# Broadband 3-D Shared Aperture High Isolation Nine-Element Antenna Array for On-Demand Millimeter-Wave 5G Applications

Mohammad Alibakhshikenari, Bal Virdee, Valeria Vadalà, Mariana Dalarsson, María Elena de Cos Gómez, Abdullah Alharbi, Shah Nawaz Burokur, Sonia Aïssa, Iyad Dayoub, Francisco Falcone, et al.

► To cite this version:

Mohammad Alibakhshikenari, Bal Virdee, Valeria Vadalà, Mariana Dalarsson, María Elena de Cos Gómez, et al. Broadband 3-D Shared Aperture High Isolation Nine-Element Antenna Array for On-Demand Millimeter-Wave 5G Applications. Optik, 2022, 267, pp.169708. 10.1016/j.ijleo.2022.169708. hal-03739680

HAL Id: hal-03739680

https://hal.science/hal-03739680

Submitted on 12 Jun 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_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
# Broadband 3-D Shared Aperture High Isolation Nine-Element Antenna Array for On-Demand Millimeter-Wave 5G Applications

Mohammad Alibakhshikenari, Bal Virdee, Valeria Vadalà, Mariana Dalarsson, María Elena de Cos Gómez, Abdullah Alharbi, Shah Nawaz Burokur, Sonia Aïssa, Iyad Dayoub, Francisco Falcone, et al.

► To cite this version:

Mohammad Alibakhshikenari, Bal Virdee, Valeria Vadalà, Mariana Dalarsson, María Elena de Cos Gómez, et al. Broadband 3-D Shared Aperture High Isolation Nine-Element Antenna Array for On-Demand Millimeter-Wave 5G Applications. Optik, 2022, 267, pp.169708. 10.1016/j.ijleo.2022.169708. hal-03739680

HAL Id: hal-03739680

https://hal.science/hal-03739680v1

Submitted on 12 Jun 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_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
<figure><img src="image_2.png" /></figure>

<figure><img src="image_3.png" /></figure>

Check for
updates

# Broadband 3-D shared aperture high isolation nine-element antenna array for on-demand millimeter-wave 5G applications

Mohammad Alibakhshikenari<sup>a, *</sup>, Bal S. Virdee<sup>b</sup>, Valeria Vadalà<sup>c</sup>, Mariana Dalarsson<sup>d</sup>, María Elena de Cos Gómez<sup>e</sup>, Abdullah G. Alharbi<sup>f</sup>, Shah Nawaz Burokur<sup>g</sup>, Sonia Aïssa<sup>h</sup>, Iyad Dayoub<sup>i,j</sup>, Francisco Falcone<sup>k,l</sup>, Ernesto Limiti<sup>m</sup>

ARTICLE INFO

Keywords:

Array antennas
Metasurface (MTS)
Isolation wall
5G
Shared aperture
Three dimensional (3-D)

ABSTRACT

The paper presents the results of a novel 3-D shared aperture 3 × 3 matrix antenna-array for 26 GHz band 5 G wireless networks. Radiation elements constituting the array are hexagonal-shaped patches that are elevated above the common dielectric substrate by 3.35 mm and excited through a metallic rod of 0.4 mm diameter. The rod protrudes through the substrate of 0.8 mm thickness. It is shown that by isolating each radiating element in the array with a wall suppresses unwanted electromagnetic (EM) wave interactions, resulting in improvement in the antenna's impedance matching and radiation characteristics. Moreover, the results show that by embedding hexagonal-shaped slots in the patches improve the antenna's gain and radiation efficiency performance. The subwavelength length slots in the patches essentially transform the radiating elements to exhibit metasurface characteristics when the array is illuminated by EM-waves. The proposed array structure has an average gain and radiation efficiency of 20 dBi and 93%, respectively, across 24.0–28.4 GHz. The isolation between its radiation elements is greater than 22 dB. Compared to the unslotted array the improvement in isolation between radiating elements is greater than 11

E-mail addresses: mohammad.alibakhshikenari@uc3m.es (M. Alibakhshikenari), b.virdee@londonmet.ac.uk (B.S. Virdee), valeria.vadala@unimib.it (V. Vadalà), mardal@kth.se (M. Dalarsson), medecos@uniovi.es (M.E. de Cos Gómez), a.g.alharbi@ieee.org (A.G. Alharbi), sburokur@parisnanterre.fr (S.N. Burokur), sonia.aissa@inrs.ca (S. Aïssa), iyad.dayoub@uphf.fr (I. Dayoub), francisco.falcone@unavarra.es (F. Falcone), limiti@ing.uniroma2.it (E. Limiti).

<footnote><sup>a</sup> Department of Signal Theory and Communications, Universidad Carlos III de Madrid, 28911 Leganés, Madrid, Spain</footnote>

<footnote><sup>b</sup> Center for Communications Technology, London Metropolitan University, UK</footnote>

<footnote><sup>c</sup> Department of Physics, University of Milano-Bicocca, 20126, Milan, Italy</footnote>

<footnote><sup>d</sup> School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, SE 100-44 Stockholm, Sweden</footnote>

<footnote><sup>e</sup> TSC. Electrical Engineering Department, University of Oviedo, 33203 Gijón, Spain</footnote>

<footnote><sup>f</sup> Department of Electrical Engineering, Faculty of Engineering, Jouf University, Sakaka 42421, Saudi Arabia</footnote>

<footnote><sup>g</sup> LEMA, UPL, Université Paris-Nanterre, F92410, Ville d'Avray, France</footnote>

<footnote><sup>h</sup> Institut National de la Recherche Scientifique (INRS), Montreal, QC, H5A 1K6, Canada</footnote>

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

<footnote><sup>j</sup> INSA Hauts de France, F-59313 Valenciennes, France</footnote>

<footnote><sup>k</sup> Department of Electric, Electronic and Communication Engineering and the Institute of Smart Cities, Public University of Navarre, 31006 Pamplona, Spain</footnote>

<footnote><sup>l</sup> Tecnologico de Monterrey, School of Engineering and Sciences</footnote>

<footnote><sup>m</sup> Electronic Engineering Department, University of Rome "Tor Vergata", Via del Politecnico 1, 00133 Rome, Italy</footnote>

<footnote>* Corresponding author.</footnote>
<figure><img src="image_2.png" /></figure>

ELSEVIER

Contents lists available at ScienceDirect

Optik

journal homepage: www.elsevier.com/locate/ijleo

<figure><img src="image_3.png" /></figure>

<figure><img src="image_4.png" /></figure>

Check for
updates

# Broadband 3-D shared aperture high isolation nine-element antenna array for on-demand millimeter-wave 5G applications

Mohammad Alibakhshikenari<sup>a, *</sup>, Bal S. Virdee<sup>b</sup>, Valeria Vadalà<sup>c</sup>, Mariana Dalarsson<sup>d</sup>, María Elena de Cos Gómez<sup>e</sup>, Abdullah G. Alharbi<sup>f</sup>, Shah Nawaz Burokur<sup>g</sup>, Sonia Aïssa<sup>h</sup>, Iyad Dayoub<sup>i,j</sup>, Francisco Falcone<sup>k,l</sup>, Ernesto Limiti<sup>m</sup>

ARTICLE INFO

Keywords:

Array antennas
Metasurface (MTS)
Isolation wall
5G
Shared aperture
Three dimensional (3-D)

ABSTRACT

The paper presents the results of a novel 3-D shared aperture 3 × 3 matrix antenna-array for 26 GHz band 5 G wireless networks. Radiation elements constituting the array are hexagonal-shaped patches that are elevated above the common dielectric substrate by 3.35 mm and excited through a metallic rod of 0.4 mm diameter. The rod protrudes through the substrate of 0.8 mm thickness. It is shown that by isolating each radiating element in the array with a wall suppresses unwanted electromagnetic (EM) wave interactions, resulting in improvement in the antenna's impedance matching and radiation characteristics. Moreover, the results show that by embedding hexagonal-shaped slots in the patches improve the antenna's gain and radiation efficiency performance. The subwavelength length slots in the patches essentially transform the radiating elements to exhibit metasurface characteristics when the array is illuminated by EM-waves. The proposed array structure has an average gain and radiation efficiency of 20 dBi and 93%, respectively, across 24.0–28.4 GHz. The isolation between its radiation elements is greater than 22 dB. Compared to the unslotted array the improvement in isolation between radiating elements is greater than 11

E-mail addresses: mohammad.alibakhshikenari@uc3m.es (M. Alibakhshikenari), b.virdee@londonmet.ac.uk (B.S. Virdee), valeria.vadala@unimib.it (V. Vadalà), mardal@kth.se (M. Dalarsson), medecos@uniovi.es (M.E. de Cos Gómez), a.g.alharbi@ieee.org (A.G. Alharbi), sburokur@parisnanterre.fr (S.N. Burokur), sonia.aissa@inrs.ca (S. Aïssa), iyad.dayoub@uphf.fr (I. Dayoub), francisco.falcone@unavarra.es (F. Falcone), limiti@ing.uniroma2.it (E. Limiti).

https://doi.org/10.1016/j.ijleo.2022.169708

Received 22 September 2021; Received in revised form 29 April 2022; Accepted 19 July 2022

Available online 22 July 2022

0030-4026/© 2022 The Authors. Published by Elsevier GmbH. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

<footnote><sup>a</sup> Department of Signal Theory and Communications, Universidad Carlos III de Madrid, 28911 Leganés, Madrid, Spain</footnote>

<footnote><sup>b</sup> Center for Communications Technology, London Metropolitan University, UK</footnote>

<footnote><sup>c</sup> Department of Physics, University of Milano-Bicocca, 20126, Milan, Italy</footnote>

<footnote><sup>d</sup> School of Electrical Engineering and Computer Science, KTH Royal Institute of Technology, SE 100-44 Stockholm, Sweden</footnote>

<footnote><sup>e</sup> TSC. Electrical Engineering Department, University of Oviedo, 33203 Gijón, Spain</footnote>

<footnote><sup>f</sup> Department of Electrical Engineering, Faculty of Engineering, Jouf University, Sakaka 42421, Saudi Arabia</footnote>

<footnote><sup>g</sup> LEME, UPL, Université Paris-Nanterre, F92410, Ville d'Avray, France</footnote>

<footnote><sup>h</sup> Institut National de la Recherche Scientifique (INRS), Montreal, QC, H5A 1K6, Canada</footnote>

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

<footnote><sup>j</sup> INSA Hauts de France, F-59313 Valenciennes, France</footnote>

<footnote><sup>k</sup> Department of Electric, Electronic and Communication Engineering and the Institute of Smart Cities, Public University of Navarre, 31006 Pamplona, Spain</footnote>

<footnote><sup>l</sup> Tecnologico de Monterrey, School of Engineering and Sciences</footnote>

<footnote><sup>m</sup> Electronic Engineering Department, University of Rome "Tor Vergata", Via del Politecnico 1, 00133 Rome, Italy</footnote>

<footnote>* Corresponding author.</footnote>
dB, and the gain and efficiency are better than 10.5 dBi, and 25%, respectively. The compact array has a fractional bandwidth of 16% and a form factor of 20 × 20 × 3.35 mm³.

