Developing a compact circularly polarized (CP) antenna with good radiation characteristics for handheld radio frequency identification (RFID) readers is a very challenging task. Many compact CP antennas have been reported in the open literature, but most suffer from critical drawbacks of low gain and/or high back radiation. This paper presents a metasurface (MS) based CP antenna with compact size, high gain, and high front-to-back ratio characteristics. The compact size of the proposed design is achieved by using a 2 × 2 unit-cell MS, while the CP realization is accomplished through a coupling between the MS and a Y-shaped patch as a primary CP source. The final antenna has compact overall dimensions of 0.45λ × 0.45λ × 0.02λ, where λ is the guided wavelength at the center frequency. The operating bandwidth is about 2.0% (2.43–2.48 GHz) and the broadside gain is about 6.3 dBi. Besides, the front-to-back ratio (FBR) defined by the difference gain levels between the forward and backward directions is about 18 dB. Compared with the related compact CP antennas in the literature, the proposed design has the advantages of high gain and high FBR, making it suitable for compact RFID readers. Radio Frequency Identification (RFID) is a wireless communication system consisting of two components: tags and readers . This kiTheoretically, CP radiation can be achieved when the antenna is excited by two orthogonal electric fields with equal amplitude and phase difference of 90°. In –6, multiVarious techniques have been developed to minimize the CP antenna for RFID applications. In , a singlThe motivation of this paper is to design a compact directional CP antenna with high gain and high FBR. To achieve this, the antenna realization is as follows:To achieve compact and directional beam antenna, microstrip patch and MS-based antenna are considered.To achieve high gain, the MS-based antenna is a better option than the patch antenna. This is due to the large radiating aperture of the MS in comparison with the patch.To achieve high FBR or small back radiation, the MS-based antenna has more advantages than the patch antenna. For the patch, the back radiation is caused by the diffraction of the surface wave at the edges of the ground plane. Smaller ground plane results in higher back radiation. In contrast, the electromagnetic waves are confined between the MS layer and the ground plane layer for the MS-based antenna. This contributes to reducing back radiation.Accordingly, the proposed antenna is based on a 2 × 2 unit-cell metasurface (MS) and fed by a Y-shaped patch as a CP source. To demonstrate the feasibility of the proposed concept, measurements are implemented on a fabricated antenna prototype. The measured data show an operating bandwidth (BW) of 2.0% (2.43–2.48 GHz). The antenna with a compact size of 0.45λ x 0.45λ x 0.02λ can achieve a high gain radiation of 6.4 dBi and a high FBR of 18 dB.x- and y-direction are identical, Zx = Zy. Thus, the CP operation can be achieved when a CP source  is used to excite this kind of MS. In the second case, the unit cell has an asymmetric structure. To have CP operation, this kind of MS is commonly excited by a linear source, for example, the vertical polarization in E1 and E2. By controlling the truncated corners, the impedances Z1 and Z2 can be equal in magnitude and 900 out of phase. Consequently, CP realization can be accomplished.The MS-based antenna is one kind of MS application that employed the resonant modes of finite MS. Various MS antennas have been developed for wideband, low profile, or circular polarization applications –24. In tIn this paper, a symmetric MS is utilized. The characteristic mode analysis (CMA) is utilized to predict the modal behaviors and operation characteristics of the MS , 26. To They are identical in modal significance.The current distributions are orthogonal arrangements.The broadside directivities are similar.Note that many MS-based CP antennas have been reported in the literature –30. HoweThe configuration of the proposed compact CP antenna is presented in S11|, AR, and realized gain of these two designs. Around 2.45 GHz, both antennas show good impedance matching with |S11| of less than –10 dB and good CP radiation with an axial ratio (AR) of lower than 3 dB. However, the antenna gain observes a strong difference. For the conventional CP patch antenna, surface wave diffraction at the edges of the ground plane increases the back radiation. For the proposed structure, the electromagnetic waves radiated by the MS at its resonant frequency are confined into the MS through the magnetic coupling effect. When the MS is illuminated by the primary source, the radiated field is spread over a larger radiating aperture than the conventional design. Therefore, the antenna’s gain in the forward direction increases. The back radiation is also further suppressed, leading to high FBR.To demonstrate the effectiveness of the utilized concept, the performances of the proposed MS-based antenna and the conventional CP patch are compared. For a fair comparison, the conventional CP square patch with truncated corners is designed on a Taconic RF-35 substrate with similar overall dimensions to the MS-based antenna. The CP realization of the proposed antenna can be verified based on the simulated current distributions on the CP source and the MS at 2.45 GHz. W0. S11| and AR characteristics for different values of W0. The data indicate that changing W0 significantly affects the operating frequency band. Both impedance matching and AR bands shift upwards when decreasing W0.Since the MS is the primary radiating aperture of the proposed antenna, the operating band is theoretically determined by the size of the unit cell, S11| and AR results against the variation of the patch’s length, l1. As observed, the AR is significantly affected by l1. Meanwhile, the impedance performance is almost stable with the variation of l1.Due to the symmetrical MS, the CP radiation of the proposed antenna is realized by the CP source Y-shaped patch. Thus, the CP operation is optimized through the dimensions of this patch. w2, and the feeding position, G. The effect of w2 and G on |S11| and AR performance is presented in Figs w2 and G have a minor effect on AR performance. The 3-dB AR BW remains unchanged with different values of these parameters. On the other hand, the impact on the matching performance is remarkable. The antenna shows good impedance matching with proper values of w2 and G.The impedance matching is strongly determined by the width, To demonstrate the effectiveness and feasibility of the proposed antenna, a prototype of the antenna was fabricated and measured. The reflection coefficient is measured by a Vector Network Analyzer and the radiation features are implemented in the far-field microwave anechoic chamber.S11| smaller than -10 dB covers a frequency band from 2.30 to 2.57 GHz. x − z and y − z. The measured results show that the proposed antenna has a good radiation pattern, which is quite symmetric around the broadside direction. The FBR is better than 18 dB and the cross-polarization is 20 dB less than the co-polarization.Finally, a comparison of the proposed design with several representative published studies is summarized and tabulated in A compact CP antenna with high gain and high FBR for RFID readers is presented and investigated in this paper. The proposed design is based on the 2 x 2 unit-cell MS and the Y-shaped patch as the primary CP radiating source. The proposed antenna with compact dimensions of 0.45λ x 0.45λ x 0.02λ achieves an operating BW of 2.0% (2.43—2.48 GHz). A high broadside gain of 6.3 dBi and a high FBR of 18 dB are also accomplished. In comparison with other related works, the antenna has the advantages of high gain and high FBR while having similar overall dimensions. The proposed antenna can be a good candidate for compact RFID readers.


This paper proposes a graded effective refractive indexes (GRIN) dielectric lens for 5G applications. The inhomogeneous holes in the dielectric plate are perforated to provide GRIN in the proposed lens. The constructed lens employs a collection of slabs that correspond to the specified graded effective refractive index. The thickness and the whole lens dimensions are optimized based on designing a compact lens with optimum lens antenna performance . A wideband (WB) microstrip patch antenna is designed to be operated over the entire band of interest from 26 GHz to 30.5 GHz. For the 5G mm-wave band of operation, the behavior of the proposed lens along with a microstrip patch antenna is analyzed at 28 GHz for various performance parameters, including impedance matching bandwidth, 3 dB beamwidth, maximum gain, and sidelobe level. It has been observed that the antenna exhibits good performance over the entire band of interest in terms of gain, 3 dB beamwidth, and sidelobe level. The numerical simulation results are validated using two different simulation solvers. The proposed unique and innovative configuration is well-suited for 5G high gain antenna solutions with a low-cost and lightweight antenna structure. The need for high data rates led to the use of millimeter-wave (MM-wave) bands in fifth-generation (5G) mobile systems . The devFor spherical lenses, the beam moving along the main axis is focused on a focal point . So, wheA compatible WB antenna is also necessary for the proposed lens design to operate over a wide impedance bandwidth. In the literature, several techniques have been reported to increase the bandwidth of printed antennas at the millimeter-wave (mm-wave) band. However, such techniques added complexity to the antenna structure. For example, the technique used in  relies oIn , multi-lIn this paper, a widening-band antenna with a GRIN 2D dielectric lens is designed for 5G applications. This lens is made by drilling holes in a flat dielectric in an uneven pattern to obtain an effective refractive index that is similar to that of the Luneburg lens. A compatible WB antenna is designed to work with the designed lens over a wide impedance bandwidth. The antenna dimensions and the thickness and overall dimensions of the lens are optimized with the goal of creating a compact lens antenna with optimal performance .In this work, a microstrip patch antenna is designed to cover a wideband (WB) frequency span to cover the 5G mm-wave standards. For 5G mm-wave applications, the lens must work over a wide frequency range. This means that it needs a WB feeding mechanism. Since the proposed lens design is WB by nature, the feeding mechanism must also be WB-compatible. The optimized integrated lens and patch antenna setup works well over the targeted band, with high gain values and stable performance over the whole band of operation.r = 2.2, and loss tangent tanδ = 0.0009. The PCB board used has dimensions of 12.7 × 52.5 mm2 and a thickness of 0.64 mm. The rectangular patch size is 15.6 × 2.9 mm2 on the top layer. Two circular slots are etched out of 2.5 mm. The bottom layer of the PCB board serves as a reference ground plane for the rectangular patch. The proposed patch antenna is fed via a microstrip line of 1.4 mm width. As shown in To achieve a wide range of impedance, the patch was optimized without any slots by choosing the right patch size. Parametric sweeps are performed to analyze the effect of the width and length of the patch antenna. Both slots are identical and positioned symmetrically around the antenna’s center and they are far away from each other by 4.2 mm. To achieve wideband impedance matching and minimize return loss, the input impedance of the antenna is set to 50 ohms by optimizing the width and length of the feeding microstrip line. As per our findings, the slots created an extra resonant mode at the lower frequency end, which helped in widening the operating bandwidth. The final optimized dimensions resulted in an increased effective bandwidth of the patch in the range of 26–30.5 GHz.z-axis and propagating along the +y-axis, as shown in The antenna port is excited by a Gaussian pulse, polarized along the r = 6.3). For normal incident plane waves on the slab, the relationships between the complex refractive index . The thickness of the unit cell is 1.57 mm (0.1493 λ). The reason for the selection of the value of 1.57 is the commercial availability of Rogers TMM 6 (εrameters  are giveFor passive materials, the real value of When the lens is added to the microstrip patch antenna as shown in  dBi see  to 20 dBcies see  shows hoA comparison of several key metrics of the proposed dielectric slab-based lens antenna with previously published results is shown in In this work, a GRIN dielectric lens has been proposed to meet the high-gain requirements of 5G applications. The proposed design is based on the effective refractive index of a hole-type unit cell. An WB antenna is also designed to be compatible with the lens operation over a wide impedance bandwidth. The proposed integrated patch along with the lens is tested for its performance using a numerical full-wave simulator. The patch-lens system demonstrated a gain of 20 dBi, HPBW of The proposed lens antenna system provides several benefits, such as improved performance, compactness, and low-profile design. It also has the potential to be extended to other frequency bands and applications, making it a versatile and cost-effective solution for wireless communication systems.


