna array.

## B. GEOMETRY OF THE SLOTS

An analysis for the slot geometry is carried out, considering various slot shapes, including elliptical, rectangular, and circular. The effects of slot shape on transmission and reflection characteristics are shown in Fig. 5. The analysis results reveal that the elliptical slot exhibits exemplary matching performance compared to circular and rectangular-shaped slots. This is attributed to the motion of the currents at the edges of the elliptical slot, which effectively reduces reactance of the structure in comparison to the other geometries.

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /><figcaption>FIGURE 5. Scattering parameters of the EBG structure with different slot shapes, (a) $S_{11}$, and (b) $S_{21}$.</figcaption></figure>

## C. CIRCUIT MODEL

The performance of the proposed EBG is validated by analyzing its equivalent circuit model. The model is verified with two commercially software, Advanced Design System (ADS) by Keysight Technologies and High Frequency Structure Simulator (HFSS), which is a full-wave 3D electromagnetic (EM) simulation software by Ansys. Fig. 6 shows the electrical circuit model of the transmission line EBG structure. The microstrip stub of the T-shaped structure consists of parallel $C_T L_T$ circuit in series with parallel LCR circuit that represent the slots embedded in the stub. The coupling effect between the slots in the stub is represented by reactive elements $C_T$ and $L_T$. The values of the circuit elements are determined using ADS and are listed in Table 2. S-parameter responses of the equivalent circuit model along with the responses from ADS and HFSS are shown in Fig. 7. The excellent

<figure><img src="image_10.png" /><figcaption>FIGURE 6. Equivalent circuit model of the five slot EBG structure.</figcaption></figure>

<table><caption>TABLE 2. Circuit elements of the equivalent circuit model.</caption><thead><tr><th>Lumped element</th><th>Value</th><th>Lumped element</th><th>Value</th></tr></thead><tbody><tr><td>R</td><td>50 Ω</td><td>C<sub>T3</sub></td><td>0.64 pF</td></tr><tr><td>L</td><td>0.1 nH</td><td>L<sub>T3</sub></td><td>2.06 nH</td></tr><tr><td>L<sub>T</sub></td><td>42.6 nH</td><td>C<sub>T4</sub></td><td>1.04 pF</td></tr><tr><td>R<sub>T</sub></td><td>50 Ω</td><td>L<sub>T4</sub></td><td>0.64 nH</td></tr><tr><td>C<sub>T1</sub></td><td>0.45 pF</td><td>C<sub>T5</sub></td><td>2.04 pF</td></tr><tr><td>L<sub>T1</sub></td><td>1.94 nH</td><td>L<sub>T5</sub></td><td>0.2 nH</td></tr><tr><td>C<sub>T2</sub></td><td>1.54 pF</td><td>C</td><td>0.08 pF</td></tr><tr><td>L<sub>T2</sub></td><td>1.42 nH</td><td>C<sub>F</sub></td><td>0.2 pF</td></tr></tbody></table>

correlation in the S-parameter responses of the circuit model with ADS and HFSS confirms the accuracy of the electrical model.

## IV. ANTENNA PERFORMANCE

The EBG structure, which is located at the center of the 2 × 2 MIMO antenna array, has a great impact on the antenna performance. In this section, firstly, the effect of the EBG structure on the radiation characteristics is investigated. Then, a beam switching implementation is demonstrated using LDR switches.

### A. PERFORMANCE WITHOUT EBG

This section presents the numerical analysis results of the antenna array without the EBG structure obtained using CST Studio Suite [15], which is a high-performance 3D electromagnetic analysis software. The reflection coefficient response of the antenna array and radiation patterns in the E and H orthogonal planes are given in Fig. 8. The reflection coefficient response shows that the proposed antenna array resonates more strongly at 3.5 GHz and 4.8 GHz. It is lower than −10 dB within the range of 3.4-3.6 GHz and 4.25-5.2 GHz. Moreover, at 3.5 GHz the radiation patterns in both E- and H-planes can be approximated to an oval shape, and at 4.65 GHz the array in the E-plane radiates
<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /><figcaption>FIGURE 7. Equivalent circuit model analysis results, (a) S<sub>11</sub>, and (b) S<sub>21</sub>.</figcaption></figure>

<table><caption>TABLE 3. Comparison of performance parameters of the array with and without EBG.</caption><thead><tr><th></th><th>S<sub>11</sub><br>(dB)</th><th>Gain<br>(dBi)</th><th>Eff.<br>(%)</th></tr></thead><tbody><tr><td>Without EBG @3.5 GHz</td><td>-20</td><td>-3.5</td><td>20</td></tr><tr><td>Without EBG @4.65 GHz</td><td>-12</td><td>-8.7</td><td>20</td></tr><tr><td>With EBG @3.5 GHz</td><td>-27</td><td>4</td><td>63</td></tr><tr><td>With EBG @4.65 GHz</td><td>-22</td><td>5.6</td><td>61</td></tr></tbody></table>

approximately omnidirectionally whereas in the H-plane it is bidirectional firing at angles of 25 and 155 degrees, as shown in Fig. 8(b) and (c), respectively.

The transmission coefficient response of the antenna array is given in Fig. 9(a). The isolation between the ports is better than 15 dB in the 1-6 GHz frequency range. Antenna gain and radiation efficiency of the array are shown in Fig. 9(b) and (c), respectively. Fig. 9(b) shows that the gain of the array over 3-6 GHz varies between -8.7 dBi and -2.5 dBi. Fig. 9(c) shows that the radiation efficiency of the array without EBG varies between 15% and 21%. The poor gain and radiation efficiency is due to the detrimental effects of mutual coupling between the radiating elements of the array. Effective design and mitigation strategies are therefore essential to counteract these effects and achieve the desired array performance.

## B. PERFORMANCE WITH EBG

EBG structure is implemented between the radiating elements to prevent the electromagnetic interference between adjacent antenna elements in an array. The proposed EBG structure also prevents propagation of the surface waves which are generated by reflections and interactions with the

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /><figcaption>FIGURE 8. (a) Reflection coefficient response without EBG structure, (b) far-field radiation patterns of the antenna array without EBG structure in the E-plane and H-plane at 3.5 GHz, and (c) far-field radiation patterns of the antenna array without EBG structure in the E-plane and H-plane at 4.65 GHz.</figcaption></figure>

ground plane. These surface waves can also degrade the performance of the antenna system by interfering with the desired radiation pattern and causing scattering. Fig. 10 shows that by inserting the EBG between the radiating elements, significant improvement in the reflection coefficient response and radiation patterns is obtained. The reflection coefficient is lower than -10 dB in the range of 3.4-3.6 GHz and 4.25-5.2 GHz. At 3.5 GHz, the reflection coefficient is -27 dB, and at 4.65 GHz it is -22 dB. The proposed EBG structure creates a more conducive electromagnetic environment around the antenna elements, which in turn contributes to mitigating factors that improve impedance matching. The radiation patterns at 3.5 GHz in E- and H-planes are approximately oval shaped, and at 4.5 GHz the radiation in the E- and H-planes is approximately omnidirectional but with a pinch off at 90°.

The transmission coefficient response of the antenna array with EBG structure is given in Fig. 11(a). It shows that
<figure><img src="image_11.png" /></figure>

<figure><img src="image_12.png" /><figcaption>FIGURE 7. Equivalent circuit model analysis results, (a) S<sub>11</sub>, and (b) S<sub>21</sub>.</figcaption></figure>

<table><caption>TABLE 3. Comparison of performance parameters of the array with and without EBG.</caption><thead><tr><th></th><th>S<sub>11</sub><br>(dB)</th><th>Gain<br>(dBi)</th><th>Eff.<br>(%)</th></tr></thead><tbody><tr><td>Without EBG @3.5 GHz</td><td>-20</td><td>-3.5</td><td>20</td></tr><tr><td>Without EBG @4.65 GHz</td><td>-12</td><td>-8.7</td><td>20</td></tr><tr><td>With EBG @3.5 GHz</td><td>-27</td><td>4</td><td>63</td></tr><tr><td>With EBG @4.65 GHz</td><td>-22</td><td>5.6</td><td>61</td></tr></tbody></table>

approximately omnidirectionally whereas in the H-plane it is bidirectional firing at angles of 25 and 155 degrees, as shown in Fig. 8(b) and (c), respectively.

The transmission coefficient response of the antenna array is given in Fig. 9(a). The isolation between the ports is better than 15 dB in the 1-6 GHz frequency range. Antenna gain and radiation efficiency of the array are shown in Fig. 9(b) and (c), respectively. Fig. 9(b) shows that the gain of the array over 3-6 GHz varies between -8.7 dBi and -2.5 dBi. Fig. 9(c) shows that the radiation efficiency of the array without EBG varies between 15% and 21%. The poor gain and radiation efficiency is due to the detrimental effects of mutual coupling between the radiating elements of the array. Effective design and mitigation strategies are therefore essential to counteract these effects and achieve the desired array performance.

## B. PERFORMANCE WITH EBG

EBG structure is implemented between the radiating elements to prevent the electromagnetic interference between adjacent antenna elements in an array. The proposed EBG structure also prevents propagation of the surface waves which are generated by reflections and interactions with the

<figure><img src="image_13.png" /></figure>

<figure><img src="image_14.png" /></figure>

<figure><img src="image_15.png" /><figcaption>FIGURE 8. (a) Reflection coefficient response without EBG structure, (b) far-field radiation patterns of the antenna array without EBG structure in the E-plane and H-plane at 3.5 GHz, and (c) far-field radiation patterns of the antenna array without EBG structure in the E-plane and H-plane at 4.65 GHz.</figcaption></figure>

ground plane. These surface waves can also degrade the performance of the antenna system by interfering with the desired radiation pattern and causing scattering. Fig. 10 shows that by inserting the EBG between the radiating elements, significant improvement in the reflection coefficient response and radiation patterns is obtained. The reflection coefficient is lower than -10 dB in the range of 3.4-3.6 GHz and 4.25-5.2 GHz. At 3.5 GHz, the reflection coefficient is -27 dB, and at 4.65 GHz it is -22 dB. The proposed EBG structure creates a more conducive electromagnetic environment around the antenna elements, which in turn contributes to mitigating factors that improve impedance matching. The radiation patterns at 3.5 GHz in E- and H-planes are approximately oval shaped, and at 4.5 GHz the radiation in the E- and H-planes is approximately omnidirectional but with a pinch off at 90°.

The transmission coefficient response of the antenna array with EBG structure is given in Fig. 11(a). It shows that
<figure><img src="image_16.png" /></figure>

<figure><img src="image_17.png" /></figure>

<figure><img src="image_18.png" /><figcaption>**FIGURE 9.** Transmission coefficient response of the antenna array without EBG structure, (b) antenna gain without EBG structure, and (c) radiation efficiency without EBG structure.</figcaption></figure>

the isolation between the ports is better than 21 dB in the 1-6 GHz frequency range. Fig. 11(b) shows gain of the array over 3-6 GHz varies between 1 dBi and 5.6 dBi. The radiation efficiency of the array, shown in Fig. 11(c), varies between 37.5% and 61% over the 3-6 GHz band. The significant characteristics of the antenna array without and with EBG structure at 3.5 GHz and 4.65 GHz are summarized in Table 3.

### C. EFFECTS OF LDR SWITCHING

Four light dependent resistor switches are added to each fractal structure as shown in Fig. 12(a). In this application the LDR was either fully activated or deactivated. In this scenario the LDR were not used in a quasi-ON/OFF mode. By activating or deactivating the LDR switches, each radiating element in the array can be controlled. The simulated reflection and transmission coefficient responses when LDR switches are activated (ON status) are shown in Fig. 12(a) and (b), respectively. The reflection coefficient is

<figure><img src="image_19.png" /></figure>

<figure><img src="image_20.png" /></figure>

<figure><img src="image_21.png" /><figcaption>**FIGURE 10.** Antenna performance: (a) Return loss with EBG structure, (b) Far-field radiation patterns in the E- and H-planes at 3.5 GHz, and (c) Far-field radiation patterns in the E- and H-planes at 4.65 GHz.</figcaption></figure>

better than -10 dB across 3.3-3.5 GHz and 4.3-5.1 GHz. At 3.5 GHz, the reflection coefficient is -14 dB, and at 4.65 GHz it is -25 dB. The isolation between the ports is better than 21 dB within 1-6 GHz frequency range. The radiation patterns in the E- and H-planes are shown in Fig. 12(c) at 3.5 GHz and 4.65 GHz. The array radiates over 0° to -180° in both the E- and H-planes at 3.5 GHz. At 4.65 GHz, it radiates in the opposite direction over 0° to +180° in both the E- and H-planes. When the LDR switches are deactivated (OFF state) the performance of the antenna array is identical to those shown in Fig. 10.