# 1. Introduction

Worldwide deployment of 5 G wireless communication systems is currently underway [1]. Unlike the previous generations of cellular systems, 5 G offers benefits of faster internet connectivity and capability to link with thousands of devices [2]. This technology makes the realization of Internet of Things (IoT) or Internet of Everything (IoE) possible as well as the creation of new ‘smart’ services capable of providing information in real-time. The frequency bands used in the initial phase of 5 G deployment are between 700 MHz and 3.8 GHz. This frequency band were originally used for previous generations of mobile technology. The demand for bandwidth is expected to grow with greater usage of 5 G. This demand can only be met by using the millimeter-wave 5 G spectrum at 26 GHz. The large data transmission capacity [3] of the millimeter-band is associated with a high loss resulting from propagation, atmospheric loss, pathloss, dielectric-loss, radiation-loss, and metallic loss in transmission-lines [4,5], To compensate for such loss, research is now focused on antenna array technologies at the millimeter-wave band [6–9].

In this paper, a novel 3-D shared aperture 3 × 3 antenna array concept is proposed for 5 G millimeter-wave applications operating over 24–28.4 GHz. The antenna array consists of hexagonal-shaped patches that are perched above a common substrate and excited using metallic rods through the substrate. Individual antennas are decoupled from each other with an isolation wall to prevent unwanted mutual coupling that can degrade the overall far-field performance of the antenna. To enhance the gain and radiation efficiency of the antenna the patches are made to exhibit metasurface characteristics. This is achieved by loading the patches with hexagonal-shaped concentric slots of decreasing diameters. The feeding structure of the proposed array makes it amenable to either single aperture or shared aperture antenna applications as it covers a relatively wide bandwidth. This is achieved by grouping together individual antennas in the array to form sub arrays that are used to cover a specific portion of the total bandwidth for different applications on time/frequency shared basis [10,11].

# 2. 3D shared aperture nine-element antenna array

Geometry of the proposed 3-D shared aperture nine element antenna array is shown in Fig. 1. The array consists of hexagonal-shaped patches that are constructed on the base dielectric substrate (Rogers RT5880) with a thickness of 0.2 mm, dielectric constant of 2.2, and tanδ of 0.0009. The radiating patches are elevated above the dielectric substrate by 3.35 mm using a metallic rod of 0.4 mm diameter. The base substrate of 0.8 mm thickness has a ground-plane. The metallic rods protrude through the base substrate and are insulated from the ground-plane metallization layer. Each antenna is exited through the metallic rods. By raising the antenna above the substrate effectively reduces surface current interactions between adjacent antennas which can drastically undermine the antenna’s characteristics. The structural parameters of the array are listed in Table 1. The overall size of the proposed basic antenna array is 20 × 20 × 3.35 mm³.

Theoretical modeling of such an array is provided in [12]. To validate the design of the proposed antenna array it was constructed and analyzed using two very different 3-D electromagnetic solvers, namely, CST Microwave Studio and Ansoft HFSS. The numerical EM-solver by Ansoft HFSS is based on frequency-domain finite-element method (FEM), and CST Microwave Studio is based on a

<figure><img src="image_4.png" /><figcaption>Fig. 1. 3-D shared aperture nine element 3 × 3 array antennas, (a) isometric top-view, and (b) side view.</figcaption></figure>
dB, and the gain and efficiency are better than 10.5 dBi, and 25%, respectively. The compact array has a fractional bandwidth of 16% and a form factor of 20 × 20 × 3.35 mm³.

# 1. Introduction

Worldwide deployment of 5 G wireless communication systems is currently underway [1]. Unlike the previous generations of cellular systems, 5 G offers benefits of faster internet connectivity and capability to link with thousands of devices [2]. This technology makes the realization of Internet of Things (IoT) or Internet of Everything (IoE) possible as well as the creation of new ‘smart’ services capable of providing information in real-time. The frequency bands used in the initial phase of 5 G deployment are between 700 MHz and 3.8 GHz. This frequency band were originally used for previous generations of mobile technology. The demand for bandwidth is expected to grow with greater usage of 5 G. This demand can only be met by using the millimeter-wave 5 G spectrum at 26 GHz. The large data transmission capacity [3] of the millimeter-band is associated with a high loss resulting from propagation, atmospheric loss, pathloss, dielectric-loss, radiation-loss, and metallic loss in transmission-lines [4,5], To compensate for such loss, research is now focused on antenna array technologies at the millimeter-wave band [6–9].

In this paper, a novel 3-D shared aperture 3 × 3 antenna array concept is proposed for 5 G millimeter-wave applications operating over 24–28.4 GHz. The antenna array consists of hexagonal-shaped patches that are perched above a common substrate and excited using metallic rods through the substrate. Individual antennas are decoupled from each other with an isolation wall to prevent unwanted mutual coupling that can degrade the overall far-field performance of the antenna. To enhance the gain and radiation efficiency of the antenna the patches are made to exhibit metasurface characteristics. This is achieved by loading the patches with hexagonal-shaped concentric slots of decreasing diameters. The feeding structure of the proposed array makes it amenable to either single aperture or shared aperture antenna applications as it covers a relatively wide bandwidth. This is achieved by grouping together individual antennas in the array to form sub arrays that are used to cover a specific portion of the total bandwidth for different applications on time/frequency shared basis [10,11].

# 2. 3D shared aperture nine-element antenna array

Geometry of the proposed 3-D shared aperture nine element antenna array is shown in Fig. 1. The array consists of hexagonal-shaped patches that are constructed on the base dielectric substrate (Rogers RT5880) with a thickness of 0.2 mm, dielectric constant of 2.2, and tanδ of 0.0009. The radiating patches are elevated above the dielectric substrate by 3.35 mm using a metallic rod of 0.4 mm diameter. The base substrate of 0.8 mm thickness has a ground-plane. The metallic rods protrude through the base substrate and are insulated from the ground-plane metallization layer. Each antenna is exited through the metallic rods. By raising the antenna above the substrate effectively reduces surface current interactions between adjacent antennas which can drastically undermine the antenna’s characteristics. The structural parameters of the array are listed in Table 1. The overall size of the proposed basic antenna array is 20 × 20 × 3.35 mm³.

Theoretical modeling of such an array is provided in [12]. To validate the design of the proposed antenna array it was constructed and analyzed using two very different 3-D electromagnetic solvers, namely, CST Microwave Studio and Ansoft HFSS. The numerical EM-solver by Ansoft HFSS is based on frequency-domain finite-element method (FEM), and CST Microwave Studio is based on a

<figure><img src="image_5.png" /><figcaption>Fig. 1. 3-D shared aperture nine element 3 × 3 array antennas, (a) isometric top-view, and (b) side view.</figcaption></figure>
<table><caption>**Table 1**

Geometrical Parameters of the Array (units in millimeters).</caption><thead><tr><th>Length</th><th>Width</th><th>La</th><th>Wa</th><th>Lw</th><th>Ww</th><th>Lp</th></tr></thead><tbody><tr><td>20</td><td>20</td><td>4</td><td>4</td><td>5</td><td>5</td><td>1.75</td></tr><tr><td>dhole</td><td>drod</td><td>Hrod</td><td>Hw</td><td>hs<sub>1</sub></td><td>hs<sub>2</sub></td><td>d<sub>1</sub></td></tr><tr><td>0.5</td><td>0.2</td><td>3.35</td><td>2</td><td>0.8</td><td>0.2</td><td>3</td></tr><tr><td>d<sub>2</sub></td><td>s</td><td>g</td><td>Ws</td><td>Wml</td><td>form factor</td><td></td></tr><tr><td>2</td><td>7</td><td>0.25</td><td>0.08</td><td>0.2</td><td>20 × 20 × 3.35</td><td></td></tr></tbody></table>

Note: *Ws* and *Wml* represent the width of the slots and meandered-lines, respectively. Some parameters are annotated in Fig. 4 & 5.

<figure><img src="image_5.png" /><figcaption>**Fig. 2.** Active S-parameter response of the proposed antenna array, (a) reflection-coefficient ($S_{11}$), (b) transmission-coefficient between antennas #1&#2 ($S_{12}$), (c) transmission-coefficient between antennas #1&#3 ($S_{13}$), (d) transmission-coefficient between antennas #1&#4 ($S_{14}$), (e) transmission-coefficient between antennas #1&#5 ($S_{15}$), (f) transmission-coefficient between antennas #1&#6 ($S_{16}$), (g) transmission-coefficient between antennas #1&#7 ($S_{17}$), (h) transmission-coefficient between antennas #1&#8 ($S_{18}$), and (i) transmission-coefficient between antennas #1&#9 ($S_{19}$).</figcaption></figure>

time-domain finite integration technique (FIT) method.