These SAR values were observed to be significantly lower than the 1.6 W/Kg threshold set by the Federal Communication Commission (FCC). Moreover, the performance of the antenna was evaluated by simulating various deformation tests.The proposed paper presents a flexible antenna that is capable of operating in several frequency bands, namely 2.45 GHz, 5.8 GHz, and 8 GHz. The first two frequency bands are frequently utilized in industrial, scientific, and medical (ISM) as well as wireless local area network (WLAN) applications, whereas the third frequency band is associated with X-band applications. The antenna, with dimensions of 52 mm × 40 mm (0.79 λ × 0.61 λ), was designed using a 1.8 mm thick flexible kapton polyimide substrate with a permittivity of 3.5. Using CST Studio Suite, full-wave electromagnetic simulations were conducted, and the proposed design achieved a reflection coefficient below −10 dB for the intended frequency bands. Additionally, the proposed antenna achieves an efficiency value of up to 83% and appropriate values of gain in the desired frequency bands. In order to quantify the specific absorption rate (SAR), simulations were conducted by mounting the proposed antenna on a three-layered phantom. The SAR Wearable antennas are gaining popularity in body-centric communication (BCC). The BCC defines three main realms of communication: on-body, off-body, and in-body communication, based on how wireless devices are connected. This categorization aligns with the IEEE 802.15 standardization group [The choice of materials is a crucial factor in designing wearable antennas. Ideally, wearable antennas should be lightweight, low profile, compact, user friendly, and low maintenance. They should also be able to withstand mechanical stresses and deformations. Various materials have been used as antenna substrates due to their favorable electrical, chemical, and mechanical properties for the human body, including textiles , silk 44, nylon Due to the interaction of a wearable antenna with the human body, the gain, efficiency, bandwidth, and driving impedance of the wearable antenna is notably affected. Additionally, a part of the electromagnetic radiation from the antenna penetrates the skin layer and interacts with tissue yielding in heating effect. This is quantified as SAR measured in W/Kg. A low value of SAR is desirable to have minimum side effects as defined by FCC. Various approaches have been adopted by researchers to minimize SAR. Authors in ,11,12 usThe advancement of wireless technology has enabled numerous systems to function across multiple frequency bands. Examples of such systems include satellite navigation, wireless LANs, and ultrawideband (UWB) systems . TherefoThis study, therefore, proposes a multiband wearable antenna that uses flexible kapton polyimide material as a substrate. The antenna is capable of operating in wireless body area networks (WBAN), WLAN, and X-bands. To investigate the specific absorption rate (SAR), we used a three-layer phantom composed of skin, fat, and muscle. Our results show that the achieved SAR values are below the threshold set by the FCC .This paper is organized into several sections. During the past three decades, planar antennas, specifically microstrip antennas, have gained widespread usage. Despite having a narrow bandwidth, researchers have directed their attention towards microstrip patch antennas due to their distinct benefits, such as low manufacturing costs, light weight, and ease of production.The miniaturization of microstrip antennas has emerged as a significant area of interest among antenna designers in recent decades. Typically, the length of a conventional antenna that operates at a given frequency is on the order of half the wavelength of that frequency. However, this length is practically not suitable for several applications such as radio frequency identification (RFID), and the internet of things (IoT) .The miniaturization of antennas with multiband capabilities is an active research area, particularly for wireless devices that require compact and efficient antenna systems. There are several techniques that researchers are exploring to achieve this goal, such as using metamaterials, reconfigurable antennas, and fractal geometries ,29. AddiThe antenna design presented in this study is derived from a typical fork antenna design. The overall design evolution is presented in L, LR, LE, and LF are the lengths of the stubs, horizontal strip, and feed line, respectively, while WL, WR, WE, and WF are their corresponding widths. WS is the spacing between the stubs. Lg represents the length of the ground plane.By changing various parameters of the antenna design, some useful insights can be comprehended. The return loss of the antenna is investigated by changing the length of the ground plane, as depicted in The length of the stubs plays a crucial role in the frequency response of the antenna. Modifying the length of the stubs causes a shift in the center of resonating frequencies, providing frequency-tuning capabilities for the proposed antenna. As depicted in The addition of a horizontal stub to the radiating patch results in the modification of the return loss characteristics of the antenna. This stub was introduced to provide band-pass filtering characteristics to the antenna radiation by creating specific current paths that facilitate efficient radiation in the desired frequency bands. This effect is demonstrated in The dimensions of the feed line are a crucial consideration in antenna design as they impact impedance matching. In our design, a wider feed-line width leads to a lower matching impedance, while a narrower one results in a higher matching impedance. The feed-line width of 2 mm is found to be optimal, as shown in This section presents the simulation results of various performance parameters of the proposed antenna.In order to validate the functionality of the proposed design, the antenna was designed and simulated using the HFSS computational package, which is based on the finite element method (FEM). The comparison of the results is shown in The efficiency and gain of the proposed antenna were computed using both CST and HFSS simulation software. The results, as illustrated in FBR is a measure of the directional performance of an antenna. It describes the ratio of the power radiated in the forward direction compared to the power radiated in the opposite, or backward, direction. A higher FBR ratio indicates that the antenna radiates more power in the desired direction and less power in the opposite direction, which is often desirable in antenna applications. The FBR characteristics of the antenna were simulated using both CST and HFSS, as shown in 11 parameter, which indicates the level of impedance matching that the antenna can achieve. In our case, the antenna demonstrates high impedance matching at 8.0 GHz.In this section, we will discuss the impedance bandwidth offered by the antenna at its resonance bands. A body-worn antenna may undergo different deformations and distortions in real-life scenarios which can affect its performance. Here we present some cases.When an external force is applied to an antenna, it may experience compression, primarily affecting its substrate. To investigate the effects of substrate thickness on antenna properties, we reduced it from 1.8 mm to 1.35 mm and observed a shift in the return loss of the antenna towards the right, as demonstrated in To assess the versatility of the proposed antenna design, we evaluated its performance with substrates other than kapton polyimide. In this experiment, we replaced the substrate with materials of the same thickness, such as nylon, PDMS, and photopaper. Interestingly, we observed that the return loss characteristics deviated to a lesser extent, with resonances almost aligning with the target frequency bands, as illustrated in To evaluate the antenna’s performance in terms of reflection coefficient, gain, and radiation pattern under bending conditions, we developed a three-layered cylindrical phantom using CST. The reflection coefficient of the antenna was analyzed under phantom loading conditions by varying the diameter of the inner cylinder from 50 to 100 mm, simulating changes in the size of the muscle layer. The thickness of the fat layer was kept constant at 2 mm, while the skin layer had a thickness of 1 mm. The tissue layers were assigned frequency-dependent dielectric properties, as specified in In another test, the antenna’s gain was measured at a distance of 3 mm from the skin layer, and the results were plotted as a function of angular distribution in the E-plane, as shown in In body-worn communication, the distance between the antenna and the body can alter the antenna’s radiation-pattern characteristics. To explore this effect, we positioned the antenna at distances of 2, 3, and 5 mm from the skin layer and recorded the corresponding radiation patterns for the operating frequencies, as presented in The performance of the antenna can deteriorate in wet conditions, such as rainy or sweaty environments. To assess its resilience to wet conditions, we added a 1 mm thick layer above the antenna, fully covering its top layer, and filled it with water. We used three different permittivity values of water  to simulate various levels of salt in the water. The results of this test are presented in In practical body-worn communication scenarios, antennas are often placed on garments and exposed to free space. However, if the antenna is covered with body-worn fabrics made of cotton, silk, jeans, etc., its performance can be affected. To study this, a selection of ten body-worn fabrics was chosen, and the variation in return loss was measured with the antenna placed underneath a 1 mm thick layer. The results, shown in 21 parameter. This was accomplished first by configuring a pair of antennas in various positions in free space and then by mounting the antennas on the body.The transmission losses of the proposed wearable antenna can be investigated by evaluating the S21 parameter was then evaluated for three configurations. The results achieved are shown in These positions are defined as front to front, back to back, and side to side with 100 mm of separation. The result for the free-space case is presented in The specific absorption rate (SAR) in W/Kg given by Equation (1) is used to quantify the antenna radiation absorbed by human tissue. A lower SAR value is preferable as per the guidelines set by the FCC.3), respectively [3, 909.4 Kg/m3, and 1060 Kg/m3 respectively. The antenna used in the model was positioned 3 mm away from the skin layer. SAR values were calculated for two different phantom shapes: a flat phantom with dimensions of 180 × 160 × 53 mm3 and a cylindrical phantom with a radius of 90 mm. The tissue layers were assigned frequency-dependent dielectric properties, and the second-order Debye’s model is used for dispersion fitting [Here ectively ,32,33. A fitting . The inp1g are demonstrated in 1g is well below the FCC limit of 1.6 W/Kg.The simulation results obtained for SARThere is rich literature available on the design of new antennas for wearable applications. However, a more suitable comparison for the proposed antenna would be with other antennas that use kapton polyimide as the substrate material. The authors introduced a flexible multiband antenna capable of functioning in ISM, WLAN, and X-bands. The proposed antenna was designed on the flexible substrate of kapton polyimide material  with a size of 52 mm × 40 mm (0.79 λ × 0.61 λ). The reflection coefficient of the antenna is significantly lower than −10 dB for all resonant frequency bands which reflects good impedance-matching characteristics. Appropriate gain values are achieved for the resonance bands with maximum efficiency of 83%. Various simulation tests were conducted to evaluate the antenna’s performance, and it was found that the SAR values were kept to a minimum. Overall, the antenna performed adequately for the target frequency bands.