By turning certain elements ON or OFF using the LDR switches, the overall radiation pattern of the antenna array can be controlled. This enables the ability to electronically steer the direction of the main beam, which is very useful for applications like radar, wireless communication, and satellite communication.

Traditional mechanical steering mechanisms require moving parts, which can be bulky and have limitations in terms of speed and accuracy. LDR-based beamforming eliminates
<figure><img src="image_16.png" /></figure>

<figure><img src="image_17.png" /></figure>

<figure><img src="image_18.png" /><figcaption>**FIGURE 9.** Transmission coefficient response of the antenna array without EBG structure, (b) antenna gain without EBG structure, and (c) radiation efficiency without EBG structure.</figcaption></figure>

the isolation between the ports is better than 21 dB in the 1-6 GHz frequency range. Fig. 11(b) shows gain of the array over 3-6 GHz varies between 1 dBi and 5.6 dBi. The radiation efficiency of the array, shown in Fig. 11(c), varies between 37.5% and 61% over the 3-6 GHz band. The significant characteristics of the antenna array without and with EBG structure at 3.5 GHz and 4.65 GHz are summarized in Table 3.

### C. EFFECTS OF LDR SWITCHING

Four light dependent resistor switches are added to each fractal structure as shown in Fig. 12(a). In this application the LDR was either fully activated or deactivated. In this scenario the LDR were not used in a quasi-ON/OFF mode. By activating or deactivating the LDR switches, each radiating element in the array can be controlled. The simulated reflection and transmission coefficient responses when LDR switches are activated (ON status) are shown in Fig. 12(a) and (b), respectively. The reflection coefficient is

<figure><img src="image_19.png" /></figure>

<figure><img src="image_20.png" /></figure>

<figure><img src="image_21.png" /><figcaption>**FIGURE 10.** Antenna performance: (a) Return loss with EBG structure, (b) Far-field radiation patterns in the E- and H-planes at 3.5 GHz, and (c) Far-field radiation patterns in the E- and H-planes at 4.65 GHz.</figcaption></figure>

better than -10 dB across 3.3-3.5 GHz and 4.3-5.1 GHz. At 3.5 GHz, the reflection coefficient is -14 dB, and at 4.65 GHz it is -25 dB. The isolation between the ports is better than 21 dB within 1-6 GHz frequency range. The radiation patterns in the E- and H-planes are shown in Fig. 12(c) at 3.5 GHz and 4.65 GHz. The array radiates over 0° to -180° in both the E- and H-planes at 3.5 GHz. At 4.65 GHz, it radiates in the opposite direction over 0° to +180° in both the E- and H-planes. When the LDR switches are deactivated (OFF state) the performance of the antenna array is identical to those shown in Fig. 10.

By turning certain elements ON or OFF using the LDR switches, the overall radiation pattern of the antenna array can be controlled. This enables the ability to electronically steer the direction of the main beam, which is very useful for applications like radar, wireless communication, and satellite communication.

Traditional mechanical steering mechanisms require moving parts, which can be bulky and have limitations in terms of speed and accuracy. LDR-based beamforming eliminates
<figure><img src="image_22.png" /></figure>

<figure><img src="image_23.png" /></figure>

<figure><img src="image_24.png" /><figcaption>**FIGURE 11.** Antenna array performance with EBG structure, (a) Transmission coefficient response, (b) Antenna gain, and (c) Radiation efficiency.</figcaption></figure>

the need for such mechanisms, reducing the complexity and maintenance requirements of the antenna system.

Envelope Correlation Coefficient (ECC) is a parameter used to characterize the performance of MIMO antenna arrays [14]. It measures the correlation between the envelope of the signals received by the various antennas in a MIMO system. ECC values close to zero indicate that the signals received by different antennas are relatively uncorrelated, which is beneficial for achieving the full potential of MIMO technology, including improved spatial diversity and higher data rates. Fig. 13(a) shows the magnitude of the ECC of the proposed MIMO antenna array over the frequency span of interest is less than 0.2. These results can be explained by studying the surface current density distribution over the antenna array at 3.5 GHz and 4.65 GHz. The surface current distribution of the antenna array at these frequencies is shown in Fig. 13(b) and (c). It shows the effectiveness of the EBG

<figure><img src="image_25.png" /></figure>

<figure><img src="image_26.png" /></figure>

<figure><img src="image_27.png" /></figure>

<figure><img src="image_28.png" /><figcaption>**FIGURE 12.** Performance of the reconfigurable MIMO antenna, (a) Reflection coefficient response, (b) Transmission coefficient response, (c) Radiation patterns at 3.5 GHz, and (d) Radiation patterns at 4.65 GHz.</figcaption></figure>

structure in blocking mutual coupling between the radiating elements. The EBG structure induces a phase difference in the propagation of electromagnetic waves between neighboring radiating elements, leading to an amplification of current intensity along the edges of the substrate.

## V. MEASURED RESULTS AND DISCUSSION

The prototype of the MIMO antenna array shown in Fig. 14 is fabricated on FR4 substrate. Its S-parameters and radiation patterns are measured using Agilent PNA 8720 Network Analyzer. The measured results are compared with the results
<figure><img src="image_22.png" /></figure>

<figure><img src="image_23.png" /></figure>

<figure><img src="image_24.png" /><figcaption>**FIGURE 11.** Antenna array performance with EBG structure, (a) Transmission coefficient response, (b) Antenna gain, and (c) Radiation efficiency.</figcaption></figure>

the need for such mechanisms, reducing the complexity and maintenance requirements of the antenna system.

Envelope Correlation Coefficient (ECC) is a parameter used to characterize the performance of MIMO antenna arrays [14]. It measures the correlation between the envelope of the signals received by the various antennas in a MIMO system. ECC values close to zero indicate that the signals received by different antennas are relatively uncorrelated, which is beneficial for achieving the full potential of MIMO technology, including improved spatial diversity and higher data rates. Fig. 13(a) shows the magnitude of the ECC of the proposed MIMO antenna array over the frequency span of interest is less than 0.2. These results can be explained by studying the surface current density distribution over the antenna array at 3.5 GHz and 4.65 GHz. The surface current distribution of the antenna array at these frequencies is shown in Fig. 13(b) and (c). It shows the effectiveness of the EBG

<figure><img src="image_25.png" /></figure>

<figure><img src="image_26.png" /></figure>

<figure><img src="image_27.png" /></figure>

<figure><img src="image_28.png" /><figcaption>**FIGURE 12.** Performance of the reconfigurable MIMO antenna, (a) Reflection coefficient response, (b) Transmission coefficient response, (c) Radiation patterns at 3.5 GHz, and (d) Radiation patterns at 4.65 GHz.</figcaption></figure>

structure in blocking mutual coupling between the radiating elements. The EBG structure induces a phase difference in the propagation of electromagnetic waves between neighboring radiating elements, leading to an amplification of current intensity along the edges of the substrate.

## V. MEASURED RESULTS AND DISCUSSION

The prototype of the MIMO antenna array shown in Fig. 14 is fabricated on FR4 substrate. Its S-parameters and radiation patterns are measured using Agilent PNA 8720 Network Analyzer. The measured results are compared with the results
<figure><img src="image_29.png" /></figure>

<figure><img src="image_30.png" /></figure>

<figure><img src="image_31.png" /><figcaption>**FIGURE 13.** Performance of the proposed reconfigurable MIMO array, (a) ECC response, (b) Current density distribution over the antenna array at 3.5 GHz, and (c) Current density distribution over the antenna array at 4.65 GHz.</figcaption></figure>

obtained by CST Studio Suite to verify the accuracy and effectiveness of the simulation tool. The LDR switches were covered with an opaque lid so that they were inactive during the measurements. The radiation patterns were measured inside an RF anechoic chamber in the two principal planes.

The reflection and transmission coefficient responses of the antenna array with LDR switches OFF are shown in Fig.15(a) and (b), respectively. The measured reflection coefficient is better than -10 dB across 3.3-3.6 GHz and 4.2-5.1 GHz. At 3.5 GHz, the reflection coefficient is -25 dB, and at 4.65 GHz it is -25 dB. The isolation between the radiating elements is better than 35 dB within 1-6 GHz range. The radiation patterns in the E- and H-planes at 3.5 GHz and 4.65 GHz are shown in Fig.15(c) and (d). At 3.5 GHz, the array radiates over 0° to -180° in the

<figure><img src="image_32.png" /><figcaption>(a)</figcaption></figure>

<figure><img src="image_33.png" /><figcaption>(b)</figcaption></figure>

<caption>**FIGURE 14.** Fabricated prototype of the reconfigurable MIMO antenna (a) Top and bottom view, (b) Prototype in the measurement setup.</caption>

E-plane and in the H-plane the array radiates over 0° to +180°. At 4.65 GHz the array radiates bidirectionally at 27° and 158° in the E-plane, and at over 0° to +180° in the H-plane. There is excellent agreement between simulated and measured results. The discrepancies between simulated and measured results are attributed to manufacturing tolerances and environmental conditions.

The MIMO antenna array's performance was evaluated when all LDR switches were activated ON. Fig.16 shows the measured reflection and transmission responses of the array. $S_{11}$ is lower than -10 dB between 3.25-3.5 GHz and 4.2-5.1 GHz. At 3.4 GHz, $S_{11}$ is -15 dB, and at 4.65 GHz it is -30 dB. The $S_{21}$ between the radiating elements is greater than 38 dB over 1-6 GHz. At 3.5 GHz, the array radiates over 0° to -180° in the E-plane and bidirectionally at angles of -30° and -160° in the H-plane. At 4.65 GHz the array radiates over 0° to +180° in the E-plane, and in the H-plane it radiates over 0° to +180°.

The reflection and transmission coefficients of the antenna array with all LDR switches either activated or deactivated are compared in Table 4. In the 'ON' condition the antenna is receptive to 4.65 GHz and in the 'OFF' state it is receptive to both 3.5 GHz and 4.65 GHz.
<figure><img src="image_29.png" /></figure>

<figure><img src="image_30.png" /></figure>

<figure><img src="image_31.png" /><figcaption>**FIGURE 13.** Performance of the proposed reconfigurable MIMO array, (a) ECC response, (b) Current density distribution over the antenna array at 3.5 GHz, and (c) Current density distribution over the antenna array at 4.65 GHz.</figcaption></figure>

obtained by CST Studio Suite to verify the accuracy and effectiveness of the simulation tool. The LDR switches were covered with an opaque lid so that they were inactive during the measurements. The radiation patterns were measured inside an RF anechoic chamber in the two principal planes.

The reflection and transmission coefficient responses of the antenna array with LDR switches OFF are shown in Fig.15(a) and (b), respectively. The measured reflection coefficient is better than -10 dB across 3.3-3.6 GHz and 4.2-5.1 GHz. At 3.5 GHz, the reflection coefficient is -25 dB, and at 4.65 GHz it is -25 dB. The isolation between the radiating elements is better than 35 dB within 1-6 GHz range. The radiation patterns in the E- and H-planes at 3.5 GHz and 4.65 GHz are shown in Fig.15(c) and (d). At 3.5 GHz, the array radiates over 0° to -180° in the

<figure><img src="image_32.png" /><figcaption>(a)</figcaption></figure>

<figure><img src="image_33.png" /><figcaption>(b)</figcaption></figure>

<caption>**FIGURE 14.** Fabricated prototype of the reconfigurable MIMO antenna (a) Top and bottom view, (b) Prototype in the measurement setup.</caption>

E-plane and in the H-plane the array radiates over 0° to +180°. At 4.65 GHz the array radiates bidirectionally at 27° and 158° in the E-plane, and at over 0° to +180° in the H-plane. There is excellent agreement between simulated and measured results. The discrepancies between simulated and measured results are attributed to manufacturing tolerances and environmental conditions.

The MIMO antenna array's performance was evaluated when all LDR switches were activated ON. Fig.16 shows the measured reflection and transmission responses of the array. $S_{11}$ is lower than -10 dB between 3.25-3.5 GHz and 4.2-5.1 GHz. At 3.4 GHz, $S_{11}$ is -15 dB, and at 4.65 GHz it is -30 dB. The $S_{21}$ between the radiating elements is greater than 38 dB over 1-6 GHz. At 3.5 GHz, the array radiates over 0° to -180° in the E-plane and bidirectionally at angles of -30° and -160° in the H-plane. At 4.65 GHz the array radiates over 0° to +180° in the E-plane, and in the H-plane it radiates over 0° to +180°.