The active S-parameters in Fig. 2(a) shows that the proposed basic antenna array exhibits an impedance bandwidth of 700 MHz and operates across 26.5–27.2 GHz, which corresponds to a the fractional bandwidth (FBW) of 2.6%. The transmission-coefficient response between the radiation elements is shown in Fig. 2(b)-(i). These results show that the average isolation between the patches #2 to #9
<table><caption>**Table 1**

Geometrical Parameters of the Array (units in millimeters).</caption><thead><tr><th>Length</th><th>Width</th><th>La</th><th>Wa</th><th>Lw</th><th>Ww</th><th>Lp</th></tr></thead><tbody><tr><td>20</td><td>20</td><td>4</td><td>4</td><td>5</td><td>5</td><td>1.75</td></tr><tr><td>dhole</td><td>drod</td><td>Hrod</td><td>Hw</td><td>hs<sub>1</sub></td><td>hs<sub>2</sub></td><td>d<sub>1</sub></td></tr><tr><td>0.5</td><td>0.2</td><td>3.35</td><td>2</td><td>0.8</td><td>0.2</td><td>3</td></tr><tr><td>d<sub>2</sub></td><td>s</td><td>g</td><td>Ws</td><td>Wml</td><td>form factor</td><td></td></tr><tr><td>2</td><td>7</td><td>0.25</td><td>0.08</td><td>0.2</td><td>20 × 20 × 3.35</td><td></td></tr></tbody></table>

Note: *Ws* and *Wml* represent the width of the slots and meandered-lines, respectively. Some parameters are annotated in Fig. 4 & 5.

<figure><img src="image_6.png" /><figcaption>**Fig. 2.** Active S-parameter response of the proposed antenna array, (a) reflection-coefficient (S<sub>11</sub>), (b) transmission-coefficient between antennas #1&#2 (S<sub>12</sub>), (c) transmission-coefficient between antennas #1&#3 (S<sub>13</sub>), (d) transmission-coefficient between antennas #1&#4 (S<sub>14</sub>), (e) transmission-coefficient between antennas #1&#5 (S<sub>15</sub>), (f) transmission-coefficient between antennas #1&#6 (S<sub>16</sub>), (g) transmission-coefficient between antennas #1&#7 (S<sub>17</sub>), (h) transmission-coefficient between antennas #1&#8 (S<sub>18</sub>), and (i) transmission-coefficient between antennas #1&#9 (S<sub>19</sub>).</figcaption></figure>

time-domain finite integration technique (FIT) method.

The active S-parameters in Fig. 2(a) shows that the proposed basic antenna array exhibits an impedance bandwidth of 700 MHz and operates across 26.5–27.2 GHz, which corresponds to a the fractional bandwidth (FBW) of 2.6%. The transmission-coefficient response between the radiation elements is shown in Fig. 2(b)-(i). These results show that the average isolation between the patches #2 to #9
<table><caption>**Table 2**
S-Parameters Of The Various Antenna Array Structures.</caption><thead><tr><th>Antenna Arrays</th><th>Reflection coefficient (S<sub>11</sub> &lt;−10 dB)</th></tr></thead><tbody><tr><td>Basic array</td><td>26.5–27.2 GHz (700 MHz &amp; 2.6% FBW)</td></tr><tr><td>Array with wall</td><td>24.8–28.4 GHz (3.6 GHz &amp;13.5% FBW)</td></tr><tr><td>Array with slots</td><td>24.0–28.4 GHz (4.4 GHz &amp; 16.8% FBW)</td></tr><tr><td>Improvement of slot array c.f. basic array</td><td>3.7 GHz &amp; 14.2% FBW</td></tr><tr><th>Antenna Arrays</th><th>Average transmission coefficient (dB)</th></tr><tr><td></td><td>S<sub>12</sub></td></tr><tr><td>Basic array</td><td>12</td></tr><tr><td>Array with wall</td><td>17</td></tr><tr><td>Array with slot load</td><td>23</td></tr><tr><td>Improvement of slot array c.f. basic array</td><td>11</td></tr></tbody></table><table><thead><tr><th>S<sub>13</sub></th><th>S<sub>14</sub></th><th>S<sub>15</sub></th><th>S<sub>16</sub></th><th>S<sub>17</sub></th><th>S<sub>18</sub></th><th>S<sub>19</sub></th></tr></thead><tbody><tr><td>6</td><td>11</td><td>7</td><td>11</td><td>12</td><td>10</td><td>13</td></tr><tr><td>14</td><td>20</td><td>17</td><td>16</td><td>18</td><td>16</td><td>19</td></tr><tr><td>22</td><td>27</td><td>22</td><td>23</td><td>24</td><td>23</td><td>30</td></tr><tr><td>16</td><td>16</td><td>15</td><td>12</td><td>12</td><td>13</td><td>17</td></tr></tbody></table>

<figure><img src="image_6.png" /><figcaption>**Fig. 3.** Radiation properties of the antenna array, (a) gain, and (b) efficiency.</figcaption></figure>

<table><caption>**Table 3**
Radiation Characteristics With CST.</caption><tbody><tr><th colspan="2">Average gain (dBi)</th></tr><tr><td>Basic array</td><td>9.5</td></tr><tr><td>Array with wall</td><td>15.7</td></tr><tr><td>Array with slot load</td><td>20.5</td></tr><tr><td>Improvement of slot array c.f. basic array</td><td>10.5</td></tr><tr><th colspan="2">Average efficiency (%)</th></tr><tr><td>Basic array</td><td>68</td></tr><tr><td>Array with wall</td><td>82</td></tr><tr><td>Array with slot load</td><td>93.5</td></tr><tr><td>Improvement of slot array c.f. basic array</td><td>25</td></tr></tbody></table>

relative to patch #1, i.e., the isolation between patches #1&#2 is 12 dB, #1&#3 is 6 dB, #1&#4 is 11 dB, #1&#5 is 7 dB, #1&#6 is 11 dB, #1&#7 is 12 dB, #1&#8 is 10 dB, and #1&#9 is 13 dB. The results are summarized in Table 2.

The radiation characteristics of the proposed antenna array are shown in Fig. 3. It can be observed from this figure that an average gain and efficiency achieved over the antenna's operating frequency band of 26.5–27.2 GHz are 9.5 dBi and 68%, respectively. The radiation characteristics of the antenna array are summarized in Table 3.

Mutual coupling effects between the closely spaced radiating elements can cause unwanted distortion in the radiation characteristics of the array. This can adversely affect the overall far-field performance of the antenna array. Therefore, to suppress the near-field radiation emanating from each antenna in the array, an isolation wall wrapped around the individual antennas, as shown in Fig. 4. The wall is made from a perfect electric conductor. This simple technique does not affect the overall size of the antenna.

The active S-parameters and radiation properties of the array with the isolation wall are shown in Figs. 2 and 3. These results show that with the isolation wall the impedance bandwidth of the antenna array improves by a factor of four across 24.8–28.4 GHz, which corresponds to a fractional bandwidth of 13.5%. The transmission-coefficient response in Fig. 2(b)-(i) show that the improvement in the average isolation between antennas #1&#2 is 5 dB, #1&#3 is 8 dB, #1&#4 is 9 dB, #1&#5 is 10 dB, #1&#6 is 5 dB, #1&#7 is 6 dB, and #1&#8 is 6 dB, and #1&#9 is 6 dB. These results are compared with the basic array in Table 2.
<table><caption>**Table 2**
S-Parameters Of The Various Antenna Array Structures.</caption><thead><tr><th>Antenna Arrays</th><th>Reflection coefficient (S<sub>11</sub> &lt;−10 dB)</th></tr></thead><tbody><tr><td>Basic array</td><td>26.5–27.2 GHz (700 MHz &amp; 2.6% FBW)</td></tr><tr><td>Array with wall</td><td>24.8–28.4 GHz (3.6 GHz &amp;13.5% FBW)</td></tr><tr><td>Array with slots</td><td>24.0–28.4 GHz (4.4 GHz &amp; 16.8% FBW)</td></tr><tr><td>Improvement of slot array c.f. basic array</td><td>3.7 GHz &amp; 14.2% FBW</td></tr><tr><th>Antenna Arrays</th><th>Average transmission coefficient (dB)</th></tr><tr><td></td><td>S<sub>12</sub></td></tr><tr><td>Basic array</td><td>12</td></tr><tr><td>Array with wall</td><td>17</td></tr><tr><td>Array with slot load</td><td>23</td></tr><tr><td>Improvement of slot array c.f. basic array</td><td>11</td></tr></tbody></table><table><thead><tr><th>S<sub>13</sub></th><th>S<sub>14</sub></th><th>S<sub>15</sub></th><th>S<sub>16</sub></th><th>S<sub>17</sub></th><th>S<sub>18</sub></th><th>S<sub>19</sub></th></tr></thead><tbody><tr><td>6</td><td>11</td><td>7</td><td>11</td><td>12</td><td>10</td><td>13</td></tr><tr><td>14</td><td>20</td><td>17</td><td>16</td><td>18</td><td>16</td><td>19</td></tr><tr><td>22</td><td>27</td><td>22</td><td>23</td><td>24</td><td>23</td><td>30</td></tr><tr><td>16</td><td>16</td><td>15</td><td>12</td><td>12</td><td>13</td><td>17</td></tr></tbody></table>

<figure><img src="image_7.png" /><figcaption>**Fig. 3.** Radiation properties of the antenna array, (a) gain, and (b) efficiency.</figcaption></figure>

<table><caption>**Table 3**
Radiation Characteristics With CST.</caption><tbody><tr><th colspan="2">Average gain (dBi)</th></tr><tr><td>Basic array</td><td>9.5</td></tr><tr><td>Array with wall</td><td>15.7</td></tr><tr><td>Array with slot load</td><td>20.5</td></tr><tr><td>Improvement of slot array c.f. basic array</td><td>10.5</td></tr><tr><th colspan="2">Average efficiency (%)</th></tr><tr><td>Basic array</td><td>68</td></tr><tr><td>Array with wall</td><td>82</td></tr><tr><td>Array with slot load</td><td>93.5</td></tr><tr><td>Improvement of slot array c.f. basic array</td><td>25</td></tr></tbody></table>

relative to patch #1, i.e., the isolation between patches #1&#2 is 12 dB, #1&#3 is 6 dB, #1&#4 is 11 dB, #1&#5 is 7 dB, #1&#6 is 11 dB, #1&#7 is 12 dB, #1&#8 is 10 dB, and #1&#9 is 13 dB. The results are summarized in Table 2.

The radiation characteristics of the proposed antenna array are shown in Fig. 3. It can be observed from this figure that an average gain and efficiency achieved over the antenna’s operating frequency band of 26.5–27.2 GHz are 9.5 dBi and 68%, respectively. The radiation characteristics of the antenna array are summarized in Table 3.