The simulated and measured results show good agreement, indicating the effectiveness of the UWB-MIMO antenna for wireless communication and portable systems.This study introduces a monopole 4 × 4 Ultra-Wide-Band (UWB) Multiple-Input Multiple-Output (MIMO) antenna system with a novel structure and outstanding performance. The proposed design has triple-notched characteristics due to CSRR etching and a C-shaped curve. The notching occurs in 4.5 GHz, 5.5 GHz, and 8.8 GHz frequencies in the C-band, WLAN band, and satellite network, respectively. Complementary Split-Ring Resonators (CSRR) are etched at the feed line and ground plane, and a C-shaped curve is used to reduce interference between the ultra-wide band and narrowband. The mutual coupling of CSRR enables the MIMO architecture to achieve high isolation and polarisation diversity. With prototype dimensions of (60.4 × 60.4) mm The demand for high data rates in reliable communication has driven advancements in RF and microwave engineering, particularly in the field of wireless communication, which is widely acknowledged as one of the most significant contributions to the technology world. This technological revolution has resulted in the widespread use of digital data. To meet these increasing expectations, Ultra-Wide-Band (UWB) technology was introduced, offering improved communication accuracy, speed, and efficiency of data transmissions. The appeal of UWB technology has grown over the past few decades due to its desirable features such as accuracy, high data rates, and cost-effectiveness. The Federal Communications Commission (FCC) defines UWB within the frequency range of 3.1–10.6 GHz . UWB tecDespite these advancements, challenges remain in terms of antenna size, multiple notching, and additional elements for coupling reduction. In this paper, we present a 4 × 4 crescent-shaped monopole UWB-MIMO antenna system that addresses these size and notching challenges and reduces coupling without the need for additional elements. The proposed system achieves multiple notches for C-band, WLAN, and satellite networks through the etching of Complementary Split-Ring Resonators on the patch elements, ground side, and C-shaped structures. The MIMO antenna system is arranged in an orthogonal configuration to achieve pattern diversity and polarization diversity. The proposed design covers a bandwidth from 2 GHz to 13 GHz. The notching characteristic enables the mitigation of coexisting sub-bands in the UWB region, reducing interference without the complexity of additional circuits. Moreover, the proposed design achieves high isolation in the MIMO system through the mutual coupling of Complementary Split-Ring Resonators, resulting in a miniaturized design. The multitasking of CSRR makes the article novel and differentiable. This miniaturized design is particularly suitable for wireless communication. The multitasking of CSRR is organized in the manuscript as follows: In The UWB design achieves a bandwidth of 2 GHz to 13 GHz by feeding a rectangular patch with a ground plane.Notching characteristics are introduced in the UWB frequency range by placing a CSRR at the feeding point of the patch and another CSRR in the ground plane. Additionally, a curve shape is employed to create a notch for the satellite network band. The CSRR in the feeding line rejects the C-band, while the CSRR in the ground plane rejects the WLAN bands. Both CSRR elements increase the coupling effects and filter high-traffic bands.The 4 × 4 MIMO configuration is achieved by arranging the monopole antennas in an orthogonal configuration, providing pattern diversity and polarization diversity.High isolation within the MIMO system is achieved by utilizing the mutual coupling of CSRR elements at the patch and ground plane, effectively reducing coupling in the MIMO design system.A monopole UWB-MIMO antenna system with triple notching features for C-band, WLAN, and satellite networks is presented. The notching characteristic is achieved by etching Complementary Split-Ring Resonators (CSRR) at the patch elements and ground side, and the third notch is achieved with the C-shape. The 4 × 4 MIMO antenna system is arranged orthogonally to achieve pattern and polarisation diversity. Because of the symmetric positioning of the antenna port components, as well as the mutual coupling of Complementary Split-Ring Resonators, which block the RF signal between the port elements, the MIMO antenna obtained good isolation. In this article, the etching of CSRR achieves both notching qualities and excellent isolation in the MIMO system. The proposed antenna is fabricated on an FR-4 substrate with a dielectric constant of 4.4, loss tangent of 0.02, and a thickness of 1.6 mm. The geometry and dimensions of the monopole, 4 × 4 MIMO, CSRR, and Arch shape or C-shape are illustrated in Interference poses challenges in wireless communication reliability. To address this issue in UWB technology, a notching approach is proposed. The UWB frequency range, designated by the FCC, spans from 3 GHz to 10 GHz. However, WLANs, WiMAX, and satellite links utilize different portions of the radio spectrum, resulting in potential interference when heavily utilized. Interactions between the UWB and occupied narrow bands lead to interference. To mitigate this interference, various parasitic slots are introduced at specific positions, and CSRR elements are incorporated into the final design to reduce interference between the UWB and narrow bands.To enhance performance and mitigate interference in the designated UWB frequency range, a notch in the C-band is introduced. By etching a square-shaped CSRR onto the patch’s feed line, the desired notching characteristic for the C-band is achieved. The CSRR length can be adjusted to fine-tune the notch. Equation  providesFurthermore, when a CSRR is placed at the ground plane, it enables the attainment of a WLAN notch band characteristic. This notching characteristic effectively eliminates crosstalk between the narrow WLAN band and the UWB bands, which experience a high volume of data transfer. The corresponding wavelength of the CSRR, as determined by Equation , is calcSatellite networks often face disruptions in communication rates due to the significant amount of data being transferred among users. By placing a C-shaped (curve-shaped) element in the patch’s center, a notching band can be created for the satellite network. The notch at the satellite network was introduced by the C-shaped curve, which also reduced interference. For the satellite network, the notch frequency was introduced at an estimated arc length of 2.8 mm as shown in The notching characteristics at the C, WLAN, and satellite networks are shown in The simulated and measured results are in good agreement. The simulated gain can go from −8 to 5 dB. Gain improves at in-band frequencies and degrades in notch-frequency ranges. As a result, we may say that the in-band frequency has high gain and low signal suppression, while the notched band has low gain and strong signal suppression. The gain of the antenna is represented in The resonant behavior of the system can be elucidated by examining the surface current distribution on the top and bottom metallic layers, as illustrated in The provided monopole, crescent-shaped, 4 × 4 MIMO antenna exhibits a circular configuration in The inter-antenna correlation is evaluated using the envelope correlation coefficient (ECC) of the UWB MIMO antenna’s diversity parameter. In a MIMO system, low correlation between antennas is desirable, and therefore the ECC (envelope correlation coefficient) value should be close to or at its minimal value, which is zero. In the case of the MIMO antenna system under investigation, it is crucial for the ECC to remain below a certain threshold throughout the entire operating frequency range. Specifically, the ECC should be less than or equal to 0.5 to ensure satisfactory performance and can be calculated using Equation .(2)ECC=The equation establishes a relationship between the Diversity Gain (DG) and envelope correlation coefficient (ECC). When there is a higher degree of correlation among the antennas, the signal power generated by the MIMO system diminishes, leading to reduced reliability of the communication link. As depicted in Figure, the correlation between the antennas is relatively weak, and the design yields the strongest signal. The ECC value is low, while the DG value approaches 10 dB across the entire frequency range. Mean Effective Gain (MEG) represents the power received by an antenna. To ensure good diversity performance, the MEG threshold should be below MEG < 3 dB. Due to the MIMO antenna system’s excellent isolation, a low MEG value can be achieved. The provided Equation  can be uIn this article, a small-sized crescent monopole UWB MIMO antenna is presented, which demonstrates triple notching characteristics at the C-band, WLAN band, and satellite band frequencies of 4.5 GHz, 5.5 GHz, and 8.8 GHz, respectively. The implementation of Complementary Split-Ring Resonators (CSRRs) in the feeding line of the patch for C-band notching and on the ground plane for WLAN band notching, along with a curved C-shaped structure on the top of the patch for satellite network notching, successfully achieves the desired notching properties. The orthogonal positioning of the MIMO antenna system enables high isolation, pattern diversity, and polarization diversity. The diversity parameters, including ECC < 0.5, DG ≥ 10, TARC < 0, and CCl < 0.4 bits/s/Hz, are achieved, indicating improved performance. The incorporation of CSRRs in this study effectively achieves notching and high isolation for the system. The simulated and measured results are in good agreement, validating the proposed monopole crescent-shaped UWB-MIMO antenna. Overall, the presented antenna design, with its small size and desirable characteristics, is well suited for wireless communication, portable system devices, and WLAN systems.