The reflection and transmission coefficients of the antenna array with all LDR switches either activated or deactivated are compared in Table 4. In the 'ON' condition the antenna is receptive to 4.65 GHz and in the 'OFF' state it is receptive to both 3.5 GHz and 4.65 GHz.
<figure><img src="image_34.png" /></figure>

<figure><img src="image_35.png" /></figure>

<figure><img src="image_36.png" /></figure>

<figure><img src="image_37.png" /><figcaption>FIGURE 15. Antenna performance when all LDR switches are switched 'OFF', (a) Reflection coefficient, (b) Transmission coefficient, (c) Radiation patterns at 3.5 GHz, and (d) Radiation patterns at 4.65 GHz.</figcaption></figure>

<figure><img src="image_38.png" /></figure>

<figure><img src="image_39.png" /></figure>

<figure><img src="image_40.png" /></figure>

<figure><img src="image_41.png" /><figcaption>FIGURE 16. Antenna performance when all LDRs switches are switched 'ON', (a) Reflection coefficient, (b) Transmission coefficient, (c) Radiation patterns at 3.5 GHz, and (d) Radiation patterns at 4.65 GHz.</figcaption></figure>

## A. SAR ANALYSIS

Specific Absorption Rate (SAR) quantifies the pace at which body tissues absorb electromagnetic energy. It is quantified in terms of watts per kilogram (W/kg). SAR analysis is carried out on the proposed MIMO antenna array. Radiation effects are numerically evaluated by analyzing the SAR using HUGO which is standardized anatomical model of the head in CST Studio Suite. HUGO represents the human head and its

internal structures with high anatomical accuracy. Radiation absorption from the proposed antenna array is evaluated on HUGO in the ON/OFF state at 3.5 GHz and 4.65 GHz. In the proposed simulation scenario, the antenna array is located 10 mm away from HUGO's face. The power transmitted from the antenna array is 20 dBm, which falls within the Federal Communications Commission's (FCC) maximum permissible limit. The results of this simulation are shown in Fig. 17.
<figure><img src="image_34.png" /></figure>

<figure><img src="image_35.png" /></figure>

<figure><img src="image_36.png" /></figure>

<figure><img src="image_37.png" /><figcaption>FIGURE 15. Antenna performance when all LDR switches are switched 'OFF', (a) Reflection coefficient, (b) Transmission coefficient, (c) Radiation patterns at 3.5 GHz, and (d) Radiation patterns at 4.65 GHz.</figcaption></figure>

<figure><img src="image_38.png" /></figure>

<figure><img src="image_39.png" /></figure>

<figure><img src="image_40.png" /></figure>

<figure><img src="image_41.png" /><figcaption>FIGURE 16. Antenna performance when all LDRs switches are switched 'ON', (a) Reflection coefficient, (b) Transmission coefficient, (c) Radiation patterns at 3.5 GHz, and (d) Radiation patterns at 4.65 GHz.</figcaption></figure>

## A. SAR ANALYSIS

Specific Absorption Rate (SAR) quantifies the pace at which body tissues absorb electromagnetic energy. It is quantified in terms of watts per kilogram (W/kg). SAR analysis is carried out on the proposed MIMO antenna array. Radiation effects are numerically evaluated by analyzing the SAR using HUGO which is standardized anatomical model of the head in CST Studio Suite. HUGO represents the human head and its

internal structures with high anatomical accuracy. Radiation absorption from the proposed antenna array is evaluated on HUGO in the ON/OFF state at 3.5 GHz and 4.65 GHz. In the proposed simulation scenario, the antenna array is located 10 mm away from HUGO's face. The power transmitted from the antenna array is 20 dBm, which falls within the Federal Communications Commission's (FCC) maximum permissible limit. The results of this simulation are shown in Fig. 17.
<table><caption>**TABLE 4.** Comparison of antenna array parameters with LDR in the 'ON' and 'OFF' states.</caption><thead><tr><th></th><th>S<sub>11</sub><br>(dB)</th><th>S<sub>21</sub> & S<sub>12</sub><br>(dB)</th></tr></thead><tbody><tr><td>LDR switched OFF @3.5 GHz</td><td>-25</td><td>-38</td></tr><tr><td>LDR switched OFF @4.65 GHz</td><td>-25</td><td>-42</td></tr><tr><td>LDR switched ON @3.5 GHz</td><td>-15</td><td>-42</td></tr><tr><td>LDR switched ON @4.65 GHz</td><td>-30</td><td>-40</td></tr></tbody></table>

<table><caption>**TABLE 5.** Comparison with other MIMO antenna arrays published in literature.</caption><thead><tr><th>Ref.</th><th>Size<br>(λ<sub>o</sub><sup>2</sup>)</th><th>No.<br>radiating<br>elements</th><th>Freq.<br>(GHz)</th><th>Gain<br>(dBi)</th><th>Isolation<br>(dB)</th><th>ECC</th><th>Gap</th></tr></thead><tbody><tr><td>[20]</td><td>2.4×1.8</td><td>8</td><td>5.15/5.95</td><td>2.1</td><td>15</td><td>0.05</td><td>λ/1.9</td></tr><tr><td>[21]</td><td>2.75×1.4</td><td>4</td><td>5.15/5.85</td><td>1.9</td><td>16</td><td>0.06</td><td>λ/2</td></tr><tr><td>[22]</td><td>2.5×1.1</td><td>8</td><td>5.15/5.95</td><td>1.9</td><td>10</td><td>0.09</td><td>λ/2</td></tr><tr><td>[23]</td><td>2.5×1.2</td><td>12</td><td>4.8/5.1</td><td>2.6</td><td>12</td><td>---</td><td>λ/2.1</td></tr><tr><td>[24]</td><td>2.78×1.5</td><td>8</td><td>5.17/5.95</td><td>2.2</td><td>10</td><td>0.11</td><td>λ/2.3</td></tr><tr><td>[25]</td><td>2×2</td><td>4</td><td>3.3/5.8</td><td>1.1</td><td>15</td><td>0.10</td><td>λ/2.1</td></tr><tr><td>[26]</td><td>3×1.3</td><td>2</td><td>5.6/5.67</td><td>12</td><td>30</td><td>0.06</td><td>λ/1.4</td></tr><tr><td>This work</td><td>0.87×0.87</td><td>4</td><td>3.5/4.65</td><td>5.6</td><td>42</td><td>0.01</td><td>λ/8</td></tr></tbody></table>

<figure><img src="image_42.png" /><figcaption>**FIGURE 17.** Problem definition for the SAR analysis. Far-field radiation and SAR values at (a) 3.5 GHz, and (b) 4.65 GHz.</figcaption></figure>

When the LDR switches are in the 'OFF' state the peak value of the SAR is computed to be 0.15 W/kg at 3.5 GHz and 0.21 W/kg at 4.65 GHz. In the 'ON' state the SAR peak value is 1.25 W/kg at 3.5 GHz and 0.94 W/kg at 4.65 GHz. The magnitude of SAR is well below the limit permitted by the FCC in United States, which is 1.6 W/kg averaged over 1 gram of tissue for both head and body exposure. In the European Union, the limit is generally 2.0 W/kg averaged over 10 grams of tissue for head exposure and 2.0 W/kg averaged over 10 grams of tissue for body exposure.

## B. COMPARISON WITH OTHER MIMO ANTENNA ARRAYS

The performance of the proposed antenna array is compared with the other MIMO antenna arrays reported in literature in

Table 5. Compared to the other antenna arrays, the proposed antenna array exhibits better performance in terms of antenna gain, inter-radiating element isolation, and ECC. Moreover, the gap between the radiating elements and the overall array size is significantly smaller. Unlike other antenna arrays, the performance of the proposed array can be reconfigured with LDR switches without the need for DC biasing.

## VI. CONCLUSION

The proposed sub-6 GHz MIMO antenna array with EBG structure is shown to provide high element isolation. The reconfigurability property of the antenna array is also demonstrated using LDR switches. With the proposed EBG structure, the antenna gain of the array is increased by 7.5 dB to +4 dBi at 3.5 GHz and by 14.3 dB to +5.6 dBi at 4.65 GHz. The radiation efficiency at 3.5 GHz and 4.65 GHz are increased to 63% to 61%. This demonstrates the effectiveness of the proposed EBG structure. Moreover, the array exhibits excellent radiation characteristics with EBG. SAR of the antenna array was evaluated on HUGO which is standardized anatomical model of the head in CST Studio Suite. When the LDR switches on the antenna array were either switched 'ON' or 'OFF', the SAR peak value was well below 1.6 W/kg, which is the limit set by the FCC in United States.

## REFERENCES

[1] C. A. Balanis, *Antenna Theory Analysis and Design*, 2013.

[2] I. Ishteyaq and K. Muzaffar, "Multiple input multiple output (MIMO) and fifth generation (5G): An indispensable technology for sub-6 GHz and millimeter wave future generation mobile terminal applications," *Int. J. Microw. Wireless Technol.*, vol. 14, no. 7, pp. 932–948, Sep. 2022.

[3] C. G. Christodoulou, Y. Tawk, S. A. Lane, and S. R. Erwin, "Reconfigurable antennas for wireless and space applications," *Proc. IEEE*, vol. 100, no. 7, pp. 2250–2261, Jun. 2012.

[4] K. Bagadi, K. Sathish, M. Alibakhshikenari, B. S. Virdee, L. Kouhalvandi, K. N. Olan-Nuñez, G. Pau, C. H. See, I. Dayoub, P. Livreri, S. Aïssa, F. Falcone, and E. Limiti, "Detection of signals in MC-CDMA using a novel iterative block decision feedback equalizer," *IEEE Access*, vol. 10, pp. 105674–105684, 2022.

[5] M. H. Jwair, T. A. Elwi, M. Alibakhshikenari, and B. S. Virdee, "Intelligent metasurface layer for direct antenna amplitude modulation scheme," *IEEE Access*, vol. 11, pp. 77506–77517, 2023.

[6] W. Kim and M. F. Iskander, "A new coplanar waveguide continuous transverse stub (CPW-CTS) antenna for wireless communications," *IEEE Antennas Wireless Propag. Lett.*, vol. 4, pp. 172–174, 2005.

[7] A. I. Imran, T. A. Elwi, and A. J. Salim, "On the distortionless of ubw wearable Hilbert-shaped metamaterial antenna for low energy applications," *Prog. Electromagn. Res. M*, vol. 101, pp. 219–239, 2021.

[8] W. Dorothy and R. Joos, *The PIN Diode Circuit Designers*. Watertown, MA, USA: Handbook, 1998.

[9] S. Zahra, L. Ma, W. Wang, J. Li, D. Chen, Y. Liu, Y. Zhou, N. Li, Y. Huang, and G. Wen, "Electromagnetic metasurfaces and reconfigurable metasurfaces: A review," *Frontiers Phys.*, vol. 8, pp. 1–16, Jan. 2021.

[10] T. Bai and R. W. Heath Jr., "Coverage and rate analysis for millimeter-wave cellular networks," *IEEE Trans. Wireless Commun.*, vol. 14, no. 2, pp. 1100–1114, Feb. 2015.

[11] J.-Y. Lee, S.-H. Kim, and J.-H. Jang, "Reduction of mutual coupling in planar multiple antenna by using 1-D EBG and SRR structures," *IEEE Trans. Antennas Propag.*, vol. 63, no. 9, pp. 4194–4198, Sep. 2015.