Mutual coupling effects between the closely spaced radiating elements can cause unwanted distortion in the radiation characteristics of the array. This can adversely affect the overall far-field performance of the antenna array. Therefore, to suppress the near-field radiation emanating from each antenna in the array, an isolation wall wrapped around the individual antennas, as shown in Fig. 4. The wall is made from a perfect electric conductor. This simple technique does not affect the overall size of the antenna.

The active S-parameters and radiation properties of the array with the isolation wall are shown in Figs. 2 and 3. These results show that with the isolation wall the impedance bandwidth of the antenna array improves by a factor of four across 24.8–28.4 GHz, which corresponds to a fractional bandwidth of 13.5%. The transmission-coefficient response in Fig. 2(b)-(i) show that the improvement in the average isolation between antennas #1&#2 is 5 dB, #1&#3 is 8 dB, #1&#4 is 9 dB, #1&#5 is 10 dB, #1&#6 is 5 dB, #1&#7 is 6 dB, and #1&#8 is 6 dB, and #1&#9 is 6 dB. These results are compared with the basic array in Table 2.
<figure><img src="image_7.png" /><figcaption>**Fig. 4.** Antenna Array with the isolation walls, (a) isometric top-view, (b) schematic top-view to show the location of each structural element, and (c) side-view.</figcaption></figure>

Fig. 3 shows that CST predicts the average gain and efficiency of the antenna array to be 20.5 dBi and 93.5%, respectively, over 24.8–28.4 GHz. Compared to the basic array this corresponds to an average improvement in gain and efficiency of 10.5 dBi and 25%, respectively. With HFSS the average gain and efficiency are 19.2 dBi and 85%, respectfully. These results are compared in Table 3.

In order to improve the antenna’s performance, the hexagonal-shaped patches are loaded with hexagonal-shaped slot rings of decreasing diameter, as shown in Fig. 5. The rings are of subwavelength circumference and the width of the slots is 0.08 mm. When the slot loaded patches are exposed to EM-waves they behave like a metasurface as described in [13–15] that has an effect of magnify the aperture of the antenna array. Results from the 3-D EM-solvers, i.e., CST Microwave Studio and Ansoft HFSS, in Figs. 2 and 3 demonstrate that by introducing the slots the array’s performance is improved. This is achieved without increasing the physical size of the antenna array. Moreover, the results show that the slots increase the array’s impedance bandwidth by 4.4 GHz. Compared to the basic array in Fig. 1 the bandwidth is increased by a factor of approximately six.

Fig. 2(b)-(i) show the average isolation improvement of the antennas #2 to #9 relative to antenna #1 in respectively order is: 11 dB, 16 dB, 16 dB, 15 dB, 12 dB, 12 dB, 13 dB, and 17 dB. The average isolation of the slotted patches in sequence from #2 to #9 with respect to antenna #1 is: 23 dB, 22 dB, 27 dB, 22 dB, 23 dB, 24 dB, 23 dB, and 30 dB. Fig. 3 shows that with the slot loaded patch the gain and radiation efficiency improve significantly compared to the basic array in Fig. 1. On average the gain increases by 10.5 dB and the efficiency increases by 25%. These results are compared in Table 2.

The radiation characteristics of the proposed antenna array structure in its various forms, i.e., basic ‘with’ and ‘without’ the isolation wall and metasurface slots, are compared in Table 3. It is shown that the array structure with the isolation wall and metasurface provides superior antenna performance. The excellent correlation between the two different 3-D numerical solvers shows the viability of the proposed array for millimeter-wave applications such as 5 G wireless communications.

Comparison of the proposed antenna with the previously published antenna arrays operating in the same band is presented in Table 4. The comparison parameters include dimensions, substrate properties, bandwidth (BW), radiation gain, and efficiency. The comparison shows that the key performance of gain and efficiency are not possible with the other array approaches reported thus far considering the compact footprint area of the proposed array antenna.
<figure><img src="image_8.png" /><figcaption>**Fig. 4.** Antenna Array with the isolation walls, (a) isometric top-view, (b) schematic top-view to show the location of each structural element, and (c) side-view.</figcaption></figure>

Fig. 3 shows that CST predicts the average gain and efficiency of the antenna array to be 20.5 dBi and 93.5%, respectively, over 24.8–28.4 GHz. Compared to the basic array this corresponds to an average improvement in gain and efficiency of 10.5 dBi and 25%, respectively. With HFSS the average gain and efficiency are 19.2 dBi and 85%, respectfully. These results are compared in Table 3.

In order to improve the antenna’s performance, the hexagonal-shaped patches are loaded with hexagonal-shaped slot rings of decreasing diameter, as shown in Fig. 5. The rings are of subwavelength circumference and the width of the slots is 0.08 mm. When the slot loaded patches are exposed to EM-waves they behave like a metasurface as described in [13–15] that has an effect of magnify the aperture of the antenna array. Results from the 3-D EM-solvers, i.e., CST Microwave Studio and Ansoft HFSS, in Figs. 2 and 3 demonstrate that by introducing the slots the array’s performance is improved. This is achieved without increasing the physical size of the antenna array. Moreover, the results show that the slots increase the array’s impedance bandwidth by 4.4 GHz. Compared to the basic array in Fig. 1 the bandwidth is increased by a factor of approximately six.

Fig. 2(b)-(i) show the average isolation improvement of the antennas #2 to #9 relative to antenna #1 in respectively order is: 11 dB, 16 dB, 16 dB, 15 dB, 12 dB, 12 dB, 13 dB, and 17 dB. The average isolation of the slotted patches in sequence from #2 to #9 with respect to antenna #1 is: 23 dB, 22 dB, 27 dB, 22 dB, 23 dB, 24 dB, 23 dB, and 30 dB. Fig. 3 shows that with the slot loaded patch the gain and radiation efficiency improve significantly compared to the basic array in Fig. 1. On average the gain increases by 10.5 dB and the efficiency increases by 25%. These results are compared in Table 2.

The radiation characteristics of the proposed antenna array structure in its various forms, i.e., basic ‘with’ and ‘without’ the isolation wall and metasurface slots, are compared in Table 3. It is shown that the array structure with the isolation wall and metasurface provides superior antenna performance. The excellent correlation between the two different 3-D numerical solvers shows the viability of the proposed array for millimeter-wave applications such as 5 G wireless communications.

Comparison of the proposed antenna with the previously published antenna arrays operating in the same band is presented in Table 4. The comparison parameters include dimensions, substrate properties, bandwidth (BW), radiation gain, and efficiency. The comparison shows that the key performance of gain and efficiency are not possible with the other array approaches reported thus far considering the compact footprint area of the proposed array antenna.
<figure><img src="image_8.png" /><figcaption>**Fig. 5.** Proposed array antennas with isolation walls and loaded with metasurface slots, (a) isometric top-view, (b) schematic top-view to show the location of the geometrical parameters, (c) side view with zoomed single antenna to better displaying the feeding mechanism, and (d) schematic bottom-view to show the precise location of the structural parameters.</figcaption></figure>

<table><caption>**Table 4**

Proposed Antenna Array Compared With Other Arrays Reported In Literature.</caption><thead><tr><td>Ref.</td><td>Size (mm²)</td><td>Substrate</td><td>Bandwidth /freq. range (GHz)</td><td>Gain (dBi)</td><td>Eff. (%)</td></tr></thead><tbody><tr><td>[16]</td><td>20 × 20</td><td>Two different layers: (i) 1 mm FR4 (ii) 0.254 mm RO4350B</td><td>5.25 / 24.25–29.5</td><td>Max. 10</td><td>Max. 85</td></tr><tr><td>[17]</td><td>99.2 × 17.45</td><td>0.254 mm Rogers 5880</td><td>6.78 /24.35–31.13</td><td>Max. 19.88</td><td>Max. 86</td></tr><tr><td>[18]</td><td>27 × 25</td><td>0.508 mm Roger 4003 C</td><td>5 / 24–29</td><td>Max. 9</td><td>–</td></tr><tr><td>[19]</td><td>130 × 90</td><td>0.508 mm RO4003C</td><td>3 / 28–3</td><td>Max. 9.6</td><td>–</td></tr><tr><td>This work</td><td>20 × 20</td><td>0.8 mm Rogers RT5880</td><td>4.4 / 24.0–28.4</td><td>Max. 21</td><td>Max. 98</td></tr></tbody></table>

### 3. Conclusion

A novel and compact nine element antenna array with shared aperture configuration is shown to exhibit high-gain and high radiation efficiency at the millimeter-wave 5 G band. The 3 × 3 matrix antenna array is composed of hexagonal-shaped patches that are suspended above a common substrate and excited by metallic rods through the substrate. To minimize the adverse effects of mutual coupling between the radiators the individual antenna elements in the array were surrounded with a metallic wall. The patches were embedded with hexagonal-shaped slots to transform them to a metasurface. The proposed array structure exhibits an average gain and efficiency of 20 dBi and 93%, respectively, with isolation between the radiating elements better than 22 dB.