The patch was supported by the FR4 dielectric, which had a permittivity of 4.4 and tan δ = 0.02. A 50 Ω microstrip line fed this antenna. The antenna was designed by the HFSS program, and after that, the simulated results were validated using the measured results. The measurement results confirm that the suggested antenna achieves dual-band frequencies ranging from 2.30 to 4.10 GHz, and from 6.10 GHz to 10.0 GHz, resonating at 2.8, 3.51, 6.53, and 9.37 GHz, respectively, for various applications including commercial, scholarly, and medical applications. Moreover, the antenna’s ability to operate within the frequency range of 3.1–10.6 GHz is in accordance with the FCC guidelines for the use of UWB antennas in breast cancer detection. Over the operational bands, the gain varied between 2 and 9 dB, and an efficiency of 92% was attained. A good agreement between the simulation and the measured results was found.In this paper, a compact dual-wideband fractal antenna is created for Bluetooth, WiMAX, WLAN, C, and X band applications. The proposed antenna consists of a circularly shaped resonator that contains square slots and a ground plane where a gap line is incorporated to increase the gain and bandwidth with a small volume of 40 × 34 × 1.6 mm Globally, wireless communications are expanding rapidly. Given the speed of installation of wireless networks compared to that of building wired infrastructure to cover a specific area, wireless equipment is becoming more affordable and simpler to use ,2. MicroIn response to the need for compact and high-performance antennas, antenna designers have developed a new type of patch antenna that incorporates fractal geometries. Fractal geometries are composed of numerous segments that are precisely alike but with varying size scales. This concept was first introduced in 1983, and antenna designers are now utilizing it to create antennas that outperform traditional patch antennas. By combining fractal shapes with patch antennas, a multiband frequency antenna with high gain can be achieved. The incorporation of capacitive and inductive loads onto the patch surface enhances the antenna’s frequency operation, resulting in a wider bandwidth and a multiband response.The need for wider bandwidth, multiband, and low-profile antennas is rapidly increasing, with both the commercial and military fields requiring multifunctional communication systems that can operate at multiple frequency bands.The literature describes many strategies for creating multiband operations to accommodate developmental requirements ,32,33,34Fractals are recursive in nature ,20. The 3 reduced dimensions.A number of applications, including Wi-Fi, biomedical applications, C band, radar, satellite communication, and wireless computer networks, are covered by the work mentioned by Anita Garhwal and others . In orde3. The reconfigurable antenna is employed by the researchers of  GHz, 1.06  GHz, 0.39  GHz, and 2.09  GHzIn the fourth iteration, the ground was modified by a rectangular slit with a 1 mm thickness, and this modification offers two operating bands,  GHz and  GHz. In the proposed antenna, a ‘‘L” shape is welded on the partial ground that gives two wide bands with impedances of 1.84  GHz and 3.9  GHz, as shown in This patch is applicable to the WLAN, C, and X bands, Bluetooth, and WiMAX. To clarify, the proposed antenna was designed to operate within the frequency ranges typically associated with C and X bands. While the frequency range of 2.30 GHz to 4.10 GHz technically falls under the S-Band, it is sometimes referred to as the lower C-Band (3.7–3.98 GHz). Additionally, the frequency range of 6.10 GHz to 10.0 GHz partially falls within the IEEE-defined C-Band range and is also considered part of the X-Band. Therefore, while the antenna may not cover the entire spectrum of C and X bands, it is compatible with many applications within these frequency ranges. It is concluded that during the antenna’s evolution, the S-parameter curves are improved. The antenna evolution results are presented in The suggested antenna has was the subject of comprehensive study to optimize its design and it was found that its current design offers the best bandwidth performance. Through a parametric study, multiple design options were considered and their effectiveness was tested to arrive at this conclusion. Therefore, the current design appears to be the most efficient and effective option for achieving the desired bandwidth.The proposed fractal antenna has a wideband operation and improved gain. These parameters were reached through a parametric study using HFSS electromagnetic solver high-frequency structure simulator. By changing just one parameter while holding the other parameters constant, the suggested antenna performance was tested.A.Effect of the rayon, RThe antenna patch radius is crucial in determining how much the resonant frequencies vary. B.Effect of the position of Lg1To further improve the performance of the antenna, a slit in the ground plane was inserted. The change in slot position in the partial ground has a significant effect on the wideband operation of the monopole antenna. A decrease in bandwidth is observed when shifting from the suggested value of ‘Lg1’, as shown in C.Effect of the position Lg12 was used to fabricate the suggested fractal antenna to validate the simulation results. The antenna was designed and optimized using the HFSS software 17.2, which is based on the finite element approach (FEM). An FR4 substrate of the optimal size of 40 × 34 mmUsing a vector network analyzer, the suggested antenna reflection coefficient was measured. The proposed prototype antenna covers the range of frequencies from 2.26 to 4.10 GHz and from 6.10 to 10 GHz with an impedance bandwidth of 1.84 and 3.90 GHz successively, and with reflection coefficients of −28.38 dB, −27.62 dB, −21.94 dB, and −17.45 dB, respectively. The suggested antenna matches the bandwidth requirements of several wireless protocols, such as WiMAX , WLAN (2.4–2.484 and 5.15–5.825 GHz), C band (6–8 GHz), and X band (8–10 GHz).An anechoic chamber, such as that seen in The comparison between the measured and simulated radiation efficiency of the antenna is presented in 2 but a small bandwidth. The authors of  GHz and the bandwidth of 3.9 GHz  GHz is for the second band, with four resonant frequencies of 2.8 GHz, 3.51 GHz, 6.53 GHz and 9.37 GHz. In the operational band, this antenna can achieve a radiation efficiency of 92% and a peak gain of 9 dB.To effectively cover WLAN, C band, X band, Wi-Fi, Bluetooth, and WiMAX applications, this work presents the design and fabrication of an innovative ultra-wideband patch antenna. This antenna has compact dimensions of 40 × 34 × 1.6 mm


The operating bandwidth of the proposed UWB antenna extended from 3 GHz to 25 GHz at −6 dB reflection coefficient (VSWR ≤ 3) and extended from both 3.5 to 12 GHz, from 16 up to 22 GHz at −10 dB impedance bandwidth (VSWR ≤ 2). This was used to harvest RF energy from most of the wireless communication bands. In addition, the proposed antenna integrates with the rectifier circuit to create the rectenna system. Moreover, to implement the shunt half-wave rectifier (SHWR) circuit, a planar Ag/ZnO Schottky diode uses a diode area of 1 × 1 mm2. The proposed diode is investigated and designed, and its S-parameter is measured for use in the circuit rectifier design. The proposed rectifier has a total area of 40 × 9 mm2 and operates at different resonant frequencies, namely 3.5 GHz, 6 GHz, 8 GHz, 10 GHz and 18 GHz, with a good agreement between simulation and measurement. The maximum measured output DC voltage of the rectenna circuit is 600 mV with a maximum measured efficiency of 25% at 3.5 GHz, with an input power level of 0 dBm at a rectifier load of 300 Ω.This paper presents a single-substrate microstrip rectenna for dedicated radio frequency energy harvesting applications. The proposed configuration of the rectenna circuit is composed of a clipart moon-shaped cut in order to improve the antenna impedance bandwidth. The curvature of the ground plane is modified with a simple U-shaped slot etched into it to improve the antenna bandwidth by changing the current distribution; therefore, this affects the inductance and capacitance embedded into the ground plane. The linear polarized ultra-wide bandwidth (UWB) antenna is achieved by using 50 Ω microstrip line and build on Roger 3003 substrate with an area of 32 × 31 mm The progress of portable electronic devices in this modern era depends mainly on wireless data transmission technology. This technology has evolved from designing an external antenna to an internal antenna in advanced electronic devices, which requires necessary changes in the shape and performance of the antenna . These a2 and operates in wideband frequency range extending from 3 GHz to 10 GHz and from 16 GHz to 20 GHz. The shunt half-wave rectifier (SHWR) topology shown in In this paper, a complete multiband rectenna is designed and fabricated using an in situ synthesized Ag/ZnO planar Schottky diode. First, a low-profile linear-polarized UWB monopole harvest antenna was designed with the working frequency to cover most wireless communication, with a lower sub-band of 5G and UWB ranging from 2.5 GHz to 25 GHz. A metallic patch radiator in the form of a clipart moon-shaped cut with a semi-circular ground plane along with a U-shaped stub provides good impedance matching. The proposed UWB antenna has a bandwidth of 20 GHz and a peak gain of 5.1 dBi, with omnidirectional characteristics in most of the working bands. Two 3D electromagnetic software were designed and simulated the proposed antenna using computer simulation technology (CST) and Ansys high-frequency structure simulator (HFSS). The genetic algorithm optimization in HFSS version 15 is used to optimize the rectenna dimensions. A planar