[12] A. S. Kamel and A. S. A. Jalal, "Novel reconfigurable monopole-based matching circuitry design for 5G and modern wireless communication systems," *Int. J. Commun. Syst.*, vol. 35, no. 14, p. e5252, 2022, doi: 10.1002/dac.5252.
<table><caption>**TABLE 4.** Comparison of antenna array parameters with LDR in the 'ON' and 'OFF' states.</caption><thead><tr><th></th><th>S<sub>11</sub><br>(dB)</th><th>S<sub>21</sub> & S<sub>12</sub><br>(dB)</th></tr></thead><tbody><tr><td>LDR switched OFF @3.5 GHz</td><td>-25</td><td>-38</td></tr><tr><td>LDR switched OFF @4.65 GHz</td><td>-25</td><td>-42</td></tr><tr><td>LDR switched ON @3.5 GHz</td><td>-15</td><td>-42</td></tr><tr><td>LDR switched ON @4.65 GHz</td><td>-30</td><td>-40</td></tr></tbody></table>

<table><caption>**TABLE 5.** Comparison with other MIMO antenna arrays published in literature.</caption><thead><tr><th>Ref.</th><th>Size<br>(λ<sub>o</sub><sup>2</sup>)</th><th>No.<br>radiating<br>elements</th><th>Freq.<br>(GHz)</th><th>Gain<br>(dBi)</th><th>Isolation<br>(dB)</th><th>ECC</th><th>Gap</th></tr></thead><tbody><tr><td>[20]</td><td>2.4×1.8</td><td>8</td><td>5.15/5.95</td><td>2.1</td><td>15</td><td>0.05</td><td>λ/1.9</td></tr><tr><td>[21]</td><td>2.75×1.4</td><td>4</td><td>5.15/5.85</td><td>1.9</td><td>16</td><td>0.06</td><td>λ/2</td></tr><tr><td>[22]</td><td>2.5×1.1</td><td>8</td><td>5.15/5.95</td><td>1.9</td><td>10</td><td>0.09</td><td>λ/2</td></tr><tr><td>[23]</td><td>2.5×1.2</td><td>12</td><td>4.8/5.1</td><td>2.6</td><td>12</td><td>---</td><td>λ/2.1</td></tr><tr><td>[24]</td><td>2.78×1.5</td><td>8</td><td>5.17/5.95</td><td>2.2</td><td>10</td><td>0.11</td><td>λ/2.3</td></tr><tr><td>[25]</td><td>2×2</td><td>4</td><td>3.3/5.8</td><td>1.1</td><td>15</td><td>0.10</td><td>λ/2.1</td></tr><tr><td>[26]</td><td>3×1.3</td><td>2</td><td>5.6/5.67</td><td>12</td><td>30</td><td>0.06</td><td>λ/1.4</td></tr><tr><td>This work</td><td>0.87×0.87</td><td>4</td><td>3.5/4.65</td><td>5.6</td><td>42</td><td>0.01</td><td>λ/8</td></tr></tbody></table>

<figure><img src="image_42.png" /><figcaption>**FIGURE 17.** Problem definition for the SAR analysis. Far-field radiation and SAR values at (a) 3.5 GHz, and (b) 4.65 GHz.</figcaption></figure>

When the LDR switches are in the 'OFF' state the peak value of the SAR is computed to be 0.15 W/kg at 3.5 GHz and 0.21 W/kg at 4.65 GHz. In the 'ON' state the SAR peak value is 1.25 W/kg at 3.5 GHz and 0.94 W/kg at 4.65 GHz. The magnitude of SAR is well below the limit permitted by the FCC in United States, which is 1.6 W/kg averaged over 1 gram of tissue for both head and body exposure. In the European Union, the limit is generally 2.0 W/kg averaged over 10 grams of tissue for head exposure and 2.0 W/kg averaged over 10 grams of tissue for body exposure.

## B. COMPARISON WITH OTHER MIMO ANTENNA ARRAYS

The performance of the proposed antenna array is compared with the other MIMO antenna arrays reported in literature in

Table 5. Compared to the other antenna arrays, the proposed antenna array exhibits better performance in terms of antenna gain, inter-radiating element isolation, and ECC. Moreover, the gap between the radiating elements and the overall array size is significantly smaller. Unlike other antenna arrays, the performance of the proposed array can be reconfigured with LDR switches without the need for DC biasing.

## VI. CONCLUSION

The proposed sub-6 GHz MIMO antenna array with EBG structure is shown to provide high element isolation. The reconfigurability property of the antenna array is also demonstrated using LDR switches. With the proposed EBG structure, the antenna gain of the array is increased by 7.5 dB to +4 dBi at 3.5 GHz and by 14.3 dB to +5.6 dBi at 4.65 GHz. The radiation efficiency at 3.5 GHz and 4.65 GHz are increased to 63% to 61%. This demonstrates the effectiveness of the proposed EBG structure. Moreover, the array exhibits excellent radiation characteristics with EBG. SAR of the antenna array was evaluated on HUGO which is standardized anatomical model of the head in CST Studio Suite. When the LDR switches on the antenna array were either switched 'ON' or 'OFF', the SAR peak value was well below 1.6 W/kg, which is the limit set by the FCC in United States.

## REFERENCES

[1] C. A. Balanis, *Antenna Theory Analysis and Design*, 2013.

[2] I. Ishteyaq and K. Muzaffar, "Multiple input multiple output (MIMO) and fifth generation (5G): An indispensable technology for sub-6 GHz and millimeter wave future generation mobile terminal applications," *Int. J. Microw. Wireless Technol.*, vol. 14, no. 7, pp. 932–948, Sep. 2022.

[3] C. G. Christodoulou, Y. Tawk, S. A. Lane, and S. R. Erwin, "Reconfigurable antennas for wireless and space applications," *Proc. IEEE*, vol. 100, no. 7, pp. 2250–2261, Jun. 2012.

[4] K. Bagadi, K. Sathish, M. Alibakhshikenari, B. S. Virdee, L. Kouhalvandi, K. N. Olan-Nuñez, G. Pau, C. H. See, I. Dayoub, P. Livreri, S. Aïssa, F. Falcone, and E. Limiti, "Detection of signals in MC-CDMA using a novel iterative block decision feedback equalizer," *IEEE Access*, vol. 10, pp. 105674–105684, 2022.

[5] M. H. Jwair, T. A. Elwi, M. Alibakhshikenari, and B. S. Virdee, "Intelligent metasurface layer for direct antenna amplitude modulation scheme," *IEEE Access*, vol. 11, pp. 77506–77517, 2023.

[6] W. Kim and M. F. Iskander, "A new coplanar waveguide continuous transverse stub (CPW-CTS) antenna for wireless communications," *IEEE Antennas Wireless Propag. Lett.*, vol. 4, pp. 172–174, 2005.

[7] A. I. Imran, T. A. Elwi, and A. J. Salim, "On the distortionless of ubw wearable Hilbert-shaped metamaterial antenna for low energy applications," *Prog. Electromagn. Res. M*, vol. 101, pp. 219–239, 2021.

[8] W. Dorothy and R. Joos, *The PIN Diode Circuit Designers*. Watertown, MA, USA: Handbook, 1998.

[9] S. Zahra, L. Ma, W. Wang, J. Li, D. Chen, Y. Liu, Y. Zhou, N. Li, Y. Huang, and G. Wen, "Electromagnetic metasurfaces and reconfigurable metasurfaces: A review," *Frontiers Phys.*, vol. 8, pp. 1–16, Jan. 2021.

[10] T. Bai and R. W. Heath Jr., "Coverage and rate analysis for millimeter-wave cellular networks," *IEEE Trans. Wireless Commun.*, vol. 14, no. 2, pp. 1100–1114, Feb. 2015.

[11] J.-Y. Lee, S.-H. Kim, and J.-H. Jang, "Reduction of mutual coupling in planar multiple antenna by using 1-D EBG and SRR structures," *IEEE Trans. Antennas Propag.*, vol. 63, no. 9, pp. 4194–4198, Sep. 2015.

[12] A. S. Kamel and A. S. A. Jalal, "Novel reconfigurable monopole-based matching circuitry design for 5G and modern wireless communication systems," *Int. J. Commun. Syst.*, vol. 35, no. 14, p. e5252, 2022, doi: 10.1002/dac.5252.
[13] A. R. Azeez, T. A. Elwi, and Z. A. A. Al-Hussain, “Design and analysis of a novel concentric rings based crossed lines single negative metamaterial structure,” *Eng. Sci. Technol., Int. J.*, vol. 20, no. 3, pp. 1140–1146, Jun. 2017.

[14] R. Dilli, “Analysis of 5G wireless systems in FR1 and FR2 frequency bands,” in *Proc. 2nd Int. Conf. Innov. Mech. Ind. Appl. (ICIMIA)*, Mar. 2020, pp. 767–772.

[15] The Homepage of CST Microwave Studio. Accessed: 2024. [Online]. Available: http://www.cst.com/

[16] K. A. Ansal and T. Shanmuganatham, “ACS-fed wide band antenna with L-shaped ground plane for 5.5 GHz WLAN application,” *Prog. Electromagn. Res. Lett.*, vol. 49, pp. 59–64, 2014.

[17] A. K. Abbas and S. Thangavelu, “Compact ACS-fed monopole antenna with CRR defect for triple band application,” *AEU-Int. J. Electron. Commun.*, vol. 127, Dec. 2020, Art. no. 153487.

[18] L. Kang, H. Wang, X. H. Wang, and X. Shi, “Compact ACS-fed monopole antenna with rectangular SRRs for tri-band operation,” *Electron. Lett.*, vol. 50, no. 16, pp. 1112–1114, Jul. 2014.

[19] M. H. Jwair and T. A. Elwi, “Steerable composite right-left-hand-based printed antenna circuitry for 5G applications,” *Microw. Opt. Technol. Lett.*, vol. 65, no. 7, pp. 1–8, 2023.

[20] Y. Li, H. Zou, M. Wang, M. Peng, and G. Yang, “Eight-element MIMO antenna array for 5G/sub-6 GHz indoor micro wireless access points,” in *Proc. Int. Workshop Antenna Technol. (iWAT)*, Mar. 2018, pp. 1–4.

[21] Z. Ren, S. Wu, and A. Zhao, “Triple band MIMO antenna system for 5G mobile terminals,” in *Proc. Int. Workshop Antenna Technol. (iWAT)*, Mar. 2019, pp. 163–165.

[22] C.-Y.-D. Sim, H.-Y. Liu, and C.-J. Huang, “Wideband MIMO antenna array design for future mobile devices operating in the 5G NR frequency bands n77/n78/n79 and LTE band 46,” *IEEE Antennas Wireless Propag. Lett.*, vol. 19, no. 1, pp. 74–78, Jan. 2020.

[23] Y. Li, C.-Y.-D. Sim, Y. Luo, and G. Yang, “12-port 5G massive MIMO antenna array in sub-6 GHz mobile handset for LTE bands 42/43/46 applications,” *IEEE Access*, vol. 6, pp. 344–354, 2018.

[24] J. Guo, L. Cui, C. Li, and B. Sun, “Side-edge frame printed eight-port dual-band antenna array for 5G smartphone applications,” *IEEE Trans. Antennas Propag.*, vol. 66, no. 12, pp. 7412–7417, Dec. 2018.

[25] W. M. Abdulkawi, W. A. Malik, S. U. Rehman, A. Aziz, A. F. A. Sheta, and M. A. Alkanhal, “Design of a compact dual-band MIMO antenna system with high-diversity gain performance in both frequency bands,” *Micromachines*, vol. 12, no. 4, p. 383, Apr. 2021.

[26] J. Khan, S. Ullah, F. A. Tahir, F. Tubbal, and R. Raad, “A sub-6 GHz MIMO antenna array for 5G wireless terminals,” *Electronics*, vol. 10, no. 24, p. 3062, Dec. 2021.

[27] W. Yu, S. Yang, C.-L. Tang, and D. Tu, “Accurate simulation of the radiation performance of a mobile slide phone in a hand-head position,” *IEEE Antennas Propag. Mag.*, vol. 52, no. 2, pp. 168–177, Apr. 2010.

[28] J. Krogerus, C. Icheln, and P. Vainikainen, “Effect of human body on 3-D radiation pattern and efficiency of mobile handsets,” in *Proc. IEEE Instrum. Meas. Technol. Conf.*, 2005, pp. 271–276.

[29] J. Krogerus, C. Icheln, and P. Vainikainen, “Experimental investigation of antenna performance of GSM phones in body-worn and browsing use positions,” in *Proc. Eur. Conf. Wireless Technol.*, Sep. 2006, pp. 330–333.

<figure><img src="image_43.png" /></figure>

**TAHA A. ELWI** received the B.Sc. degree from the Electrical Engineering Department, Al-Nakhain University, Baghdad, Iraq, in 2003, the M.Sc. (master's) degree from the Laser and Optoelectronics Engineering Department, Al-Nakhain University, in 2005, and the Ph.D. degree in system engineering and science, in December 2011. From April 2005 to August 2007, he was with Huawei Technologies Company, Baghdad. In January 2008, he joined the University of

Arkansas at Little Rock. He is currently the Head of the International Applied and Theoretical Research Center (IATRC), Baghdad. He is the supervisor of many funded projects and Ph.D. theses with more than 250 published papers and holds ten patents. His research interests include wearable and implantable antennas for biomedical wireless systems, smart antennas, WiFi deployment, electromagnetic wave scattering by complex objects, design, modeling, and testing of metamaterial structures for microwave applications,

design and analysis of microstrip antennas for mobile radio systems, precipitation effects on terrestrial and satellite frequency re-use communication systems, effects of the complex media on electromagnetic propagation, GPS, pattern recognition, signal and image processing, machine learning, deep learning, game theory, and medical image analysis-based artificial intelligence algorithms and classifications. His research is conducted to consider wireless sensor networks based on microwave terminals and laser optoelectronic devices. The nano-scale structures in the entire electromagnetic spectrum are a part of his research interest. Also, his work is extended to realize advancements in reconfigurable intelligent surfaces and control the channel performance. Nevertheless, the evaluation of modern physics phenomena in wireless communication networks, including cognitive radio networks and squint effects is currently part of his research. He serves as an editor in many international journals and publishers, such as MDPI, IEEE, Springer, and Elsevier. Also, he has been a member of the Iraqi Scientific Research Consultant, since 2016. He is leading three collaborations around the world regarding biomedical applications using microwave technology. He is considered one of Stanford University's top 2% scientists, in 2022.