### Declaration of Competing Interest

The authors confirm that they do not have conflict of interest.
<figure><img src="image_9.png" /><figcaption>**Fig. 5.** Proposed array antennas with isolation walls and loaded with metasurface slots, (a) isometric top-view, (b) schematic top-view to show the location of the geometrical parameters, (c) side view with zoomed single antenna to better displaying the feeding mechanism, and (d) schematic bottom-view to show the precise location of the structural parameters.</figcaption></figure>

<table><caption>**Table 4**
Proposed Antenna Array Compared With Other Arrays Reported In Literature.</caption><thead><tr><td>Ref.</td><td>Size (mm²)</td><td>Substrate</td><td>Bandwidth /freq. range (GHz)</td><td>Gain (dBi)</td><td>Eff. (%)</td></tr></thead><tbody><tr><td>[16]</td><td>20 × 20</td><td>Two different layers: (i) 1 mm FR4 (ii) 0.254 mm RO4350B</td><td>5.25 / 24.25–29.5</td><td>Max. 10</td><td>Max. 85</td></tr><tr><td>[17]</td><td>99.2 × 17.45</td><td>0.254 mm RO4350B<br>Rogers 5880</td><td>6.78 /24.35–31.13</td><td>Max. 19.88</td><td>Max. 86</td></tr><tr><td>[18]</td><td>27 × 25</td><td>0.508 mm<br>Roger 4003 C</td><td>5 / 24–29</td><td>Max. 9</td><td>–</td></tr><tr><td>[19]</td><td>130 × 90</td><td>0.508 mm<br>RO4003C</td><td>3 / 28–3</td><td>Max. 9.6</td><td>–</td></tr><tr><td>This work</td><td>20 × 20</td><td>0.8 mm Rogers RT5880</td><td>4.4 / 24.0–28.4</td><td>Max. 21</td><td>Max. 98</td></tr></tbody></table>

### 3. Conclusion

A novel and compact nine element antenna array with shared aperture configuration is shown to exhibit high-gain and high radiation efficiency at the millimeter-wave 5 G band. The 3 × 3 matrix antenna array is composed of hexagonal-shaped patches that are suspended above a common substrate and excited by metallic rods through the substrate. To minimize the adverse effects of mutual coupling between the radiators the individual antenna elements in the array were surrounded with a metallic wall. The patches were embedded with hexagonal-shaped slots to transform them to a metasurface. The proposed array structure exhibits an average gain and efficiency of 20 dBi and 93%, respectively, with isolation between the radiating elements better than 22 dB.

### Declaration of Competing Interest

The authors confirm that they do not have conflict of interest.
Acknowledgment

Dr. Mohammad Alibakhshikenari acknowledges support from the CONEX-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. Also, this work was supported by Project RTI2018-095499-B-C31, funded by the Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER, UE).

References

[1] T.S. Rappaport, Y. Xing, G.R. MacCartney, A.F. Molisch, E. Mellios, J. Zhang, Overview of millimeter wave communications for fifth-generation (5G) wireless networks—with a focus on propagation models, IEEE Trans. Antennas Propag. vol. 65 (12) (2017) 6213–6230.

[2] W. Hong, K.-H. Baek, Y. Lee, Y. Kim, S.-T. Ko, Study and prototyping of practically large-scale mmWave antenna systems for 5G cellular devices, IEEE Commun. Mag. vol. 52 (9) (2014) 63–69.

[3] D. Lockie, D. Peck, High-data-rate millimeter-wave radios, IEEE Microw. Mag. vol. 10 (5) (2009) 75–83.

[4] J. Zhu, S. Liao, S. Li, Q. Xue, 60 GHz Wideband high-gain circularly polarized antenna array with substrate integrated cavity excitation, IEEE Antennas Wirel. Propag. Lett. vol. 17 (5) (2018) 751–755.

[5] J. Wu, Y.J. Cheng, Y. Fan, Millimeter-wave wideband high-efficiency circularly polarized planar array antenna, IEEE Trans. Antennas Propag. vol. 64 (2) (2016) 535–542.

[6] S.K. Agrawal and K. Sharma, “5G millimeter wave (mmWave) communications,” 2016 3rd International Conference on Computing for Sustainable Global Development (INDIACom), Mar. 2016, pp. 3630–3634.

[7] M. Alibakhshikenari, B.S. Virdee, A.A. Althuwayb, et al., Study on on-chip antenna design based on metamaterial-inspired and substrate-integrated waveguide properties for millimetre-wave and THz integrated-circuit applications, J. Infrared, Millim., Terahertz Waves vol. 42 (2021) 17–28.

[8] L. Wei, R.Q. Hu, Y. Qian, G. Wu, Key elements to enable millimeter wave communications for 5G wireless systems, IEEE Wirel. Commun. vol. 21 (6) (2014) 136–143.

[9] V.L. Nguyen, P. Lin, R. Hwang, Enhancing misbehavior detection in 5G vehicle-to-vehicle communications, IEEE Trans. Veh. Technol. vol. 69 (issue 9) (2020) 9417–9430.

[10] S.J. Li, Y.B. Li, L. Zhang, Z.J. Luo, B.W. Han, R.Q. Li, X.Y. Cao, Q. Cheng, T.J. Cui, Programmable controls to scattering properties of a radiation array, Laser Photonics Rev. vol. 15 (2000449) (2021) 1–9.

[11] S.J. Li, Y.B. Li, R.Q. Li, Q. Cheng, T.J. Cui, Digital-coding-feeding metasurfaces for differently polarized wave emission, orbit angular momentum generation, and scattering manipulation, Adv. Photonics Res. vol. 1 (2020) 2000012.

[12] M. Alibakhshikenari, B.S. Virdee, et al., Singular integral formulations for electrodynamic analysis of metamaterial-inspired antenna array, IEEE Antennas Wirel. Propag. Lett. vol. 20 (2) (2021) 179–183.

[13] S.S. Bukhari, J. Vardaxoglou, W. Whittow, A metasurfaces review: definitions and applications, Appl. Sci. vol. 9 (2727) (2019) 1–14.

[14] Z. Wang, C. Li, Y. Yin, A meta-surface antenna array decoupling (MAAD) design to improve the isolation performance in a MIMO system, IEEE Access vol. 8 (2020) pp.61797-61085.

[15] W. Zhang, C. Song, R. Pei, Y. Huang, J. Zhou, Broadband metasurface antenna using hexagonal loop-shaped unit cells, IEEE Access vol. 8 (2020) 223797–223805.

[16] I. Lima de Paula, et al., Cost-effective high-performance air-filled siw antenna array for the global 5G 26 GHz and 28 GHz bands, IEEE Antennas Wirel. Propag. Lett. vol. 20 (2) (2021) 194–198.

[17] M. Khalily, R. Tafazolli, P. Xiao, A.A. Kishk, Broadband mm-wave microstrip array antenna with improved radiation characteristics for different 5G applications, IEEE Trans. Antennas Propag. vol. 66 (9) (2018) 4641–4647.

[18] M. Borhani Kakhki, M. Mantash, A. Kesavan, M.M. Tahseen, T.A. Denidni, Millimeter-wave beam-tilting vivaldi antenna with gain enhancement using multilayer FSS, IEEE Antennas Wirel. Propag. Lett. vol. 17 (12) (2018) 2279–2283.

[19] M. Mantash, A. Kesavan, T.A. Denidni, Beam-tilting endfire antenna using a single-layer FSS for 5G communication networks, IEEE Antennas Wirel. Propag. Lett. vol. 17 (1) (2018) 29–33.

<figure><img src="image_9.png" /></figure>

Mohammad Alibakhshikenari was born in Mazandaran, Iran, in February 1988. He received the Ph.D. degree (Hons.) with European Label in electronics engineering from the University of Rome “Tor Vergata”, Italy, in February 2020. He was a Ph.D. Visiting Researcher with the Chalmers University of Technology, Sweden, in 2018. His training during the Ph.D. included a research stage in the Swedish company Gap Waves AB. He is currently with the Department of Signal Theory and Communications, Universidad Carlos III de Madrid (uc3m), Spain, as a Principal Investigator of the CONEX-Plus Talent Training Program and Marie Skłodowska-Curie Actions. He is also a lecturer of the “electromagnetic fields” and “electromagnetic laboratory” in the department. For academic year 2021/2022, he received the “Teaching Excellent Acknowledgement” certificate for the course of electromagnetic fields from Vice-rector of studies of uc3m. His research interests include electromagnetic systems, antennas and wave-propagations, metamaterials and metasurfaces, synthetic aperture radars (SAR), 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). The above research lines have produced more than 200 publications on international journals, presentations within international conferences, and book chapters with a total number of the citations more than 3200 and H-index of 40. He was a recipient of the three years research grant funded by Universidad Carlos III de Madrid and the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie Grant 801538 started in July 2021, the two years 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 held in Nuremberg, Germany, in 2017, and in Madrid, Spain, in 2018, respectively. His research article entitled “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, UK, in April 2020. He is serving as an Associate Editor for *IET Journal of Engineering and International Journal of Antennas and Propagation*. He also acts as a referee in several highly reputed journals and international conferences.
## Acknowledgment

Dr. Mohammad Alibakhshikenari acknowledges support from the CONEX-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. Also, this work was supported by Project RTI2018-095499-B-C31, funded by the Ministerio de Ciencia, Innovación y Universidades, Gobierno de España (MCIU/AEI/FEDER, UE).

## References

[1] T.S. Rappaport, Y. Xing, G.R. MacCartney, A.F. Molisch, E. Mellios, J. Zhang, Overview of millimeter wave communications for fifth-generation (5G) wireless networks—with a focus on propagation models, IEEE Trans. Antennas Propag. vol. 65 (12) (2017) 6213–6230.

[2] W. Hong, K.-H. Baek, Y. Lee, Y. Kim, S.-T. Ko, Study and prototyping of practically large-scale mmWave antenna systems for 5G cellular devices, IEEE Commun. Mag. vol. 52 (9) (2014) 63–69.

[3] D. Lockie, D. Peck, High-data-rate millimeter-wave radios, IEEE Microw. Mag. vol. 10 (5) (2009) 75–83.

[4] J. Zhu, S. Liao, S. Li, Q. Xue, 60 GHz Wideband high-gain circularly polarized antenna array with substrate integrated cavity excitation, IEEE Antennas Wirel. Propag. Lett. vol. 17 (5) (2018) 751–755.

[5] J. Wu, Y.J. Cheng, Y. Fan, Millimeter-wave wideband high-efficiency circularly polarized planar array antenna, IEEE Trans. Antennas Propag. vol. 64 (2) (2016) 535–542.

[6] S.K. Agrawal and K. Sharma, “5G millimeter wave (mmWave) communications,” 2016 3rd International Conference on Computing for Sustainable Global Development (INDIACOM), Mar. 2016, pp. 3630–3634.

[7] M. Alibakhshikenari, B.S. Virdee, A.A. Althuwayb, et al., Study on on-chip antenna design based on metamaterial-inspired and substrate-integrated waveguide properties for millimetre-wave and THz integrated-circuit applications, J. Infrared, Millim., Terahertz Waves vol. 42 (2021) 17–28.