Schottky diode (PSD) consists of an n-type semiconductor ZnO with an Ag electrode and is synthesized using ADS 2008 (Advanced Design System free version), with both DC and RF performance used for the rectifier design. The synthesized PSD has a current density of 0.1 mA/cmThe design of the proposed monopole antenna is discussed in this section in terms of design procedure, current distribution, fabrication, measured results, and the radiation pattern.3. The antenna could be easily integrated on the same substrate with a rectifier circuit to assist in the RF energy harvesting applications of the mobile device. rε = 3, and thicknesses of h and tan σ, as shown in oW and a length of oL. The ground plane has a rectangular shape with an etched rectangular slot and a curved shape at the top. The antenna’s dimensions are carefully chosen and optimized using both Microwave Studio CST version 2022 and HFSS version 15, and the dimensions values of the designed antenna as marked in The proposed antenna is a compact printed antenna with overall dimensions of 32 × 31 × 1.575 mmoW, oL), which is 50 Ω, and two exclusive non-central circular patches with inner cuts for obtaining the required frequency band-shape slot on the top and a semicircular ground plane with a rectangular truncation on the bottom.This section displays and discusses the design steps of the developed antenna. The detailed structure of the linear polarized UWB monopole antenna is shown in h, w are the hight and width of the transmission line.The effective dielectric constant  and (3), according to the standard formula ,9.rfD1 is the outer dimension of the clipart moon shaped, , as shown in The second step of the design antenna (2) is the etching of small circles, which has an important effect on the impedance bandwidth, as shown in For the third design step, a U-shaped slot is etched under the 50 Ω feed transmission line, as shown in The final design step of the proposed monopole is achieved using a modified ground plane to increase the electrical length by etching a semi-circular defective ground structure in the ground plane. The current distribution is perturbed by inserting an elliptical slot in the radiator, which yields the creation of a novel wideband around 15 GHz and enhances the impedance bandwidth of the final shape to extend from 2.5 GHz to 22 GHz, as shown in The simulated surface current distribution of the proposed antenna at different resonant frequencies is shown in 11| and voltage standing wave ratio (VSWR) of the proposed monopole antenna versus frequency with optimal design are shown in The proposed monopole antenna is a fabricated and manufactured prototype of the proposed UWB antenna as shown in In this section, the far-field radiation patterns and gain at some matched frequencies could be achieved. The photo of the measure radiation pattern setup is custom-made in the electronics Research Institute, Microstrip Lab, and shown in The comparison between simulation and measurement of the gain and radiation efficiency of the proposed UWB antenna is shown in The antenna radiation efficiency is measured over the operating bands using the Wheeler cap method ,15 at th2. The proposed diode consists of Ag/ZnO layers supported on a copper layer with the scotch barrier at the Ag/ZnO junction. In this paper, a ZnO n-type semiconductor with an Ag electrode is used to implement PSD for multiband operation with total dimensions of 1 × 1 mm2.The Schottky diode consists of one layer of a p-type or n-type semiconductor positioned between two metal sides: one represents the electrode which allows charge injection in one direction, while it is blocked in the other . Among t2. A wideband transmission line (WBTL) is first designed using the ratio of the width to length of the WBTL equal to 3 mm/20 mm with 0.25 mm separation and it is implemented on Rogers 3003 substrate. The measured WBTL reflection coefficient is less than −20 dBm in the frequency range from 2 GHz to 25 GHz; the proposed diode is then applied on it to investigate the performance of the fabricated diode.The PSD is first fabricated on the same substrate as Rogers (RO3003) and characterized using the design of the rectifier circuit. The device is implemented using nano electronics fabrication, similar to ZnO n-type semiconductor nanoparticle ink  and commercial silver paste Ag electrode with size 1 × 1 mm11| measured with one side of the WBTL is connected to the ground to obtain the device S-parameter shunt connection performance. To investigate the PSD diode performance, its I/V characteristics are measured using the Keithely 4200 SCS (semiconductor characterization system), as shown in 2, and a maximum current density 0.1 mA/cm2 with an IOn/IOff current ratio equal to four. This is due to the usage of commercial grades of Ag and copper tape; applying a scientific-grade material can improve diode performance. The S-parameter performance of the diode is shown in 2, as shown in C1 = C2 = 2pF, whereas the resistive load could be changed with no effect on the S-parameter.A single matching circuit is designed for multiband operation; this reduces the efficiency compared with the single-frequency matching circuit, but shows a good impact of reduction on the rectifier area. To determine the optimum load used of the rectifier operation, simulations for RF-DC conversion are carried out at different load resistances; then, the RF input signal is applied to the rectifier at different operation frequencies of 3.5 GHz, 6 GHz, 10 GHz, and 18 GHz. The output DC voltage and conversion efficiency simulations for three resistive load values, 300 Ω, 1 kΩ, and 5 kΩ, are shown in dcV is measured. dcV is measured and then used in Equations (4) and (5) to calculate the DC output power DCP and efficiency η as:loadR = 300 Ω and inP represents the RF input power.A load of 300 Ω is used for rectifier implementation, and the rectifier is connected to the antenna and complete rectenna DC output voltage inP) sweep from −10 dBm to 10 dBm is applied to the horn and electromagnetic power is radiated to antenna. Output DC from the rectifier is measured using an AVO meter. An input power (2. A shunt half-wave rectifier with an Ag/ZnO PSD is proposed. The PSD has a current density of 0.1 mA/cm2 and has a wideband frequency extending from 3 to 10 GHz and from 16 to 20 GHz, with an area of 1 × 1 mm2; the measured S-parameters of the PSD are used to design the SHWR rectifier. The proposed multiband rectifier operates at 3.5 GHz, 6 GHz, 8 GHz, 10 GHz, and 18 GHz and has an O/P DC voltage of 400 mV at 0 dBm I/P RF signal, with a total area of 40 × 9 mm2. The complete rectenna has an O/P DC voltage of 250 mV and 0.21 mW DC power at zero dBm received signal, which can be used for powered portable electronics and tiny sensors with a maximum efficiency of 25% at 3.5 GHz. Aside from its simple fabrication technique and multiband of operation, it is a good choice for RF energy-harvesting modules at different wireless communication applications for battery-less electronics applications.This paper presented the design and implementation of multiband rectenna for RF energy harvesting applications. An UWB moon-shaped cut-printed monopole antenna was designed with a defected curvature ground plane and U-shaped slot to improve the antenna bandwidth by changing the inductance and capacitance in the ground plane. The proposed UWB antenna is fed by a 50 Ω transmission line and built on RO 3003 substrate with an area of 32 × 31 mm


A wideband dual-reflector 3D-printed antenna is proposed to operate in the mm-Wave band. The design is based on a Cassegrain reflector optics but including a dielectric piece for merging the feeding system and the support structure of the subreflector. The operational principle of this antenna is presented, as well as the design parameters. Then, a prototype to operate at Ka-band is manufactured combining a 3D-printed technique using PLA as printable material and a spray to coating the antenna, providing a low-cost affordable solution. The different pieces of the antenna are evaluated, and the antenna is also measured in a spherical compact range. An excellent agreement between simulations and measurements is obtained, resulting in a  However, the boost of wireless communications has been reached with the development of the next generation of mobile communications, namely the current fifth generation (5G) or the so-called beyond 5G (B5G) and 6G. These generations demand high energy efficiencies together with high data rate systems to enhance the capacity of communications. Those new specifications require to use large bandwidth or multiple bands, and these three generations intend to use frequencies within the (sub)millimeter band of the spectrum. Several regions, such as Europe, EEUU, or Japan have booked bands centered at 28 and 39 GHz (FR2), or even plan to work in higher frequencies up to 200 GHz, to provide high-speed wireless cellular networks3.Wireless technologies have increased their interest throughout the last decade owing to applications such as microwave imaging (MWI)5. These constellations use small platforms, small-geo satellites for geostationary orbits or mega-constellations of CubeSat7 in the lower orbit to provide the telecommunication services. As it is well-known space industry demand the highest performance on their devices, pushing the research community to do their best. Thus, spaceborne antennas are characterized for being always on the edge of technology, reaching the tightest performance in terms of beam shaping, efficiency, or reliability8.In this line, space industry has increased their interest in the development of new solutions based on Low and Medium Earth Orbit satellite constellations to provide 5G global broadband telecommunication service10. In its classical configuration the reflector is illuminated by a