<figure><img src="image_44.png" /></figure>

**FATMA TAHER** (Senior Member, IEEE) received the Ph.D. degree from the Khalifa University of Science, Technology and Research, United Arab Emirates, in 2014. She is currently the Assistant Dean of the College of Technological Innovation, Zayed University, Dubai, United Arab Emirates. She has published more than 40 papers in international journals and conferences. Her research interests include signal and image processing, pattern recognition, deep learning, machine learning,

artificial intelligence, and medical image analysis, especially in detecting cancerous cells, kidney transplants, and autism. In addition to that, her research includes watermarking, remote sensing, and satellite images. She served as a member of the steering, organizing, and technical program committees for many international conferences. Her current publication and research interests include image classification, medical image processing, deep learning (artificial intelligence), diseases, image segmentation, neural nets, CAD, internet, the Internet of Things, Markov processes, antenna radiation patterns, artificial intelligence, biomedical MRI, broadband antennas, cancer, cardiology, computer crime, computer network security, computerized tomography, convolutional neural nets, data compression, data structures, diagnostic radiography, discrete cosine transforms, and distributed processing.

<figure><img src="image_45.png" /></figure>

**BAL S. VIRDEE** (Senior Member, IEEE) received the B.Sc. degree in engineering from the University of Leeds, U.K., and the Ph.D. degree from the University of London, U.K. Since graduation, he has worked in the industry for various high-tech companies, including Philips, U.K., as a Research and Development Engineer, and Teledyne Defence and Space, U.K., as a Future Products Developer of RF/microwave communications. He has taught in several academic institutions in the U.K. He is

currently a Senior Professor of communications technology and the Director of the Center for Communications Technology, School of Computing and Digital Media, London Metropolitan University. He has published numerous research articles. His research, in collaboration with industry and academia, is in communications systems. He is a Chartered Engineer and a fellow of the IET. He is the Chair and an Executive Member of the IET's Technical and Professional Network Committee on RF/Microwave Technology.
[13] A. R. Azeez, T. A. Elwi, and Z. A. A. Al-Hussain, "Design and analysis of a novel concentric rings based crossed lines single negative metamaterial structure," *Eng. Sci. Technol., Int. J.*, vol. 20, no. 3, pp. 1140–1146, Jun. 2017.

[14] R. Dilli, "Analysis of 5G wireless systems in FR1 and FR2 frequency bands," in *Proc. 2nd Int. Conf. Innov. Mech. Ind. Appl. (ICIMIA)*, Mar. 2020, pp. 767–772.

[15] The Homepage of CST Microwave Studio. Accessed: 2024. [Online]. Available: http://www.cst.com/

[16] K. A. Ansal and T. Shanmuganatham, "ACS-fed wide band antenna with L-shaped ground plane for 5.5 GHz WLAN application," *Prog. Electromagn. Res. Lett.*, vol. 49, pp. 59–64, 2014.

[17] A. K. Abbas and S. Thangavelu, "Compact ACS-fed monopole antenna with CRR defect for triple band application," *AEU-Int. J. Electron. Commun.*, vol. 127, Dec. 2020, Art. no. 153487.

[18] L. Kang, H. Wang, X. H. Wang, and X. Shi, "Compact ACS-fed monopole antenna with rectangular SRRs for tri-band operation," *Electron. Lett.*, vol. 50, no. 16, pp. 1112–1114, Jul. 2014.

[19] M. H. Jwair and T. A. Elwi, "Steerable composite right-left-hand-based printed antenna circuitry for 5G applications," *Microw. Opt. Technol. Lett.*, vol. 65, no. 7, pp. 1–8, 2023.

[20] Y. Li, H. Zou, M. Wang, M. Peng, and G. Yang, "Eight-element MIMO antenna array for 5G/sub-6 GHz indoor micro wireless access points," in *Proc. Int. Workshop Antenna Technol. (iWAT)*, Mar. 2018, pp. 1–4.

[21] Z. Ren, S. Wu, and A. Zhao, "Triple band MIMO antenna system for 5G mobile terminals," in *Proc. Int. Workshop Antenna Technol. (iWAT)*, Mar. 2019, pp. 163–165.

[22] C.-Y.-D. Sim, H.-Y. Liu, and C.-J. Huang, "Wideband MIMO antenna array design for future mobile devices operating in the 5G NR frequency bands n77/n78/n79 and LTE band 46," *IEEE Antennas Wireless Propag. Lett.*, vol. 19, no. 1, pp. 74–78, Jan. 2020.

[23] Y. Li, C.-Y.-D. Sim, Y. Luo, and G. Yang, "12-port 5G massive MIMO antenna array in sub-6 GHz mobile handset for LTE bands 42/43/46 applications," *IEEE Access*, vol. 6, pp. 344–354, 2018.

[24] J. Guo, L. Cui, C. Li, and B. Sun, "Side-edge frame printed eight-port dual-band antenna array for 5G smartphone applications," *IEEE Trans. Antennas Propag.*, vol. 66, no. 12, pp. 7412–7417, Dec. 2018.

[25] W. M. Abdulkawi, W. A. Malik, S. U. Rehman, A. Aziz, A. F. A. Sheta, and M. A. Alkanhal, "Design of a compact dual-band MIMO antenna system with high-diversity gain performance in both frequency bands," *Micromachines*, vol. 12, no. 4, p. 383, Apr. 2021.

[26] J. Khan, S. Ullah, F. A. Tahir, F. Tubbal, and R. Raad, "A sub-6 GHz MIMO antenna array for 5G wireless terminals," *Electronics*, vol. 10, no. 24, p. 3062, Dec. 2021.

[27] W. Yu, S. Yang, C.-L. Tang, and D. Tu, "Accurate simulation of the radiation performance of a mobile slide phone in a hand-head position," *IEEE Antennas Propag. Mag.*, vol. 52, no. 2, pp. 168–177, Apr. 2010.

[28] J. Krogerus, C. Icheln, and P. Vainikainen, "Effect of human body on 3-D radiation pattern and efficiency of mobile handsets," in *Proc. IEEE Instrum. Meas. Technol. Conf.*, 2005, pp. 271–276.

[29] J. Krogerus, C. Icheln, and P. Vainikainen, "Experimental investigation of antenna performance of GSM phones in body-worn and browsing use positions," in *Proc. Eur. Conf. Wireless Technol.*, Sep. 2006, pp. 330–333.

<figure><img src="image_43.png" /></figure>

**TAHA A. ELWI** received the B.Sc. degree from the Electrical Engineering Department, Al-Nakhair University, Baghdad, Iraq, in 2003, the M.Sc. (master's) degree from the Laser and Optoelectronics Engineering Department, Al-Nakhair University, in 2005, and the Ph.D. degree in system engineering and science, in December 2011. From April 2005 to August 2007, he was with Huawei Technologies Company, Baghdad. In January 2008, he joined the University of

Arkansas at Little Rock. He is currently the Head of the International Applied and Theoretical Research Center (IATRC), Baghdad. He is the supervisor of many funded projects and Ph.D. theses with more than 250 published papers and holds ten patents. His research interests include wearable and implantable antennas for biomedical wireless systems, smart antennas, WiFi deployment, electromagnetic wave scattering by complex objects, design, modeling, and testing of metamaterial structures for microwave applications,

design and analysis of microstrip antennas for mobile radio systems, precipitation effects on terrestrial and satellite frequency re-use communication systems, effects of the complex media on electromagnetic propagation, GPS, pattern recognition, signal and image processing, machine learning, deep learning, game theory, and medical image analysis-based artificial intelligence algorithms and classifications. His research is conducted to consider wireless sensor networks based on microwave terminals and laser optoelectronic devices. The nano-scale structures in the entire electromagnetic spectrum are a part of his research interest. Also, his work is extended to realize advancements in reconfigurable intelligent surfaces and control the channel performance. Nevertheless, the evaluation of modern physics phenomena in wireless communication networks, including cognitive radio networks and squint effects is currently part of his research. He serves as an editor in many international journals and publishers, such as MDPI, IEEE, Springer, and Elsevier. Also, he has been a member of the Iraqi Scientific Research Consultant, since 2016. He is leading three collaborations around the world regarding biomedical applications using microwave technology. He is considered one of Stanford University's top 2% scientists, in 2022.

<figure><img src="image_44.png" /></figure>

**FATMA TAHER** (Senior Member, IEEE) received the Ph.D. degree from the Khalifa University of Science, Technology and Research, United Arab Emirates, in 2014. She is currently the Assistant Dean of the College of Technological Innovation, Zayed University, Dubai, United Arab Emirates. She has published more than 40 papers in international journals and conferences. Her research interests include signal and image processing, pattern recognition, deep learning, machine learning,

artificial intelligence, and medical image analysis, especially in detecting cancerous cells, kidney transplants, and autism. In addition to that, her research includes watermarking, remote sensing, and satellite images. She served as a member of the steering, organizing, and technical program committees for many international conferences. Her current publication and research interests include image classification, medical image processing, deep learning (artificial intelligence), diseases, image segmentation, neural nets, CAD, internet, the Internet of Things, Markov processes, antenna radiation patterns, artificial intelligence, biomedical MRI, broadband antennas, cancer, cardiology, computer crime, computer network security, computerized tomography, convolutional neural nets, data compression, data structures, diagnostic radiography, discrete cosine transforms, and distributed processing.

<figure><img src="image_45.png" /></figure>

**BAL S. VIRDEE** (Senior Member, IEEE) received the B.Sc. degree in engineering from the University of Leeds, U.K., and the Ph.D. degree from the University of London, U.K. Since graduation, he has worked in the industry for various high-tech companies, including Philips, U.K., as a Research and Development Engineer, and Teledyne Defence and Space, U.K., as a Future Products Developer of RF/microwave communications. He has taught in several academic institutions in the U.K. He is

currently a Senior Professor of communications technology and the Director of the Center for Communications Technology, School of Computing and Digital Media, London Metropolitan University. He has published numerous research articles. His research, in collaboration with industry and academia, is in communications systems. He is a Chartered Engineer and a fellow of the IET. He is the Chair and an Executive Member of the IET's Technical and Professional Network Committee on RF/Microwave Technology.
<figure><img src="image_46.png" /></figure>

**MOHAMMAD ALIBAKHSHIKENARI** (Member, IEEE) was born in Mazandaran, Iran, in February 1988. He received the Ph.D. degree with a European Label in electronics engineering from the University of Rome "Tor Vergata," Italy, in February 2020. From May 2018 to December 2018, he was a Ph.D. Visiting Researcher with Chalmers University of Technology, Gothenburg, Sweden. His training during this Ph.D. research visit included a research stage with Swedish Company Gap Waves AB, Gothenburg. Since July 2021, he has been with the Department of Signal Theory and Communications, Universidad Carlos III de Madrid (uc3m), Spain, as a Principal Investigator of the CONEX (CONnecting EXcellence)-Plus Talent Training Program and Marie Skłodowska-Curie Actions. He was also a Lecturer with the Electromagnetic Fields and Electromagnetic Laboratory, Department of Signal Theory and Communications, from 2021 to 2022. He received the "Teaching Excellent Acknowledgement" Certificate for the course of electromagnetic fields from the Vice-Rector of Studies of uc3m. From December 2022 to May 2023, he spent three industrial and academic research visits, such as SARAS Technology Ltd. Company, Leeds, U.K.; Edinburgh Napier University, Edinburgh, Scotland, U.K.; and the University of Bradford, Bradford, England, U.K., which were defined by CONEX-Plus Talent Training Program and Marie Skłodowska-Curie Actions as his secondment research visit plans. His research interests include electromagnetic systems, antennas and wave-propagations, metamaterials and metasurfaces, sensors, synthetic aperture radars (SAR), 5G and beyond wireless communications, multiple input multiple output (MIMO) systems, RFID tag antennas, substrate integrated waveguides (SIWs), impedance matching circuits, microwave components, millimeter-waves and terahertz integrated circuits, gap waveguide technology, beamforming matrix, and reconfigurable intelligent surfaces (RIS), which led to achieve more than 5800 citations and H-index above 48 reported by Scopus, Google Scholar, and ResearchGate. He was a recipient of the three-year Principal Investigator Research grant funded by Universidad Carlos III de Madrid and European Union's Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie Grant started, in July 2021, the two years Postdoctoral Research Grant funded by the University of Rome "Tor Vergata" started, in November 2019, the three years Ph.D. Scholarship funded by the University of Rome "Tor Vergata" started, in November 2016, and the two Young Engineer Awards of the 47th and 48th European Microwave Conference were held in Nuremberg, Germany, in 2017, and Madrid, Spain, in 2018, respectively. In April 2020, his research article titled "High-Gain Metasurface in Polyimide On-Chip Antenna Based on CRLH-TL for Sub Terahertz Integrated Circuits" published in Scientific Reports was awarded as the Best Month Paper at the University of Bradford, West Yorkshire, England. He is serving as an Associate Editor for *Radio Science and IET Journal of Engineering*. He also acts as a referee in several highly reputed journals and international conferences.