[8] L. Wei, R.Q. Hu, Y. Qian, G. Wu, Key elements to enable millimeter wave communications for 5G wireless systems, IEEE Wirel. Commun. vol. 21 (6) (2014) 136–143.

[9] V.L. Nguyen, P. Lin, R. Hwang, Enhancing misbehavior detection in 5G vehicle-to-vehicle communications, IEEE Trans. Veh. Technol. vol. 69 (issue 9) (2020) 9417–9430.

[10] S.J. Li, Y.B. Li, L. Zhang, Z.J. Luo, B.W. Han, R.Q. Li, X.Y. Cao, Q. Cheng, T.J. Cui, Programmable controls to scattering properties of a radiation array, Laser Photonics Rev. vol. 15 (2000449) (2021) 1–9.

[11] S.J. Li, Y.B. Li, R.Q. Li, Q. Cheng, T.J. Cui, Digital-coding-feeding metasurfaces for differently polarized wave emission, orbit angular momentum generation, and scattering manipulation, Adv. Photonics Res. vol. 1 (2020) 2000012.

[12] M. Alibakhshikenari, B.S. Virdee, et al., Singular integral formulations for electrodynamic analysis of metamaterial-inspired antenna array, IEEE Antennas Wirel. Propag. Lett. vol. 20 (2) (2021) 179–183.

[13] S.S. Bukhari, J. Vardaxoglou, W. Whittow, A metasurfaces review: definitions and applications, Appl. Sci. vol. 9 (2727) (2019) 1–14.

[14] Z. Wang, C. Li, Y. Yin, A meta-surface antenna array decoupling (MAAD) design to improve the isolation performance in a MIMO system, IEEE Access vol. 8 (2020) pp.61797-61085.

[15] W. Zhang, C. Song, R. Pei, Y. Huang, J. Zhou, Broadband metasurface antenna using hexagonal loop-shaped unit cells, IEEE Access vol. 8 (2020) 223797–223805.

[16] I. Lima de Paula, et al., Cost-effective high-performance air-filled siw antenna array for the global 5G 26 GHz and 28 GHz bands, IEEE Antennas Wirel. Propag. Lett. vol. 20 (2) (2021) 194–198.

[17] M. Khalily, R. Tafazolli, P. Xiao, A.A. Kishk, Broadband mm-wave microstrip array antenna with improved radiation characteristics for different 5G applications, IEEE Trans. Antennas Propag. vol. 66 (9) (2018) 4641–4647.

[18] M. Borhani Kakhki, M. Mantash, A. Kesavan, M.M. Tahseen, T.A. Denidni, Millimeter-wave beam-tilting vivaldi antenna with gain enhancement using multilayer FSS, IEEE Antennas Wirel. Propag. Lett. vol. 17 (12) (2018) 2279–2283.

[19] M. Mantash, A. Kesavan, T.A. Denidni, Beam-tilting endfire antenna using a single-layer FSS for 5G communication networks, IEEE Antennas Wirel. Propag. Lett. vol. 17 (1) (2018) 29–33.

<figure><img src="image_10.png" /></figure>

Mohammad Alibakhshikenari was born in Mazandaran, Iran, in February 1988. He received the Ph.D. degree (Hons.) with European Label in electronics engineering from the University of Rome “Tor Vergata”, Italy, in February 2020. He was a Ph.D. Visiting Researcher with the Chalmers University of Technology, Sweden, in 2018. His training during the Ph.D. included a research stage in the Swedish company Gap Waves AB. He is currently with the Department of Signal Theory and Communications, Universidad Carlos III de Madrid (uc3m), Spain, as a Principal Investigator of the CONEX-Plus Talent Training Program and Marie Skłodowska-Curie Actions. He is also a lecturer of the “electromagnetic fields” and “electromagnetic laboratory” in the department. For academic year 2021/2022, he received the “Teaching Excellent Acknowledgement” certificate for the course of electromagnetic fields from Vice-rector of studies of uc3m. His research interests include electromagnetic systems, antennas and wave-propagations, metamaterials and metasurfaces, synthetic aperture radars (SAR), 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). The above research lines have produced more than 200 publications on international journals, presentations within international conferences, and book chapters with a total number of the citations more than 3200 and H-index of 40. He was a recipient of the three years research grant funded by Universidad Carlos III de Madrid and the European Union’s Horizon 2020 Research and Innovation Program under the Marie Skłodowska-Curie Grant 801538 started in July 2021, the two years 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 held in Nuremberg, Germany, in 2017, and in Madrid, Spain, in 2018, respectively. His research article entitled “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, UK, in April 2020. He is serving as an Associate Editor for *IET Journal of Engineering and International Journal of Antennas and Propagation*. He also acts as a referee in several highly reputed journals and international conferences.
<figure><img src="image_10.png" /></figure>

**Bal S. Virdee** received the B.Sc. and MPhil degrees in Communications-Engineering from the University of Leeds-UK and his Ph.D. in Electronic-Engineering from the University of London-UK. He has worked in industry for various companies including Philips (UK) as an R&D-engineer and Filtronic-Components Ltd. as a future products developer in the area of RF/microwave communications. He has taught at several academic institutions before joining London Metropolitan University where he is a Professor of Microwave-Communications in the Faculty of Life Sciences&Computing where he Heads the Center for Communications-Technology and is the Director of London Metropolitan-Microwaves. His research, in collaboration with industry and academia, is in the area of microwave wireless communications encompassing mobile-phones to satellite-technology. Prof. Virdee has chaired technical sessions at IEEE international conferences and published numerous research-papers. He is Executive-Member of IET's Technical and Professional Network Committee on RF/Microwave-Technology. He is a Fellow of IET and a Senior-Member of IEEE.

<figure><img src="image_11.png" /></figure>

**Valeria Vadalà** was born in Reggio Calabria, Italy, in 1982. She received the M.S. degree cum laude in electronic engineering from the "Mediterranea" University of Reggio Calabria, Reggio Calabria, Italy, in 2006 and the Ph.D. degree in information engineering from the University of Ferrara, Ferrara, Italy, in 2010. In 2013 she was invited to spend a period as Visiting Fellow at the Telecommunication and Microwave Laboratory (TELEMIC) at the Engineering department of KU Leuven University in Belgium. She is currently Assistant Professor at the Department of Physics, University of Milano-Bicocca where she teaches the course of electronic instrumentation and measurement. Her current research interests include nonlinear electron-device characterization and modeling and circuit-design techniques for nonlinear microwave and millimeter wave applications.

<figure><img src="image_12.png" /></figure>

**Mariana Dalarsson** received the M.Sc. degree in physics and Ph.D. degree in electromagnetic theory from KTH Royal Institute of Technology, Stockholm, Sweden, in 2010 and 2016, respectively. She received the Honorary Grant given to the best graduate of the year of her M. Sc. programme, in 2011. She is also the second youngest woman ever to be awarded a Ph.D. degree from KTH. During 2016–2019, she was a postdoctoral researcher with the Group of Waves, Signals and Systems at Linnaeus University, Växjö, Sweden. In 2019, she was awarded the Docent degree from the same university. From 2019 to 2010, she was an Assistant Professor at the Department of Electrical and Information Technology, Lund University, Lund, Sweden. Currently, she is an Assistant Professor at KTH Royal Institute of Technology, Stockholm, Sweden. She is the author of more than 60 scientific publications, including 25 journal papers and one book. Her teaching and research interests include electromagnetic scattering and absorption, inverse problems, electromagnetics of stratified media, double-negative metamaterials, mathematical physics, etc. Currently, she is mainly pursuing research as PI within her own project grant "Waveguide theory for artificial materials and plasmonics" awarded by the Swedish Research Council. She is the winner of multiple teaching and research awards, including the L'Oréal-Unesco For Women in Science Sweden Award in 2021.

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

**María Elena De Cos Gómez** received the M.S. and Ph.D. degrees from the Universidad de Cantabria, in 2002 and 2006, respectively. She was involved in nonlinear dynamics: stability and phase-noise analysis of nonlinear circuits, such as oscillators, frequency dividers, self-oscillating mixers, and multiharmonic generators. She was a Researcher Engineer in collaboration with ACORDE S.A from 2004 to 2007. She joined TSC-UNIOVI in 2007. She was an Invited Professor with the I.E.T.R. Rennes, France, in 2011 and 2014, respectively. She was an Associate Editor of the International Journal of Antennas and Propagation. Her research interests are metamaterials design and its applications to antennas and microwave circuits, design of antennas for RFID systems, location techniques, and wireless sensor networks design and applications.

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

**Abdullah G. Alharbi** received the B.Sc. degree in electronics and communications engineering from Qassim University, Saudi Arabia, in 2010, the master and PhDs degree in electrical engineering from the University of Missouri Kansas City, USA, in 2014, 2017, respectively. From 2010 to 2012, he was an Electrical Engineer with Saudi Aramco Company. He is currently an Assistant Professor with the Electrical Engineering Department, Jouf University, Saudi Arabia. He authored and co-authored over 45 journal and conference papers and one Springer book. His research interests include digital IC design, Memristor-based circuits, nanoelectronics, Network Routing, Green Communications, and wireless communications. He was a recipient of several awards from Saudi Arabian Cultural Mission in USA, and the University of Missouri Kansas City. He is a member of the Gulf Engineering Union, the IEEE Circuits and Systems Society, the IEEE Young Professionals, the IEEE Signal Processing Society, the IEEE Instrumentation and Measurement Society Membership, and the IEEE Communications Society Membership, and a Professional Member of ACM.
<figure><img src="image_11.png" /></figure>

**Bal S. Virdee** received the B.Sc. and MPhil degrees in Communications-Engineering from the University of Leeds-UK and his Ph.D. in Electronic-Engineering from the University of London-UK. He has worked in industry for various companies including Philips (UK) as an R&D-engineer and Filtronic-Components Ltd. as a future products developer in the area of RF/microwave communications. He has taught at several academic institutions before joining London Metropolitan University where he is a Professor of Microwave-Communications in the Faculty of Life Sciences&Computing where he Heads the Center for Communications-Technology and is the Director of London Metropolitan-Microwaves. His research, in collaboration with industry and academia, is in the area of microwave wireless communications encompassing mobile-phones to satellite-technology. Prof. Virdee has chaired technical sessions at IEEE international conferences and published numerous research-papers. He is Executive-Member of IET's Technical and Professional Network Committee on RF/Microwave-Technology. He is a Fellow of IET and a Senior-Member of IEEE.