primary feed, which needs a feed chain system . However, there are more complex configurations based on dual-reflector topologies, being the most popular the Cassegrain. In this case, the primary feed illuminates the subreflector surface, whose reflection provides the incident field onto the main reflector. This configuration typically improves the gain or radiation efficiency, as well as the radiation performance, such as sidelobe level (SLL), ohmic losses or the noise figure when are compared with single reflectors. The main drawback is the need of supporting structures to hold the subreflector, which increase the blockage losses11. Different structures have been proposed in the literature to obtain self-supported subreflectors, being the most common approach the hat-feed reflectors14. These solutions provide a good trade-off between compact structures and aperture efficiency due to the corrugations used in the metallic hat.Satellite communications usually require high-gain antennas, being parabolic reflector the most popular solution15.Additive manufacturing (AM) has brought a revolution to many engineering areas, having a deep impact on industry. AM should not be only about changing manufacturing process or taking the advantages of new materials. AM is a matter of enabling powerful new concepts or designs which are not affordable by traditional manufacturing, and it can have a noticeable impact on spaceborne antennas. It is applicable to several materials, ranging from polymers or composites to ceramics, or even metals. It fits well for reaching complex design in single-piece (monolithic) structures, which decrease the weight and volume of devices18, namely, to manufacture a dielectric skeleton of the reflector surface using any of the classical 3D techniques, such as SLA or FDM. Then, the skeleton is metallized using vacuum metallization, conductive coating, or electroplating. A further step was introduced in19, which presents a dual-reflector antenna with a novel dielectric self-supported subreflector in Cassegrain configuration. This work proposes an innovative technique to avoid supporting struts taking AM as key factor to manufacture the antenna.AM has been also applied to reflector antennasThis work presents a dual-reflector Cassegrain at Ka-band as a broadband high gain solution to operate between The proposed Cassegrain antenna is made up of a main parabolic reflector, a hyperbolic structure that behaves as a subreflector, and a primary feed as Fig. 11.On this basis, the feed of the proposed antenna is based on a standard waveguide WR28 that works as a feed for the antenna as well as supporting structure. It is connected to a Dielectric Rectangular Waveguide (DRW) by an H-plane linear taper. The DRW is gradually widened in a conical shape as Fig. 19. Two important factors must be underlined here. First, the focal point The details of the design process of each element of the self-supported primary feed and subreflector are further described in20, so that the length 21. For the shortest length the DRW plus taper is matched within the whole desired band, nearly reaching and The resulting antenna optics achieves a well-focused reflector and subreflector, whose outgoing rays are parallel at the antenna aperture despite the dielectric used for propagating the wave. The design parameters, depicted in Fig. The antenna is designed at the lower frequency 20 is used for the DRW, cone, and main paraboloid. The metallic surfaces, paraboloid main reflector, hyperboloid subreflector and feeding waveguide are defined as PEC. The planes The antenna optics of Table The effect of the roughness has been also evaluated in full-wave simulations. To do so, two new simulations are carried out considering 22, was applied to the hyperbolic (subreflector) and parabolic (main reflector) surfaces to create a reflecting surface. The manufactured and assembled antenna, after coating it, is shown in Fig. The antenna defined by the geometry of Table 21.The manufactured wideband antenna was measured at facilities of the University of Oviedo to evaluate its performance and compare the results with the full-wave simulations. First, the return loss of the antenna was analyzed over Ka-band. The results of Fig. Then, the antenna was measured in the anechoic chamber to get its radiation pattern, Fig. First, the antenna performance is evaluated at the centered frequencies of the 5G-FR2 band, In addition to dual-band performance, an overall good agreement between simulations and measurements is obtained, and the antenna exhibits stability in beamwidth, gain and pointing direction for the entire Ka-band, see Fig. The 3D radiation pattern has been also measured in the anechoic chamber from The antenna gain has been simulated considering lossy and lossless conditions for PLA to evaluate the impact of using this material at mm-Wave frequencies. However, the metallic surfaces are defined as PEC and therefore this effect is not considered in the simulations. As shown in Fig. A 3D-printed wideband antenna operating within Ka-band covering the FR2 band is proposed in this work to exploit the increasing interest in mm-Wave communications. A technique based on Cassegrain optics is applied to design the antenna at


The proposed design characterizes an impedance bandwidth starting from 2.8 to 12.1 GHz (124.1%). Each of the four elements of the proposed MIMO antenna configuration consists of a monopole antenna with PG  that has a slot at its center. The corner of each patch (radiator) and ground slot are rounded for impedance matching. Each unit cell is in an orthogonal orientation, forming a quad-port MIMO antenna system. For reference, the partial ground of each unit cell is connected meticulously with the others. The simulated results of the proposed quad-port MIMO antenna design were configured and validated by fabrication and testing. The proposed Quad-port MIMO design has a 6.57 dBi peak gain and 97% radiation efficiency. The proposed design has good isolation below 15 dB in the lower frequency range and below 20 dB in the higher frequency range. The design has a measured ECC (Envelop Correlation Co-efficient) of 0.03 and DG (Diversity Gain) of 10 dB. The value of TARC  over the entire operating band is less than 10 dB. Moreover, the design maintained CCL (Channel Capacity Loss) < 0.4 bits/sec/Hz and MEG (Mean Effective Gain) < 3 dB. Based on the obtained results, the proposed design is suitable for the intended high data rate UWB wireless communication portable devices.In this article, a compact 4-port UWB (Ultra-Wide Band) MIMO (Multiple Input Multiple Output) antenna is proposed. A low profile FR-4 substrate is used as a dielectric material with the dimensions of 58 × 58 mm The wireless communication industry is currently experiencing a tremendous growth in the area of Radio Frequency (RF) and antenna design. Researchers are trying to find new ways to design antennas with high data rates and low power consumption. Ultra-wideband (UWB) MIMO (Multiple Input Multiple Output) antenna design is an ultimate choice for short-range wireless applications ,2,3. For2 dimensions. The operating bandwidth of the design is 3.2–12 GHz with 4 dBi peak gain. The mutual impedance among the antenna elements is 22 dB without using any decoupling mechanism. Although the design is compact with good performance, the drawback is its complex geometry, which makes the fabrication and testing difficult. A compact 4-port slotted MIMO antenna of rectangular shape is reported in [2. The operating bands of the reported design are 3.25–3.75 GHz, 5.08–5.90 GHz, and 7.06–7.95 GHz with a gain varying between 1.4 and 4.6 dBi. Isolation of 22 dB and TARC > −10 dB is achieved using 4-staircase-shaped decoupling techniques. The overall design has a complex structure and decoupling technique. In [2. A Y-shaped slot is introduced at the bottom of the MIMO antenna for isolation enhancement, which results in 15 dB isolation at lower frequencies of the UWB spectrum. A gain varying between 2.55 and 3.58 dBi is achieved over the operating band. The reported design has two elements with complex structures and low port isolation. Another 2-port UWB-MIMO antenna of rectangular shape using CSRR (complementary Split Ring resonator) is reported in [3 with an overall gain between 2 and 5.2 dBi, and 15 dB isolation among ports is achieved. The reported antenna has a band notched with a T-shaped stub in the ground plane. The results of the proposed design show that the designed antenna is not in the UWB frequency range. Moreover, the design exhibits low isolation, which reduces its usefulness for real-time applications. In [3, achieving a 70% efficiency and 15 dB port isolation. The drawback of the reported design is low isolation and a disconnected ground. A planner 4-port UWB-MIMO antenna using a 3 × 3 EBG (Electromagnetic Band Gap) array structure is reported in [3. The reported design resonates at 3–16.2 GHz with a sharp band notch at 4.6 GHz. This design has 17.5 dB isolation with larger dimensions and a disconnected ground. In [2. The antenna has an overall bandwidth of 2.2–6.28 GHz, covering LTE (2.2–3.8 GHz), Bluetooth (2.4 GHz), WLAN , WiMAX (2.3–5.7 GHz), and ISM (2.4/5.2/5.8) bands. However, the reported design has achieved a 4 dBi peak gain and 14 dB port isolation. Larger dimensions and low port isolation reduce the usefulness of the reported design. A 2-port UWB-MIMO antenna with elliptical-shaped radiators is reported in [2. The proposed system operates at 3.1–10.6 GHz with low impedance matching and port isolation. Each of the aforementioned designs makes a compromise between size and achieved results. Some of them are compact in size with low gain and port isolation. Some designs show relatively high performance but are larger in size with complex decoupling techniques, which reduces their usefulness.In , a step-orted in . The antique. In , a 2-pororted in . This anions. In , a quad-orted in . The totound. In , a 4-eleorted in . The rep(i)MIMO antennas are helpful in enhancing the data rate without the provision of additional bandwidth.