<figure><img src="image_47.png" /></figure>

**IGNACIO J. GARCIA ZUAZOLA** received the FPII degree in industrial electronics from the School of Chemistry and Electronics, Indautxu, Spain, in 1995, the Higher National Diploma degree in telecommunications engineering from the University of Middlesex, London, U.K., in 2000, the B.Eng. degree in telecommunications engineering from the Queen Mary University of London, in 2003, the Ph.D. degree in electronics from the University of Kent, Canterbury, U.K., in 2010, and the e-MBA degree in business from Cardiff Metropolitan University, Cardiff, U.K., in 2016. He was with Babcok and Wilcox, Bilbao, Spain, in 1993; Iberdrola, Santurce, Spain, in 1995; Telefonica, Bilbao, in 1997; Thyssen Elevators, Bilbao, in 1998; and Cell Communications, Bilbao, in 2000; and engaged in an SME in electrical wiring at Gartzola, Bilbao, in 1996. He was formerly employed as a Research Associate with the University of Kent in 2004 and 2008; a Research Engineer with the University of Wales, Swansea, U.K., in 2006; a Senior Research Fellow with the University of Deusto, Bilbao, in 2011; a Visiting Senior Research Fellow with the University of Leeds, Leeds, U.K., in 2011; and a Research Associate with Loughborough University, Loughborough, U.K., in 2014. He has been

a Representative of Spain with the London School of Commerce, U.K., since 2015; and a Research Collaborator with the University of Deusto, Bizkaia, Spain, since 2015. In 2022, he joined London Metropolitan University as a Senior Lecturer. His research interests include business development on one hand and single-band and multiband miniature antennas, and the use of electromagnetic bandgap structures and frequency-selective surfaces. He was a recipient of various awards in electrical wiring, pneumatic and hydraulic systems, and robotics.

<figure><img src="image_48.png" /></figure>

**ASTRIT KRASNIQI** has an extensive experience in industry and academia. He is a qualified Cisco Certified Academy Instructor for CCNA and CCNP Courses internationally. His research interests include communications systems and cyber security.

<figure><img src="image_49.png" /></figure>

**AMNA SHIBIB KAMEL** was born in Baghdad, Iraq, in 1993. She received the B.Sc. degree (Hons.) from the Department of Communication Engineering, Al-Mammon University College, Baghdad, in 2015, and the M.Sc. degree from the Department of Information and Communication Engineering, Nairain University, Baghdad, in 2022. Since 2022, she has been an Assistant Lecturer in electronics and communication engineering with Al-Turath University. Her main research interests include deep learning, antennas, and microwave devices.

<figure><img src="image_50.png" /></figure>

**NURHAN TÜRKER TOKAN** received the B.Sc. degree in electronics and communications engineering from Kocaeli University, in 2002, and the M.Sc. and Ph.D. degrees in communication engineering from Yildiz Technical University (YTU), Istanbul, Turkey, in 2004 and 2009, respectively. From May 2003 to May 2009, she was a Research Assistant with the Electromagnetic Fields and Microwave Technique Section, Electronics and Communication Engineering Department, YTU. From May 2009 and April 2015, she was an Assistant Professor, and from April 2015 and August 2021, she was an Associate Professor with the Electronics and Communications Engineering Department, YTU, where she has been a Professor, Since August 2020. From October 2011 to October 2012, she was a Postdoctoral Researcher with the Department of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Delft, The Netherlands. From October 2012 to May 2013, she was a Postdoctoral Fellow supported by European Science Foundation with the Institute of Electronics and Telecommunications (IETR), University of Rennes 1, Rennes, France. She is the author or coauthor of more than 50 papers published in peer-reviewed international journals and conference proceedings. Her current research interests include the analysis and design of antennas with an emphasis on dielectric lens antennas and wideband antennas, microwave circuits, and intelligent systems.

**SALAHUDDIN KHAN**, photograph and biography not available at the time of publication.
<figure><img src="image_46.png" /></figure>

**MOHAMMAD ALIBAKHSHIKENARI** (Member, IEEE) was born in Mazandaran, Iran, in February 1988. He received the Ph.D. degree with a European Label in electronics engineering from the University of Rome “Tor Vergata,” Italy, in February 2020. From May 2018 to December 2018, he was a Ph.D. Visiting Researcher with Chalmers University of Technology, Gothenburg, Sweden. His training during this Ph.D. research visit included a research stage with Swedish Company Gap Waves AB, Gothenburg. Since July 2021, he has been with the Department of Signal Theory and Communications, Universidad Carlos III de Madrid (uc3m), Spain, as a Principal Investigator of the CONEX (CONnecting EXcellence)-Plus Talent Training Program and Marie Skłodowska-Curie Actions. He was also a Lecturer with the Electromagnetic Fields and Electromagnetic Laboratory, Department of Signal Theory and Communications, from 2021 to 2022. He received the “Teaching Excellent Acknowledgement” Certificate for the course of electromagnetic fields from the Vice-Rector of Studies of uc3m. From December 2022 to May 2023, he spent three industrial and academic research visits, such as SARAS Technology Ltd. Company, Leeds, U.K.; Edinburgh Napier University, Edinburgh, Scotland, U.K.; and the University of Bradford, Bradford, England, U.K., which were defined by CONEX-Plus Talent Training Program and Marie Skłodowska-Curie Actions as his secondment research visit plans. His research interests include electromagnetic systems, antennas and wave-propagations, metamaterials and metasurfaces, sensors, synthetic aperture radars (SAR), 5G and beyond wireless communications, multiple input multiple output (MIMO) systems, RFID tag antennas, substrate integrated waveguides (SIWs), impedance matching circuits, microwave components, millimeter-waves and terahertz integrated circuits, gap waveguide technology, beamforming matrix, and reconfigurable intelligent surfaces (RIS), which led to achieve more than 5800 citations and H-index above 48 reported by Scopus, Google Scholar, and ResearchGate. He was a recipient of the three-year Principal Investigator Research grant funded by Universidad Carlos III de Madrid and European Union's Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie Grant started, in July 2021, the two years Postdoctoral Research Grant funded by the University of Rome “Tor Vergata” started, in November 2019, the three years Ph.D. Scholarship funded by the University of Rome “Tor Vergata” started, in November 2016, and the two Young Engineer Awards of the 47th and 48th European Microwave Conference were held in Nuremberg, Germany, in 2017, and Madrid, Spain, in 2018, respectively. In April 2020, his research article titled “High-Gain Metasurface in Polyimide On-Chip Antenna Based on CRLH-TL for Sub Terahertz Integrated Circuits” published in Scientific Reports was awarded as the Best Month Paper at the University of Bradford, West Yorkshire, England. He is serving as an Associate Editor for *Radio Science and IET Journal of Engineering*. He also acts as a referee in several highly reputed journals and international conferences.

<figure><img src="image_47.png" /></figure>

**IGNACIO J. GARCIA ZUAZOLA** received the FPII degree in industrial electronics from the School of Chemistry and Electronics, Indautxu, Spain, in 1995, the Higher National Diploma degree in telecommunications engineering from the University of Middlesex, London, U.K., in 2000, the B.Eng. degree in telecommunications engineering from the Queen Mary University of London, in 2003, the Ph.D. degree in electronics from the University of Kent, Canterbury, U.K., in 2010, and the e-MBA degree in business from Cardiff Metropolitan University, Cardiff, U.K., in 2016. He was with Babcok and Wilcox, Bilbao, Spain, in 1993; Iberdrola, Santurce, Spain, in 1995; Telefonica, Bilbao, in 1997; Thyssen Elevators, Bilbao, in 1998; and Cell Communications, Bilbao, in 2000; and engaged in an SME in electrical wiring at Gartzola, Bilbao, in 1996. He was formerly employed as a Research Associate with the University of Kent in 2004 and 2008; a Research Engineer with the University of Wales, Swansea, U.K., in 2006; a Senior Research Fellow with the University of Deusto, Bilbao, in 2011; a Visiting Senior Research Fellow with the University of Leeds, Leeds, U.K., in 2011; and a Research Associate with Loughborough University, Loughborough, U.K., in 2014. He has been

a Representative of Spain with the London School of Commerce, U.K., since 2015; and a Research Collaborator with the University of Deusto, Bizkaia, Spain, since 2015. In 2022, he joined London Metropolitan University as a Senior Lecturer. His research interests include business development on one hand and single-band and multiband miniature antennas, and the use of electromagnetic bandgap structures and frequency-selective surfaces. He was a recipient of various awards in electrical wiring, pneumatic and hydraulic systems, and robotics.

<figure><img src="image_48.png" /></figure>

**ASTRIT KRASNIQI** has an extensive experience in industry and academia. He is a qualified Cisco Certified Academy Instructor for CCNA and CCNP Courses internationally. His research interests include communications systems and cyber security.

<figure><img src="image_49.png" /></figure>

**AMNA SHIBIB KAMEL** was born in Baghdad, Iraq, in 1993. She received the B.Sc. degree (Hons.) from the Department of Communication Engineering, Al-Mammon University College, Baghdad, in 2015, and the M.Sc. degree from the Department of Information and Communication Engineering, Nairain University, Baghdad, in 2022. Since 2022, she has been an Assistant Lecturer in electronics and communication engineering with Al-Turath University. Her main research interests include deep learning, antennas, and microwave devices.

<figure><img src="image_50.png" /></figure>

**NURHAN TÜRKER TOKAN** received the B.Sc. degree in electronics and communications engineering from Kocaeli University, in 2002, and the M.Sc. and Ph.D. degrees in communication engineering from Yildiz Technical University (YTU), Istanbul, Turkey, in 2004 and 2009, respectively. From May 2003 to May 2009, she was a Research Assistant with the Electromagnetic Fields and Microwave Technique Section, Electronics and Communication Engineering Department, YTU. From May 2009 and April 2015, she was an Assistant Professor, and from April 2015 and August 2021, she was an Associate Professor with the Electronics and Communications Engineering Department, YTU, where she has been a Professor, Since August 2020. From October 2011 to October 2012, she was a Postdoctoral Researcher with the Department of Electrical Engineering, Mathematics and Computer Science, Delft University of Technology, Delft, The Netherlands. From October 2012 to May 2013, she was a Postdoctoral Fellow supported by European Science Foundation with the Institute of Electronics and Telecommunications (IETR), University of Rennes 1, Rennes, France. She is the author or coauthor of more than 50 papers published in peer-reviewed international journals and conference proceedings. Her current research interests include the analysis and design of antennas with an emphasis on dielectric lens antennas and wideband antennas, microwave circuits, and intelligent systems.