<figure><img src="image_12.png" /></figure>

**Valeria Vadalà** was born in Reggio Calabria, Italy, in 1982. She received the M.S. degree cum laude in electronic engineering from the "Mediterranea" University of Reggio Calabria, Reggio Calabria, Italy, in 2006 and the Ph.D. degree in information engineering from the University of Ferrara, Ferrara, Italy, in 2010. In 2013 she was invited to spend a period as Visiting Fellow at the Telecommunication and Microwave Laboratory (TELEMIC) at the Engineering department of KU Leuven University in Belgium. She is currently Assistant Professor at the Department of Physics, University of Milano-Bicocca where she teaches the course of electronic instrumentation and measurement. Her current research interests include nonlinear electron-device characterization and modeling and circuit-design techniques for nonlinear microwave and millimeter wave applications.

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

**Mariana Dalarsson** received the M.Sc. degree in physics and Ph.D. degree in electromagnetic theory from KTH Royal Institute of Technology, Stockholm, Sweden, in 2010 and 2016, respectively. She received the Honorary Grant given to the best graduate of the year of her M. Sc. programme, in 2011. She is also the second youngest woman ever to be awarded a Ph.D. degree from KTH. During 2016–2019, she was a postdoctoral researcher with the Group of Waves, Signals and Systems at Linnaeus University, Växjö, Sweden. In 2019, she was awarded the Docent degree from the same university. From 2019 to 2010, she was an Assistant Professor at the Department of Electrical and Information Technology, Lund University, Lund, Sweden. Currently, she is an Assistant Professor at KTH Royal Institute of Technology, Stockholm, Sweden. She is the author of more than 60 scientific publications, including 25 journal papers and one book. Her teaching and research interests include electromagnetic scattering and absorption, inverse problems, electromagnetics of stratified media, double-negative metamaterials, mathematical physics, etc. Currently, she is mainly pursuing research as PI within her own project grant "Waveguide theory for artificial materials and plasmonics" awarded by the Swedish Research Council. She is the winner of multiple teaching and research awards, including the L'Oréal-Unesco For Women in Science Sweden Award in 2021.

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

**María Elena De Cos Gómez** received the M.S. and Ph.D. degrees from the Universidad de Cantabria, in 2002 and 2006, respectively. She was involved in nonlinear dynamics: stability and phase-noise analysis of nonlinear circuits, such as oscillators, frequency dividers, self-oscillating mixers, and multiharmonic generators. She was a Researcher Engineer in collaboration with ACORDE S.A from 2004 to 2007. She joined TSC-UNIOVI in 2007. She was an Invited Professor with the I.E.T.R. Rennes, France, in 2011 and 2014, respectively. She was an Associate Editor of the International Journal of Antennas and Propagation. Her research interests are metamaterials design and its applications to antennas and microwave circuits, design of antennas for RFID systems, location techniques, and wireless sensor networks design and applications.

<figure><img src="image_15.png" /></figure>

**Abdullah G. Alharbi** received the B.Sc. degree in electronics and communications engineering from Qassim University, Saudi Arabia, in 2010, the master and PhDs degree in electrical engineering from the University of Missouri Kansas City, USA, in 2014, 2017, respectively. From 2010 to 2012, he was an Electrical Engineer with Saudi Aramco Company. He is currently an Assistant Professor with the Electrical Engineering Department, Jouf University, Saudi Arabia. He authored and co-authored over 45 journal and conference papers and one Springer book. His research interests include digital IC design, Memristor-based circuits, nanoelectronics, Network Routing, Green Communications, and wireless communications. He was a recipient of several awards from Saudi Arabian Cultural Mission in USA, and the University of Missouri Kansas City. He is a member of the Gulf Engineering Union, the IEEE Circuits and Systems Society, the IEEE Young Professionals, the IEEE Signal Processing Society, the IEEE Instrumentation and Measurement Society Membership, and the IEEE Communications Society Membership, and a Professional Member of ACM.
<figure><img src="image_15.png" /></figure>

**Shah Nawaz Burokur** received the Ph.D. degree from the University of Nantes, Nantes, France, in 2005. He is currently an Associate Professor with the Université Paris Nanterre, Ville d'Avray, France, where he carries his research activities at the LEME, a multidisciplinary laboratory in energetics, mechanics, and electromagnetics. His current research interests include the areas of microwave and applications of periodic structures, complex media, metamaterials, metasurfaces, and metagratings, analysis of integrated planar and conformal circuits, antennas, sensors, orbital angular momentum, and holographic imaging. He is also involved in the design of microwave devices based on the powerful concept of transformation optics. He has published one book on transformation-optics-based antennas, six book chapters, and more than 95 articles in scientific journals and holds three patents on metamaterial-based and inspired antennas. Dr. Burokur was a recipient of the Young Scientist Award, presented by the Union Radio-Scientifique Internationale (URSI) Commission B, in 2005. He serves as a reviewer for various journals, including IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, Electronics Letters (IET), Applied Physics Letters, Optics Express, and Scientific Reports. On a national level in France, he is the coordinator of a think tank on new antenna concepts involving metamaterials and metasurfaces in the framework of the GDR Ondes.

<figure><img src="image_16.png" /></figure>

**Sonia Aïssa** received her 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-Energy, Materials and Telecommunications Center (INRS-EMT), University of Quebec, Montreal, QC, Canada, where she is a Full Professor. From 1996 to 1997, she was a Researcher with the Department of Electronics and Communications of Kyoto University, and with the Wireless Systems Laboratories of NTT, Japan. From 1998 to 2000, she was a Research Associate at INRS-EMT. In 2000–2002, while she was an Assistant Professor, she was a Principal Investigator in the major program of personal and mobile communications of the 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 Visiting Invited Professor at Kyoto University, Japan, in 2006, and at Universiti Sains Malaysia, in 2015. Her research interests include the modeling, design and performance analysis of wireless communication systems and networks. Dr. Aïssa is the Founding Chair of the IEEE Women in Engineering Affinity Group in Montreal, 2004–2007; acted as TPC Symposium Chair or Cochair at IEEE ICC '06 '09 '11 '12; Program Cochair at IEEE WCNC 2007; TPC Cochair of IEEE VTC-spring 2013; TPC Symposia Chair of IEEE Globecom 2014; TPC Vice-Chair of IEEE Globecom 2018; and serves as the TPC Chair of IEEE ICC 2021. Her main editorial activities include: Editor, IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, 2004–2012; Associate Editor and Technical Editor, IEEE COMMUNICATIONS MAGAZINE, 2004–2015; Technical Editor, IEEE WIRELESS COMMUNICATIONS MAGAZINE, 2006–2010; and Associate Editor, Wiley Security and Communication Networks Journal, 2007–2012. She currently serves as Area Editor for the IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS. Awards to her credit include the NSERC University Faculty Award in 1999; the Quebec Government FRQNT Strategic Faculty Fellowship in 2001–2006; 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, 2007. She is co-recipient of five IEEE Best Paper Awards and of the 2012 IEICE Best Paper Award; and recipient of NSERC Discovery Accelerator Supplement Award. She served as Distinguished Lecturer of the IEEE Communications Society and Member of its Board of Governors in 2013–2016 and 2014–2016, respectively. Professor Aïssa is a Fellow of the Canadian Academy of Engineering.

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

**Iyad Dayoub** 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 has worked as a System Engineer with Siemens, Middle East; and a Researcher with Alcatel Business Systems, Alcatel, Colombes, Paris. He is currently a Professor of communications engineering. His current research activities at IEMN, Université Polytech- nique Hauts-de-France (UPHF) and INSA H-d-F 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; and an Adjunct Professor with Concordia University, Montreal, from 2010 to 2014. 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_18.png" /></figure>

**Francisco Falcone** received the degree in telecommunication engineering and the Ph.D. degree in communication engineering from the Universidad Pública de Navarra (UPNA), Spain, in 1999 and 2005, respectively. From February 1999 to April 2000, he was the Microwave Commissioning Engineer at Siemens-Italtel, deploying microwave access systems. From May 2000 to December 2008, he was a Radio Access Engineer at Telefónica Móviles, performing radio network planning and optimization tasks in mobile network deployment. In January 2009, as a co-founding member, he has been the Director of Tafco Metawireless, a spin-off company from UPNA, until May 2009. In parallel, he is an Assistant Lecturer with the Electrical and Electronic Engineering Department, UPNA, from February 2003 to May 2009. In June 2009, he becomes an Associate Professor with the EE Department, being the Department Head, from January 2012 to July 2018. From January 2018 to May 2018, he was a Visiting Professor with the Kuwait College of Science and Technology, Kuwait. He is also affiliated with the Institute for Smart Cities (ISC), UPNA, which hosts around 140 researchers. He is currently acting as the Head of the ICT Section. His research interests are related to computational electromagnetics applied to the analysis of complex electromagnetic scenarios, with a focus on the analysis, design, and implementation of heterogeneous wireless networks to enable context-aware environments. He has over 500 contributions in indexed international journals, book chapters, and conference contributions. He has been awarded the CST 2003 and CST 2005 Best Paper Award, the Ph.D. Award from the Colegio Oficial de Ingenieros de Telecomunicación (COIT), in 2006, the Doctoral Award UPNA, 2010, 1st Juan Gomez Penalver Research Award from the Royal Academy of Engineering of Spain, in 2010, the XII Talgo Innovation Award 2012, the IEEE 2014 Best Paper Award, 2014, the ECSA-3 Best Paper Award, 2016, and the ECSA-4 Best Paper Award, 2017.
<figure><img src="image_16.png" /></figure>

**Shah Nawaz Burokur** received the Ph.D. degree from the University of Nantes, Nantes, France, in 2005. He is currently an Associate Professor with the Université Paris Nanterre, Ville d'Avray, France, where he carries his research activities at the LEME, a multidisciplinary laboratory in energetics, mechanics, and electromagnetics. His current research interests include the areas of microwave and applications of periodic structures, complex media, metamaterials, metasurfaces, and metagratings, analysis of integrated planar and conformal circuits, antennas, sensors, orbital angular momentum, and holographic imaging. He is also involved in the design of microwave devices based on the powerful concept of transformation optics. He has published one book on transformation-optics-based antennas, six book chapters, and more than 95 articles in scientific journals and holds three patents on metamaterial-based and inspired antennas. Dr. Burokur was a recipient of the Young Scientist Award, presented by the Union Radio-Scientifique Internationale (URSI) Commission B, in 2005. He serves as a reviewer for various journals, including IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, Electronics Letters (IET), Applied Physics Letters, Optics Express, and Scientific Reports. On a national level in France, he is the coordinator of a think tank on new antenna concepts involving metamaterials and metasurfaces in the framework of the GDR Ondes.