(ii)Achieving high performance, high port isolation, and a compact size without additional structure with the design is challenging.From the literature review, we obtained the following useful information:The proposed design has a partial ground with a rectangular slot to offer a wide band with better impedance matching.Cross-shaped strips above the substrate are symmetrically added among the MIMO elements to enhance the ports’ isolation and impedance bandwidth.The designed antenna is very compact in term of electrical and physical size.A high efficiency and Gain is achieved over the entire operating band.High isolation has been maintained over the operating band with a novel decoupling technique.The scientific novelty of the proposed design is driven by the design simplicity and achieved results. The proposed design has a simple structure without the incorporation of complex techniques or additional structures like metamaterials or metallic vias for the decoupling, bandwidth, and gain enhancement. In this work, a compact four-port UWB-MIMO antenna operating at 2.8–12 GHz is reported. The proposed design has a connected ground and a simple decoupling technique. The main contributions of the proposed work are as follows:The rest of the article is structured as follows: The suggested antenna design is discussed in S and LS are the width and length of the substrate, respectively. LP and WP are the length and width of the single patch element, respectively. LF and WF are the length and width of the single antenna element feedline, respectively. Notably, all MPAs have a uniform featured gap of 19 mm. L and SW. To provide the same common reference for the input signal with effective isolation performance between MIMO antenna elements, a whirligig structure was introduced meticulously at the bottom of the substrate. For port isolation, bandwidth enhancement, and mutual impedance matching improvement, two hook-shaped strips of 1 mm width were uniformly placed between the MIMO elements. The dimensions of the hook-shaped structure are characterized by LU and WU. This technique extends the operating band to a lower frequency range, thus making the design compact by reducing the electrical length. All numerical simulations were carried out using CST (Computer Simulation Technology) Microwave Studio 2021. The proposed 4-port UWB-MIMO antenna incorporates four single-unit cell microstrip patch antennas (MPA). As depicted in The detailed evaluation steps of the proposed design are shown in The proposed design starts with the design of a single-antenna element. The unit cell design is based on certain important parameters, which include the variation in the ground plane slot length and width, impact of rounding the radiator and ground slot edges, and impact of the cross hook-shaped strips. Variation in these parameters highly influences the impedance matching and operating bandwidth. A detailed parametric study is discussed below.L” improves the impedance matching and enhances the operating bandwidth. At the ground length of 14 mm, the maximum operating band is achieved. At this length, not only is the bandwidth at its maximum, but there is good impedance matching of the whole operating band. Further increasing the ground length deteriorates the impedance matching at higher frequencies, thus reducing the overall bandwidth.The parametric study starts by analyzing the impact of the ground plane on the reflection coefficients, as depicted in W” improves the impedance matching and operating bandwidth. At the value of 4 mm, the design attains a good impedance matching and bandwidth. Further increasing the ground slot width reduces the impedance matching; thus, a slot width of 4 mm is finally selected. The impact of slot length “SL” on the reflection coefficients is seen in L) has an impact on the operating band and impedance matching. By increasing slot length, the impedance bandwidth improves throughout the operating band. A slot length of 5 mm is finalized. Any further increase in the slot length reduces the operating bandwidth and decreases the impedance matching.The width of the ground slot is another important parameter that impacts the operating bandwidth and impedance matching. Rounding the edges of the radiator and ground slot also impacts the impedance matching. Gradually increasing the curve increases the impedance matching. With the curve of a 2 mm radius, a good impedance matching for an overall operating band is achieved, as shown in The cross hook-shaped strips were placed symmetrically among the MIMO antenna elements. The length and width of the cross hook-shaped patches impact both the reflection coefficients and mutual impedances. The final simulation and measurement results of the proposed design are presented in this section. These results provide details of the proposed design performance. The main performance parameters are reflection coefficients, isolation co-efficient, current distribution, far-field radiation pattern, and gain of the design.With the help of the CST Microwaves Studio 2021 software, the proposed UWB-MIMO system was meticulously designed, simulated, and analyzed. To accurately describe and evaluate the antenna system’s performance, this robust electromagnetic tool was utilized. In order to verify the accuracy of the simulated results, the design was fabricated and experimental measurements were conducted. For the accurate measurement of the antenna far-field pattern, an anechoic chamber was utilized, which eliminates external reflections and interference. A Vector Network Analyzer (VNA) was used to carry out these measurements, which allows for the accurate characterization of the key parameters, including reflection coefficient and gain. During the testing process of the suggested design, Port-1 was connected with input, are other ports were terminated with 50 Ω impedance to ensure proper impedance matching, allowing for reliable and consistent measurements.As indicated in The current distribution provides insight into behavior and operating modes at the target resonance frequencies of the proposed antenna. XY-plane) and magnetic (H) (XZ-plane) far-field radiation patterns at the achieved resonance frequencies are shown in The proposed design’s electrical (E) , diversity gain (DG), channel capacity loss (CCL), mean effective gain (MEG), and total active reflection coefficient (TARC) were analyzed to evaluate the MIMO and diversity performance of the proposed antenna.θP and φP are the angular power in elevation and azimuth directions, respectively [ECC measures the correlation or isolation between the various branches of communication; the ECC is a key parameter in MIMO antenna systems. In this study, the suggested MIMO antenna’s far-field patterns were used to compute the ECC, which is represented using Equation (1) . In Equaectively . A suitaectively . The simAnother key variable used to compare the usefulness of MIMO antenna systems to single-antenna systems is diversity gain (DG). Equation (2) is used to calculate DG and measures the strategies to increase the signal quality . In EquaChanel Capacity Loss (CCL) is another vital MIMO antenna parameter. The effectiveness of the suggested design throughput can be demonstrated with the help of CCL. The better the data transfer, the lower the CCL value should be. A desirable CCL value for data transmission is 0.4 bits/s/Hz . EquatioAnother key component in the design of MIMO antennas is mean effective gain (MEG). It is the amount of power received when comparing diversity antennas to isotropic antennas. It demonstrates how the antenna can absorb electromagnetic radiation in a multi-path environment. Using Equations (6) and (7), MEG is calculated . In EquaikS) and phase angle (ɵ).Another key factor of the MIMO antenna is the Total Active Reflection Coefficient (TARC). It is the proportion between the square root of the total power incident and reflected. It is useful in finding out the operational bandwidth of MIMO antenna systems. For a MIMO antenna system, the TARC is determined using Equation (8). In Equation (8), the TARC is determined using the S-parameters (A MIMO antenna system’s TARC should be below −10 dB. Therefore, any TARC value below −10 dB is seen to be optimal for improved communication. Group delay is another important parameter of UWB antenna design performance. It describes the amount of delay introduced in frequencies while passing through different components of the devices. A large group delay shows the distortion in the transmitted signal. The group delay of the proposed design was determined in two orientations. A novel 4-port UWB-MIMO antenna was successfully designed, simulated, and fabricated. The suggested UWB-MIMO antenna system demonstrates outstanding performance for wireless applications. The antenna elements were arranged symmetrically in an orthogonal manner for good diversity polarization. Two different techniques were introduced to enhance the performance. For the provision of the same reference signal, a whirligig structure was introduced in the ground plane. The impedance matching at lower frequencies and port isolation were effectively enhanced by incorporating an inverted cross hook-shaped strip on the top of a substrate. The UWB-MIMO design demonstrates excellent diversity parameters, including a maximum DG of 10 dB, an ECC of 0.003, TARC less than −10 db, MEG better than −3 Db, CCL less than 0.4 bits/s/Hz, and over 20 dB port isolation. The fabricated prototype measurements are in close agreement with the simulated results, verifying the robustness and viability of the UWB-MIMO antenna design.