**SALAHUDDIN KHAN**, photograph and biography not available at the time of publication.
<figure><img src="image_51.png" /></figure>

**NASER OJAROUDI PARCHIN** (Senior Member, IEEE) received the Ph.D. degree in electrical engineering from the University of Bradford, U.K. He was a Postdoctoral Research Assistant with the Faculty of Engineering and Informatics, University of Bradford. He is currently an Assistant Professor (a Lecturer) with Edinburgh Napier University, U.K. He was a Research Fellow with the SATNEX V Project, funded by European Space Agency. In 2016, he was a Visiting Researcher

with Ankara University, Turkey. From 2014 to 2018, he was with the APMS Section, Aalborg University, Denmark. From 2018 to 2020, he was a Marie Curie Research Fellow with the H2020-ITN-SECRET Project, funded by the EU Commission, targeting 5G mobile small cells. He has over 12 years of research experience in antennas and microwave engineering. He is the author and coauthor of several books/book chapters and more than 300 technical journals and conference papers. His research interests include phased arrays, MIMO systems, smartphone antennas, SAR/user-impact, full-duplex diversity, 5G antennas, implementable and biomedical sensors, RFID tag antennas, millimeter-wave and terahertz components, fractal structures, metamaterials/metasurfaces, PCB realization, Fabry resonators, EBG/FSS-inspired radiators, microwave filters, reconfigurable structures, and wireless propagation. He is a member of the Institute of Marie Curie Alumni Association (MCAA) and European Association on Antennas and Propagation (EurAAP). He was a recipient and co-recipient of various awards and grants for research publications, such as the Research Development Fund, in 2019, the MDPI Travel Award, in 2020/2021, the Best Paper Awards from the URSI Symposium, in 2019, the 5G Summit, in 2019, the U.K. URSI Festival, in 2020, the IMDC, in 2021, and the ITC-Egypt, in 2022. He is a research grant reviewer of the Dutch Science Council (NWO). He is also an Active Reviewer in various high-ranking journals and publishers, such as *IEEE TRANSACTIONS*, *IEEE ACCESS/Letters*, IET, Wiley, Springer, Elsevier, and MDPI. He is also appointed as a guest editor and a topic board for several MDPI journals. He was included in the World's Top Scientists list in 2016, 2020, 2021, and 2022. His papers have more than 6300 citations with an H-index of 44, as reported by Google Scholar. His score is higher than 95% of all RG members' scores.

<figure><img src="image_52.png" /></figure>

**PATRIZIA LIVRERI** (Senior Member, IEEE) received the “Laurea” degree (Hons.) in electronics engineering and the Ph.D. degree in electronics and communications engineering from the University of Palermo, Italy, in 1986 and 1992, respectively. She is currently a Professor with the Department of Engineering, University of Palermo, and a Visiting Professor with the San Diego State University. From 1993 to 1994, she was a Researcher with CNR. Since 1995, she has

been serving as the Scientific Director for the Microwave Instruments and Measurements Laboratory, Engineering Department, University of Palermo. In 2020, she also joined the CNIT National Laboratory for Radar and Surveillance Systems RaSS, Pisa. Her research interests include microwave and millimeter vacuum high power (TWT, Klystron) and solid-state power amplifiers for radar applications; high power microwave source (virtual cathode oscillator, magnetically insulated transmission line oscillator); microwave and optical antennas, radar, and microwave quantum radar. She is the Principal Investigator of the Microwave Quantum Radar Project, funded by the Ministry of Defense, in 2021. She is a supervisor of many funded projects and the author of more than 200 published articles.

<figure><img src="image_53.png" /></figure>

**IYAD DAYOUB** (Senior Member, IEEE) received the B.Eng. degree in telecommunications and electronics in Syria, in 1993, the M.A.Sc. degree in electrical engineering from the National Polytechnic Institute of Lorraine (INPL), and the Ph.D. degree from the University of Valenciennes and the Institute of Electronics, Microelectronics and Nanotechnology (IEMN), in 2001. He worked as a System Engineer with Siemens, Middle East; and a Researcher with Alcatel Business Systems,

Alcatel, Colombes, Paris. He was an Adjunct Professor with Concordia University, Montreal, from 2010 to 2014. He is currently a Professor of communications engineering with IEMN, Université Polytechnique Hauts-de-France (UPHF), and INSA H-d-F, where his current research activities are focused on wireless communications, high-speed communications, cognitive radio, and hybrid radio-optic technologies. He was a member of the National Council of Universities (CNU), France, from 2007 to 2014, in the area of electrical engineering, electronics, photonics, and systems. He is a member of several international conference advisory committees, technical program committees, and organization committees, such as VTC, GLOBECOM, ICC, PIMRC, and WWC.

<figure><img src="image_54.png" /></figure>

**GIOVANNI PAU** (Senior Member, IEEE) received the bachelor's degree in telematic engineering from the University of Catania, Italy, and the master's (cum laude) and Ph.D. degrees in telematic engineering from the Kore University of Enna, Italy. He is currently an Associate Professor with the Faculty of Engineering and Architecture, Kore University of Enna. He is the author/coauthor of more than 80 refereed papers published in journals and conference proceedings. His research interests

include wireless sensor networks, fuzzy logic controllers, intelligent transportation systems, the Internet of Things, smart homes, and network security. He is a member of the IEEE (Italy Section) and has been involved in several international conferences as the session co-chair and a technical program committee member. He serves/served as a leading guest editor for the special issues of several international journals. He is an Editorial Board Member and an Associate Editor of several journals, such as *IEEE ACCESS*, *Wireless Networks* (Springer), *EURASIP Journal on Wireless Communications and Networking* (Springer), *Wireless Communications and Mobile Computing* (Hindawi), and *Sensors* (MDPI), and *Future Internet* (MDPI).

<figure><img src="image_55.png" /></figure>

**SONIA AÏSSA** (Fellow, IEEE) received the Ph.D. degree in electrical and computer engineering from McGill University, Montreal, QC, Canada, in 1998. Since then, she has been with the Institut National de la Recherche Scientifique (INRS), Université du Québec, Montreal, QC, Canada, where she is currently a Full Professor. From 1996 to 1997, she was a Researcher with the Department of Electronics and Communications, Kyoto University, and the Wireless Systems Lab-

oratories of NTT, Japan. From 1998 to 2000, she was a Research Associate with INRS-EMT. From 2000 to 2002, she was an Assistant Professor. She was a Principal Investigator in the major program of personal and mobile communications of Canadian Institute for Telecommunications Research, leading research in radio resource management for wireless networks. From 2004 to 2007, she was an Adjunct Professor with Concordia University, Canada. She was a Visiting Invited Professor with Kyoto University, Japan, in 2006, and Universiti Sains Malaysia, in 2015. Her research interests include the modeling, design, and performance evaluation of wireless communication systems and networks, and wireless power technologies. She is a fellow of Canadian Academy of Engineering. Awards to her credit include the NSERC University Faculty Award, in 1999; the Quebec Government FRQNT Strategic Faculty Fellowship, from 2001 to 2006; the INRS-EMT Performance Award multiple times since 2004, for outstanding achievements in research, teaching, and service; and the Technical Community Service Award from the FRQNT Centre for Advanced Systems and Technologies in Communications, in 2007. She was a co-recipient of five IEEE Best
<figure><img src="image_51.png" /></figure>

**NASER OJAROUDI PARCHIN** (Senior Member, IEEE) received the Ph.D. degree in electrical engineering from the University of Bradford, U.K. He was a Postdoctoral Research Assistant with the Faculty of Engineering and Informatics, University of Bradford. He is currently an Assistant Professor (a Lecturer) with Edinburgh Napier University, U.K. He was a Research Fellow with the SATNEX V Project, funded by European Space Agency. In 2016, he was a Visiting Researcher

with Ankara University, Turkey. From 2014 to 2018, he was with the APMS Section, Aalborg University, Denmark. From 2018 to 2020, he was a Marie Curie Research Fellow with the H2020-ITN-SECRET Project, funded by the EU Commission, targeting 5G mobile small cells. He has over 12 years of research experience in antennas and microwave engineering. He is the author and coauthor of several books/book chapters and more than 300 technical journals and conference papers. His research interests include phased arrays, MIMO systems, smartphone antennas, SAR/user-impact, full-duplex diversity, 5G antennas, implementable and biomedical sensors, RFID tag antennas, millimeter-wave and terahertz components, fractal structures, metamaterials/metasurfaces, PCB realization, Fabry resonators, EBG/FSS-inspired radiators, microwave filters, reconfigurable structures, and wireless propagation. He is a member of the Institute of Marie Curie Alumni Association (MCAA) and European Association on Antennas and Propagation (EurAAP). He was a recipient and co-recipient of various awards and grants for research publications, such as the Research Development Fund, in 2019, the MDPI Travel Award, in 2020/2021, the Best Paper Awards from the URSI Symposium, in 2019, the 5G Summit, in 2019, the U.K. URSI Festival, in 2020, the IMDC, in 2021, and the ITC-Egypt, in 2022. He is a research grant reviewer of the Dutch Science Council (NWO). He is also an Active Reviewer in various high-ranking journals and publishers, such as *IEEE TRANSACTIONS*, *IEEE ACCESS/Letters*, IET, Wiley, Springer, Elsevier, and MDPI. He is also appointed as a guest editor and a topic board for several MDPI journals. He was included in the World's Top Scientists list in 2016, 2020, 2021, and 2022. His papers have more than 6300 citations with an H-index of 44, as reported by Google Scholar. His score is higher than 95% of all RG members' scores.

<figure><img src="image_52.png" /></figure>

**PATRIZIA LIVRERI** (Senior Member, IEEE) received the “Laurea” degree (Hons.) in electronics engineering and the Ph.D. degree in electronics and communications engineering from the University of Palermo, Italy, in 1986 and 1992, respectively. She is currently a Professor with the Department of Engineering, University of Palermo, and a Visiting Professor with the San Diego State University. From 1993 to 1994, she was a Researcher with CNR. Since 1995, she has

been serving as the Scientific Director for the Microwave Instruments and Measurements Laboratory, Engineering Department, University of Palermo. In 2020, she also joined the CNIT National Laboratory for Radar and Surveillance Systems RaSS, Pisa. Her research interests include microwave and millimeter vacuum high power (TWT, Klystron) and solid-state power amplifiers for radar applications; high power microwave source (virtual cathode oscillator, magnetically insulated transmission line oscillator); microwave and optical antennas, radar, and microwave quantum radar. She is the Principal Investigator of the Microwave Quantum Radar Project, funded by the Ministry of Defense, in 2021. She is a supervisor of many funded projects and the author of more than 200 published articles.

<figure><img src="image_53.png" /></figure>

**IYAD DAYOUB** (Senior Member, IEEE) received the B.Eng. degree in telecommunications and electronics in Syria, in 1993, the M.A.Sc. degree in electrical engineering from the National Polytechnic Institute of Lorraine (INPL), and the Ph.D. degree from the University of Valenciennes and the Institute of Electronics, Microelectronics and Nanotechnology (IEMN), in 2001. He worked as a System Engineer with Siemens, Middle East; and a Researcher with Alcatel Business Systems,

Alcatel, Colombes, Paris. He was an Adjunct Professor with Concordia University, Montreal, from 2010 to 2014. He is currently a Professor of communications engineering with IEMN, Université Polytechnique Hauts-de-France (UPHF), and INSA H-d-F, where his current research activities are focused on wireless communications, high-speed communications, cognitive radio, and hybrid radio-optic technologies. He was a member of the National Council of Universities (CNU), France, from 2007 to 2014, in the area of electrical engineering, electronics, photonics, and systems. He is a member of several international conference advisory committees, technical program committees, and organization committees, such as VTC, GLOBECOM, ICC, PIMRC, and WWC.

<figure><img src="image_54.png" /></figure>

**GIOVANNI PAU** (Senior Member, IEEE) received the bachelor's degree in telematic engineering from the University of Catania, Italy, and the master's (cum laude) and Ph.D. degrees in telematic engineering from the Kore University of Enna, Italy. He is currently an Associate Professor with the Faculty of Engineering and Architecture, Kore University of Enna. He is the author/coauthor of more than 80 refereed papers published in journals and conference proceedings. His research interests

include wireless sensor networks, fuzzy logic controllers, intelligent transportation systems, the Internet of Things, smart homes, and network security. He is a member of the IEEE (Italy Section) and has been involved in several international conferences as the session co-chair and a technical program committee member. He serves/served as a leading guest editor for the special issues of several international journals. He is an Editorial Board Member and an Associate Editor of several journals, such as *IEEE ACCESS*, *Wireless Networks* (Springer), *EURASIP Journal on Wireless Communications and Networking* (Springer), *Wireless Communications and Mobile Computing* (Hindawi), and *Sensors* (MDPI), and *Future Internet* (MDPI).