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

**Sonia Aïssa** received her 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-Energy, Materials and Telecommunications Center (INRS-EMT), University of Quebec, Montreal, QC, Canada, where she is a Full Professor. From 1996 to 1997, she was a Researcher with the Department of Electronics and Communications of Kyoto University, and with the Wireless Systems Laboratories of NTT, Japan. From 1998 to 2000, she was a Research Associate at INRS-EMT. In 2000–2002, while she was an Assistant Professor, she was a Principal Investigator in the major program of personal and mobile communications of the 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 Visiting Invited Professor at Kyoto University, Japan, in 2006, and at Universiti Sains Malaysia, in 2015. Her research interests include the modeling, design and performance analysis of wireless communication systems and networks. Dr. Aïssa is the Founding Chair of the IEEE Women in Engineering Affinity Group in Montreal, 2004–2007; acted as TPC Symposium Chair or Cochair at IEEE ICC '06 '09 '11 '12; Program Cochair at IEEE WCNC 2007; TPC Cochair of IEEE VTC-spring 2013; TPC Symposia Chair of IEEE Globecom 2014; TPC Vice-Chair of IEEE Globecom 2018; and serves as the TPC Chair of IEEE ICC 2021. Her main editorial activities include: Editor, IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, 2004–2012; Associate Editor and Technical Editor, IEEE COMMUNICATIONS MAGAZINE, 2004–2015; Technical Editor, IEEE WIRELESS COMMUNICATIONS MAGAZINE, 2006–2010; and Associate Editor, Wiley Security and Communication Networks Journal, 2007–2012. She currently serves as Area Editor for the IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS. Awards to her credit include the NSERC University Faculty Award in 1999; the Quebec Government FRQNT Strategic Faculty Fellowship in 2001–2006; 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, 2007. She is co-recipient of five IEEE Best Paper Awards and of the 2012 IEICE Best Paper Award; and recipient of NSERC Discovery Accelerator Supplement Award. She served as Distinguished Lecturer of the IEEE Communications Society and Member of its Board of Governors in 2013–2016 and 2014–2016, respectively. Professor Aïssa is a Fellow of the Canadian Academy of Engineering.

<figure><img src="image_18.png" /></figure>

**Iyad Dayoub** 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 has worked as a System Engineer with Siemens, Middle East; and a Researcher with Alcatel Business Systems, Alcatel, Colombes, Paris. He is currently a Professor of communications engineering. His current research activities at IEMN, Université Polytech- nique Hauts-de-France (UPHF) and INSA H-d-F 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; and an Adjunct Professor with Concordia University, Montreal, from 2010 to 2014. 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_19.png" /></figure>

**Francisco Falcone** received the degree in telecommunication engineering and the Ph.D. degree in communication engineering from the Universidad Pública de Navarra (UPNA), Spain, in 1999 and 2005, respectively. From February 1999 to April 2000, he was the Microwave Commissioning Engineer at Siemens-Italtel, deploying microwave access systems. From May 2000 to December 2008, he was a Radio Access Engineer at Telefónica Móviles, performing radio network planning and optimization tasks in mobile network deployment. In January 2009, as a co-founding member, he has been the Director of Tafco Metawireless, a spin-off company from UPNA, until May 2009. In parallel, he is an Assistant Lecturer with the Electrical and Electronic Engineering Department, UPNA, from February 2003 to May 2009. In June 2009, he becomes an Associate Professor with the EE Department, being the Department Head, from January 2012 to July 2018. From January 2018 to May 2018, he was a Visiting Professor with the Kuwait College of Science and Technology, Kuwait. He is also affiliated with the Institute for Smart Cities (ISC), UPNA, which hosts around 140 researchers. He is currently acting as the Head of the ICT Section. His research interests are related to computational electromagnetics applied to the analysis of complex electromagnetic scenarios, with a focus on the analysis, design, and implementation of heterogeneous wireless networks to enable context-aware environments. He has over 500 contributions in indexed international journals, book chapters, and conference contributions. He has been awarded the CST 2003 and CST 2005 Best Paper Award, the Ph.D. Award from the Colegio Oficial de Ingenieros de Telecomunicación (COIT), in 2006, the Doctoral Award UPNA, 2010, 1st Juan Gomez Penalver Research Award from the Royal Academy of Engineering of Spain, in 2010, the XII Talgo Innovation Award 2012, the IEEE 2014 Best Paper Award, 2014, the ECSA-3 Best Paper Award, 2016, and the ECSA-4 Best Paper Award, 2017.
<figure><img src="image_19.png" /></figure>

**Ernesto Limiti** is a full professor of Electronics in the Engineering Faculty of the University of Roma Tor Vergata since 2002, after being research and teaching assistant (since 1991) and associate professor (since 1998) in the same University. Ernesto Limiti represents University of Roma Tor Vergata in the governing body of the MECSA (Microwave Engineering Center for Space Applications), an inter-universitary center among several Italian Universities. He has been elected to represent the Industrial Engineering sector in the Academic Senate of the University for the period 2007–2010 and 2010–2013. Ernesto Limiti is actually the president of the Consortium “Advanced research and Engineering for Space”, ARES, formed between the University and two companies. Further, he is actually the president of the Laurea and Laurea Magistrale degrees in Electronic Engineering of the University of Roma Tor Vergata. The research activity of Ernesto Limiti is focused on three main lines, all of them belonging to the microwave and millimetre-wave electronics research area. The first one is related to characterisation and modelling for active and passive microwave and millimetre-wave devices. Regarding active devices, the research line is oriented to the small-signal, noise and large signal modelling. Regarding passive devices, equivalent-circuit models have been developed for interacting discontinuities in microstrip, for typical MMIC passive components (MIM capacitors) and to waveguide/coplanar waveguide transitions analysis and design. For active devices, new methodologies have been developed for the noise characterisation and the subsequent modelling, and equivalent-circuit modelling strategies have been implemented both for small and large-signal operating regimes for GaAs, GaN, SiC, Si, InP MESFET/HEMT devices. The second line is related to design methodologies and characterisation methods for low noise circuits. The main focus is on cryogenic amplifiers and devices. Collaborations are currently ongoing with the major radioastronomy institutes all around Europe within the frame of FP6 and FP7 programmes (RadioNet). He is actively involved in research activities with many research groups, both European and Italian, and he is in tight collaborations with high-tech italian (Selex - SI, Thales Alenia Space, Rheinmetall, Elettronica S.p.A., Space Engineering ...) and foreign (OMMIC, Siemens, UMS, ...) companies. He contributed, as a researcher and/or as unit responsible, to several National (PRIN MIUR, Madess CNR, Agenzia Spaziale Italiana) and international (ESPRIT COSMIC, Manpower, Edge, Special Action MEPI, ESA, EUROPA, Korrigan, RadioNet FP6 and FP7 ...) projects. Regarding teaching activities, He is a member of the committee of the PhD program in Telecommunications and Microelectronics at the University of Roma Tor Vergata, tutoring an average of four PhD candidates per year.
<figure><img src="image_20.png" /></figure>

**Ernesto Limiti** is a full professor of Electronics in the Engineering Faculty of the University of Roma Tor Vergata since 2002, after being research and teaching assistant (since 1991) and associate professor (since 1998) in the same University. Ernesto Limiti represents University of Roma Tor Vergata in the governing body of the MECSA (Microwave Engineering Center for Space Applications), an inter-universitary center among several Italian Universities. He has been elected to represent the Industrial Engineering sector in the Academic Senate of the University for the period 2007–2010 and 2010–2013. Ernesto Limiti is actually the president of the Consortium “Advanced research and Engineering for Space”, ARES, formed between the University and two companies. Further, he is actually the president of the Laurea and Laurea Magistrale degrees in Electronic Engineering of the University of Roma Tor Vergata. The research activity of Ernesto Limiti is focused on three main lines, all of them belonging to the microwave and millimetre-wave electronics research area. The first one is related to characterisation and modelling for active and passive microwave and millimetre-wave devices. Regarding active devices, the research line is oriented to the small-signal, noise and large signal modelling. Regarding passive devices, equivalent-circuit models have been developed for interacting discontinuities in microstrip, for typical MMIC passive components (MIM capacitors) and to waveguide/coplanar waveguide transitions analysis and design. For active devices, new methodologies have been developed for the noise characterisation and the subsequent modelling, and equivalent-circuit modelling strategies have been implemented both for small and large-signal operating regimes for GaAs, GaN, SiC, Si, InP MESFET/HEMT devices. The second line is related to design methodologies and characterisation methods for low noise circuits. The main focus is on cryogenic amplifiers and devices. Collaborations are currently ongoing with the major radioastronomy institutes all around Europe within the frame of FP6 and FP7 programmes (RadioNet). He is actively involved in research activities with many research groups, both European and Italian, and he is in tight collaborations with high-tech italian (Selex - SI, Thales Alenia Space, Rheinmetall, Elettronica S.p.A., Space Engineering ...) and foreign (OMMIC, Siemens, UMS, ...) companies. He contributed, as a researcher and/or as unit responsible, to several National (PRIN MIUR, Madess CNR, Agenzia Spaziale Italiana) and international (ESPRIT COSMIC, Manpower, Edge, Special Action MEPI, ESA, EUROPA, Korrigan, RadioNet FP6 and FP7 ...) projects. Regarding teaching activities, He is a member of the committee of the PhD program in Telecommunications and Microelectronics at the University of Roma Tor Vergata, tutoring an average of four PhD candidates per year.