<figure><img src="image_55.png" /></figure>

**SONIA AÏSSA** (Fellow, IEEE) received the Ph.D. degree in electrical and computer engineering from McGill University, Montreal, QC, Canada, in 1998. Since then, she has been with the Institut National de la Recherche Scientifique (INRS), Université du Quebec, Montreal, QC, Canada, where she is currently a Full Professor. From 1996 to 1997, she was a Researcher with the Department of Electronics and Communications, Kyoto University, and the Wireless Systems Lab-

oratories of NTT, Japan. From 1998 to 2000, she was a Research Associate with INRS-EMT. From 2000 to 2002, she was an Assistant Professor. She was a Principal Investigator in the major program of personal and mobile communications of Canadian Institute for Telecommunications Research, leading research in radio resource management for wireless networks. From 2004 to 2007, she was an Adjunct Professor with Concordia University, Canada. She was a Visiting Invited Professor with Kyoto University, Japan, in 2006, and Universiti Sains Malaysia, in 2015. Her research interests include the modeling, design, and performance evaluation of wireless communication systems and networks, and wireless power technologies. She is a fellow of Canadian Academy of Engineering. Awards to her credit include the NSERC University Faculty Award, in 1999; the Quebec Government FRQNT Strategic Faculty Fellowship, from 2001 to 2006; the INRS-EMT Performance Award multiple times since 2004, for outstanding achievements in research, teaching, and service; and the Technical Community Service Award from the FRQNT Centre for Advanced Systems and Technologies in Communications, in 2007. She was a co-recipient of five IEEE Best
Paper Awards and the 2012 IEICE Best Paper Award; and recipient of the NSERC Discovery Accelerator Supplement Award. She was the Founding Chair of the IEEE Women in Engineering Affinity Group in Montreal, from 2004 to 2007; acted as the TPC Symposium Chair or Co-Chair at IEEE ICC 2006, 2009, 2011, and 2012; the Program Co-Chair at IEEE WCNC 2007; the TPC Co-Chair of IEEE VTC-Spring 2013; the TPC Symposia Chair of IEEE Globecom 2014; and the TPC Vice-Chair of IEEE Globecom 2018. She also serves as the TPC Chair of IEEE ICC 2021. Her main editorial activities include an Editor of *IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS*, from 2004 to 2012; an Associate Editor and a Technical Editor for *IEEE Communications Magazine*, from 2004 to 2015; a Technical Editor for *IEEE Wireless Communications Magazine*, from 2006 to 2010; and an Associate Editor for *Security and Communication Networks* (Wiley), from 2007 to 2012. She currently serves as an Area Editor for *IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS*. She served as Distinguished Lecturer of the IEEE Communications Society and a member of its Board of Governors, from 2013 to 2016 and from 2014 to 2016, respectively.

<figure><img src="image_56.png" /></figure>

**ERNESTO LIMITI** (Senior Member, IEEE) has been a Full Professor of Electronics with the Engineering Faculty, University of Roma Tor Vergata, since 2002, after being a research and teaching assistant, since 1991, and an Associate Professor, since 1998. He represents the University of Roma Tor Vergata in the governing body of the Microwave Engineering Center for Space Applications (MECSA), an inter-university center among several Italian Universities. He has been elected to

represent the Industrial Engineering sector in the Academic Senate of the University, from 2007 to 2010 and from 2010 to 2013. He is the President of the Consortium "Advanced Research and Engineering for Space," ARES, formed between the University and two companies. Further, he is the President of the Laurea and Laurea Magistrale degrees in Electronic Engineering of the University of Roma "Tor Vergata." His research activity is focused on three main lines, all of them belonging to the microwave and millimeter-wave electronics research area. The first one is related to the characterization and modeling of active and passive microwave and millimeter-wave devices. Regarding active devices, the research line is oriented to small-signal, noise, and large-signal modeling. Regarding passive devices, equivalent-circuit models have been developed for interacting discontinuities in microstrip, for typical MMIC passive components (MIM capacitors), and for waveguide/coplanar waveguide transitions analysis and design. For active devices, new methodologies have been developed for the noise characterization and the subsequent modeling, and equivalent-circuit modeling strategies have been implemented both for small and large-signal operating regimes for GaAs, GaN, SiC, Si, and InP MESFET/HEMT devices. The second line is related to design methodologies and characterization methods for low-noise circuits. The focus is on cryogenic amplifiers and devices. Collaborations are currently ongoing with the major radio astronomy institutes all around Europe within the frame of FP6 and FP7 programs (RadioNet). Finally, the third line is in the analysis methods for nonlinear microwave circuits. In this line, novel analysis methods (Spectral Balance) are developed, together with

the stability analysis of the solutions making use of traditional (harmonic balance) approaches. The above research lines have produced more than 250 publications in refereed international journals and presentations at international conferences. He acts as a referee of international journals of the microwave and millimeter wave electronics sector and is on the steering committee of international conferences and workshops. He is actively involved in research activities with many research groups, both European and Italian. He is in tight collaborations with high-tech Italian (Selex-SI, Thales Alenia Space, Rheinmetall, Elettronica S.p.A., and Space Engineering) and foreign (OMMIC, Siemens, and UMS) companies. He contributed, as a researcher and/or as the unit responsible, to several National (PRIN MIUR, Madess CNR, and Agenzia Spaziale Italiana) and international (ESPRIT COSMIC, Manpower, Edge, Special Action MEPI, ESA, EUROPA, Korrigan, RadioNet FP6, and FP7) projects. Regarding teaching activities, he teaches, over his institutional duties in the frame of the Corso di Laurea Magistrale in Ingegneria Elettronica, "Elettronica per lo Spazio" within the Master Course in Sistemi Avanzati di Comunicazione e Navigazione Satellitare. He is a member of the committee of the Ph.D. program in Telecommunications and Microelectronics with the University of Roma Tor Vergata, tutoring an average of four Ph.D. candidates per year.

<figure><img src="image_57.png" /></figure>

**MOHAMED FATHY ABO SREE** received the Master of Science (M.Sc.) degree from Arab Academy for Science, Technology, and Maritime Transport (AASTMT), Cairo, Egypt, in 2013, and the Ph.D. degree in electrical engineering from Ain Shams University, Egypt, in 2019, thereby solidifying and expanding his expertise. He currently holds the position of an Associate Professor with the Department of Electronics and Communication Engineering, AASTMT, a role he has been

fulfilled since 2019. Within this role, he is dedicated to advancing academic excellence in his field. Throughout his academic and professional journey, he has consistently pursued and achieved significant milestones. Actively engaging with the academic community, he participates in the peer review process for prestigious journals such as IEEE Access and the PIER online journal. This involvement underscores his unwavering commitment to upholding the quality and integrity of scientific contributions within his specialized field. An eminent aspect of his professional profile lies in his prolific publication record. He has authored and co-authored 76 research articles, all indexed in the Science Citation Index (SCI), with an additional seven articles indexed in SCOPUS. This underscores the international recognition garnered by his work. His academic impact is further underscored by an impressive H-index of 10, signifying that he has authored at least 10 papers, each cited a minimum of ten times. The substantial citation count of 399 reflects the widespread recognition and influence of his contributions within the scholarly community. Notably, the i10 index, representing publications with at least ten citations, aligns seamlessly with his H-index, highlighting the consistency and depth of his scholarly contributions. His commendable H-index and substantial citation count collectively affirm his significant and enduring impact on the academic field.

...
Paper Awards and the 2012 IEICE Best Paper Award; and recipient of the NSERC Discovery Accelerator Supplement Award. She was the Founding Chair of the IEEE Women in Engineering Affinity Group in Montreal, from 2004 to 2007; acted as the TPC Symposium Chair or Co-Chair at IEEE ICC 2006, 2009, 2011, and 2012; the Program Co-Chair at IEEE WCNC 2007; the TPC Co-Chair of IEEE VTC-Spring 2013; the TPC Symposia Chair of IEEE Globecom 2014; and the TPC Vice-Chair of IEEE Globecom 2018. She also serves as the TPC Chair of IEEE ICC 2021. Her main editorial activities include an Editor of *IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS*, from 2004 to 2012; an Associate Editor and a Technical Editor for *IEEE Communications Magazine*, from 2004 to 2015; a Technical Editor for *IEEE Wireless Communications Magazine*, from 2006 to 2010; and an Associate Editor for *Security and Communication Networks* (Wiley), from 2007 to 2012. She currently serves as an Area Editor for *IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS*. She served as Distinguished Lecturer of the IEEE Communications Society and a member of its Board of Governors, from 2013 to 2016 and from 2014 to 2016, respectively.

<figure><img src="image_56.png" /></figure>

**ERNESTO LIMITI** (Senior Member, IEEE) has been a Full Professor of Electronics with the Engineering Faculty, University of Roma Tor Vergata, since 2002, after being a research and teaching assistant, since 1991, and an Associate Professor, since 1998. He represents the University of Roma Tor Vergata in the governing body of the Microwave Engineering Center for Space Applications (MECSA), an inter-university center among several Italian Universities. He has been elected to

represent the Industrial Engineering sector in the Academic Senate of the University, from 2007 to 2010 and from 2010 to 2013. He is the President of the Consortium "Advanced Research and Engineering for Space," ARES, formed between the University and two companies. Further, he is the President of the Laurea and Laurea Magistrale degrees in Electronic Engineering of the University of Roma "Tor Vergata." His research activity is focused on three main lines, all of them belonging to the microwave and millimeter-wave electronics research area. The first one is related to the characterization and modeling of active and passive microwave and millimeter-wave devices. Regarding active devices, the research line is oriented to small-signal, noise, and large-signal modeling. Regarding passive devices, equivalent-circuit models have been developed for interacting discontinuities in microstrip, for typical MMIC passive components (MIM capacitors), and for waveguide/coplanar waveguide transitions analysis and design. For active devices, new methodologies have been developed for the noise characterization and the subsequent modeling, and equivalent-circuit modeling strategies have been implemented both for small and large-signal operating regimes for GaAs, GaN, SiC, Si, and InP MESFET/HEMT devices. The second line is related to design methodologies and characterization methods for low-noise circuits. The focus is on cryogenic amplifiers and devices. Collaborations are currently ongoing with the major radio astronomy institutes all around Europe within the frame of FP6 and FP7 programs (RadioNet). Finally, the third line is in the analysis methods for nonlinear microwave circuits. In this line, novel analysis methods (Spectral Balance) are developed, together with

the stability analysis of the solutions making use of traditional (harmonic balance) approaches. The above research lines have produced more than 250 publications in refereed international journals and presentations at international conferences. He acts as a referee of international journals of the microwave and millimeter wave electronics sector and is on the steering committee of international conferences and workshops. He is actively involved in research activities with many research groups, both European and Italian. He is in tight collaborations with high-tech Italian (Selex-SI, Thales Alenia Space, Rheinmetall, Elettronica S.p.A., and Space Engineering) and foreign (OMMIC, Siemens, and UMS) companies. He contributed, as a researcher and/or as the unit responsible, to several National (PRIN MIUR, Madess CNR, and Agenzia Spaziale Italiana) and international (ESPRIT COSMIC, Manpower, Edge, Special Action MEPI, ESA, EUROPA, Korrigan, RadioNet FP6, and FP7) projects. Regarding teaching activities, he teaches, over his institutional duties in the frame of the Corso di Laurea Magistrale in Ingegneria Elettronica, "Elettronica per lo Spazio" within the Master Course in Sistemi Avanzati di Comunicazione e Navigazione Satellitare. He is a member of the committee of the Ph.D. program in Telecommunications and Microelectronics with the University of Roma Tor Vergata, tutoring an average of four Ph.D. candidates per year.

<figure><img src="image_57.png" /></figure>

**MOHAMED FATHY ABO SREE** received the Master of Science (M.Sc.) degree from Arab Academy for Science, Technology, and Maritime Transport (AASTMT), Cairo, Egypt, in 2013, and the Ph.D. degree in electrical engineering from Ain Shams University, Egypt, in 2019, thereby solidifying and expanding his expertise. He currently holds the position of an Associate Professor with the Department of Electronics and Communication Engineering, AASTMT, a role he has been

fulfilled since 2019. Within this role, he is dedicated to advancing academic excellence in his field. Throughout his academic and professional journey, he has consistently pursued and achieved significant milestones. Actively engaging with the academic community, he participates in the peer review process for prestigious journals such as IEEE Access and the PIER online journal. This involvement underscores his unwavering commitment to upholding the quality and integrity of scientific contributions within his specialized field. An eminent aspect of his professional profile lies in his prolific publication record. He has authored and co-authored 76 research articles, all indexed in the Science Citation Index (SCI), with an additional seven articles indexed in SCOPUS. This underscores the international recognition garnered by his work. His academic impact is further underscored by an impressive H-index of 10, signifying that he has authored at least 10 papers, each cited a minimum of ten times. The substantial citation count of 399 reflects the widespread recognition and influence of his contributions within the scholarly community. Notably, the i10 index, representing publications with at least ten citations, aligns seamlessly with his H-index, highlighting the consistency and depth of his scholarly contributions. His commendable H-index and substantial citation count collectively affirm his significant and enduring impact on the academic field.

...