The antenna with a total dimension of 80 mm × 50 mm × 0.6 mm (0.12In this study, a novel reconfigurable triple-band monopole antenna for LoRa IoT applications is fabricated on an FR-4 substrate. The proposed antenna is designed to function at three distinct LoRa frequency bands: 433 MHz, 868 MHz, and 915 MHz covering the LoRa bands in Europe, America, and Asia. The antenna is reconfigurable by using a PIN diode switching mechanism, which allows for the selection of the desired operating frequency band based on the state of the diodes. The antenna is designed using CST MWS The Internet of Things (IoT) is a fast-growing network that globally interconnects objects, supporting various input/output devices, actuators, and sensors for real-time data collection, control, analysis, and sharing using standard communication protocols. The IoT has had a great influence on our daily lives and has evolved from machine-to-machine communication to connecting people, objects, data, and services. It is considered a key enabler of Cyberphysical Systems (CPSs), which use IoT to link the physical and virtual worlds .One of the critical challenges in IoT is developing communication protocols that meet the energy efficiency, wide signal coverage, energy conservation, affordability, and prolonged battery duration requirements of IoT devices. Low-Power Wide-Area Network (LPWAN) technology is a solution that meets these requirements and has LoRa as one of its major contenders. LoRa is a patented radio modulation technology that utilizes unlicensed frequency bands below 1 GHz and is suitable for IoT applications because of its availability globally and lower cost. The aim of LoRa is to enable IoT devices to communicate over long ranges with improved network capacity, secured data transmission, reduced device cost, and low power consumption ,3,4,5,6.Owing to regulatory requirements, the operating frequency bands for LoRa in the ISM bands differ according to regions and countries. For example, within the band of 410–441 MHz in China, about 32 channels were defined for LoRa applications . In EuroRobust and sophisticated communication protocols and efficient hardware are vital to accomplishing an efficient communication network. Communication devices use antennas to transmit and receive signals; therefore, an antenna is an integral part of LoRa IoT devices ,12,13,14Conventional LoRa modules are equipped with a single whip antenna operating at a fixed frequency. On the other hand, modern IoT devices communicate over multiple frequency bands. The device will be cumbersome if several single-frequency resonant antennas are used. Hence, there is a need for a single multiband antenna for IoT communication to extend network capacity . It shouReconfigurable antennas are a better choice to overcome these challenges. The concept of reconfigurability in antenna design refers to its capability to adjust its characteristics, such as polarization, radiation pattern or resonant frequency. A reconfigurable frequency antenna can switch its operating frequency to a chosen band. Therefore, the frequency spectrum can be efficiently utilized ,18.The modern printed circuit technology enables easy manufacture of Microstrip Patch Antennas (MPAs), which are also lightweight and mechanically robust. Moreover, these antennas can be integrated with both planar and non-planar surfaces ,20,21. IThere have been a number of documented antenna designs ,40,41,42In , a minia3 using HFSS and Grey Wolf Optimizer (GWO).In , an FR-43 designed to support three antennas operating at four frequency bands was presented in [An IoT terminal with a dimension of 300 × 30 × 0.8 mmented in . The ter2 and is switched electronically to achieve four patterns. With a single-slot radiator, the antenna achieved a peak gain greater than 0.5 dB, whereas a gain of 1.6 dB was achieved in the monopole configuration. This antenna has compact and reconfigurable characteristics but is fixed to only one LoRa frequency.A reconfigurable pattern antenna at 868 MHz was reported in . The ant2. It has covered all the LoRa bands in the sub-1 GHz: 915 MHz, 868 MHz, and 433 MHz, with a peak gain of 2.56 dB. This antenna is compact but cannot be tuned to suppress or select a particular LoRa frequency band.A compact wideband double leaf-shaped MPA was reported in . The antThis work presents a compact, novel, triple-band frequency reconfigurable monopole antenna for LoRa IoT applications on commercially available and cheaper FR-4 material. The antenna with a dimension of 80 mm × 50 mm × 0.6 mm can be tuned using two (2) RF (Radio Frequency) PIN diodes (D1 and D2) placed strategically in the branches of the antenna. Switching these diodes enables the antenna to operate at 915 MHz, 868 MHz, and 433 MHz, depending on the state of the diodes. These covered the LoRa frequencies across the globe. Meandered radiating monopoles and partial ground plane are employed to achieve compact size and impedance matching of the antenna. To the best of our knowledge, this is the first compact reconfigurable antenna that covered all the LoRa frequencies.The subsequent sections of this paper have been organized as follows: The endless demand for compact and low-cost wireless IoT systems has increased the necessity for miniaturized, compact, and portable antennas. Such compact antennas should fit easily into every small space for IoT applications. Here, the proposed antenna’s methodology, basic structure, theory, design, and reconfiguration mechanism are presented.The geometry of the proposed antenna is shown in ® software environment. The detailed dimensions of the antenna parameters in millimetres are presented in c = speed of light in vacuum and To make the antenna integrable in emerging IoT devices, standard credit card dimensions of 85.6 mm × 53.98 mm are targeted to be the size of the proposed antenna. The type and characteristics of the substrate were chosen to make the antenna planar, cheaper, and easy to fabricate. The substrate has ented in ,44. A moBy folding the monopole conductors back and forth to form a meandered-line antenna as shown in branches 1 and 2 of Frequency reconfigurability in an antenna refers to the ability to alter the path that current follows on the antenna’s surface, thereby allowing for a shift in resonance to the desired frequency band. Instead of using multiple antennas operating at different frequencies, a reconfigurable frequency antenna can achieve the same function and simultaneously reduce cost and save space. Various techniques and methods are used to achieve frequency reconfiguration, including switches or slots on an antenna’s radiating elements. Electronic switches used for reconfiguration in antenna include Field-Effect-Transistors (FET), Varactor diodes, Micro-Electromechanical Systems (MEMS), PIN diodes, etc. PIN diodes have received much attention for use as a switch in antenna due to their low cost, moderate isolation, less complicated biasing circuitry, and ease of integration with the antenna elements ,46. In tIt is evident from This section presents a discussion and analysis of the performance of the proposed antenna, with a focus on the return loss , triple band reconfigurable monopole antenna for LoRa IoT applications was presented. By utilizing two PIN diodes (D1 and D2) to switch the antenna to different modes, resonance at 433 MHz, 868 MHz, and 915 MHz was achieved, depending on the states of the diodes. When D1 is turned ON, and D2 is turned OFF, the antenna operates in the 433 MHz band, which is the designated frequency for LoRa in Europe. Conversely, when D1 is turned OFF, and D2 is turned ON, the antenna operates in the 868 MHz band, which is also used in Europe for LoRa applications. When both diodes are turned ON, the antenna operates in the 915 MHz band, the designated frequency band for LoRa in North America and some Asian countries. To keep the cost of the antenna low for LoRa IoT applications, the substrate and reconfiguration mechanisms chosen were cost-effective. Additionally, the antenna was miniaturized to have a dimension smaller than the size of a standard “credit card”. With a peak gain of 2 dBi and a radiation efficiency above 90%, this proposed antenna is novel in terms of size and performance for LoRa IoT applications. The antenna was prototyped and tested to validate its performance, and the results of measurements are in good agreement with those of simulation.In this paper, a novel compact (80 × 50 × 0.6 mm


In this work, a highly miniaturized microstrip antenna array based on two elements is proposed for multiple inputs multiple outputs (MIMO) application systems at sub-6 GHz frequency bands. The antenna is structured from a meander line in conjugate with an interdigital capacitor when excited through the monopole basic antenna. The proposed antenna elements are separated with a Minkowski factor-shaped metamaterial (MTM) column to achieve a separation distance (D) of 0.08λ at 3 GHz when printed on an FR-4 substrate. Later on, the antenna performance in terms of bandwidth and gain is controlled using a photonic process based on optical active switches based on light-dependent resistances (LDR). Therefore, the reconfiguration complexity with such a technique can be eliminated significantly without the need for a biasing circuit. The antenna design was conducted through several parametric studies to arrive at the optimal design that realizes the frequency bandwidth between 3 and 5.5 GHz with a maximum gain of about 4.5 dBi when all LDR terminals are off. For a wireless channel performance study-based massive MIMO environment, the proposed antenna is suitable to be configured in arrays of 64 × 64 elements. From this study, it was found the maximum bit error rate (BER) does not exceed 0.15 with a channel capacity (CC) of 2 Gbps. For validation, the antenna was fabricated based on two elements and tested experimentally. Finally, it was revealed that the measured results agree very well with simulations after comparing the theoretical calculations with the measured data. Recently, microstrip antennas were introduced in many wireless communication networks including 5G systems for their desired properties, including a low profile and inexpensive fabrication costs . NeverthLater, several studies were applied to design an antenna that supports more than one application; for instance, in  an anten2 when printed on an FR4 substrate of 1 mm thickness.This antenna array is designed from two antenna elements printed on the same substrate for MIMO system design. Each antenna element is structured from three main parts: a printed monopole, an interdigital capacitor array, and a meander line. The proposed antenna is fed with CPW to eliminate the ground plane on the same patch side as well as ensure harmonics generation by accumulating the electrical charge on the ground plane . TherefoFor the MIMO configuration, the authors applied the design of two elements that are mounted on the same substrate with the same direction, as shown in It is important to note that the introduction of the meander line has the effect of producing a frequency band that is distinct from the band emitted by the monopole, as will be demonstrated later. To regulate the mobility of the antenna surface current, an LDR switch is used to link the planned meander line to the antenna ground plane. The key benefit of including the interdigital capacitor in the design is that it may be used to balance the monopole antenna structure’s induction effect and match the electromagnetic aperture coupling to the free space impedance. As will be demonstrated later , this woAs shown in In terms of mathematics, the suggested unit cell was examined from various orientation angles at normal and tangential electric field incidences. Yet, in this inquiry, the planned unit cell iteration was raised from the first to the fourth with a single step. This was done to make sure that the performance of the suggested unit cell is improved by the iteration effects. As a result, the suggested unit cell is situated inside a fictitious waveguide to track the S-parameter spectra at the targeted frequency range. With the application of two electrical and two magnetic barriers to the virtual waveguide, the effective medium theory is invoked in this simulation process. A similar procedure is used to simulate the creation of transverse electromagnetic modes as a plane wave .12 and S11 spectra, are shown in Now, after inserting the proposed unit cell with different orientations and different iterations, the calculated S-parameters, in terms of S11 spectra are investigated with respect to varying the separation distance between the monopole and the ground plane (Xg). Therefore, the considered distance Xg was changed from 1 to 5 mm with a step of 1 mm with respect to monitoring S11 spectra as shown in In this section, the proposed monopole element performance in terms S11 spectra with respect to varying the ground plane length (Yg).Now, to investigate the effects of increasing the ground plane length on the antenna frequency resonance, the authors considered Xg = 3 mm, but the ground plane length was changed from 8 to 5 mm with a step of 1 mm. It was observed that with decreasing the ground plane length, there was a significant decay in the antenna second mode frequency resonance. Therefore, it is concluded the ground plane length (Yg) is better to be 5 mm for our applications. Reducing the length to less than 5 mm is not very desired during the fabrication process due to soldering limitations . The cal11 spectra. Therefore, the monopole width (Xm) was changed from 1 to 5 mm. It was found that the observable variation in the term of S11 spectra is specific to bandwidth, matching, and frequency resonance, as depicted in For further analysis, the authors studied the effects of varying the monopole width on the antenna S11 and gain spectra. Therefore, the proposed IDC iteration number was changed from the first to the fourth degree. The effects of that on S11 and gain spectra are shown in C is the capacitance per unit length (l) with respect to the finger width (W), A1 (the interior) and A2 (the two exteriors) are the capacitances per unit length of the fingers, and N is the number of fingers and can be expressed in microns. For infinite substrate thickness (or no ground plane), A1 = 4.409 × 10−6 pF/mm and A2 = 9.92 × 10−6 pF/mm.Since the introduction of the IDC structure to the proposed antenna could cause a significant performance change, the authors applied a study to evaluate the antenna SNow, the antenna gain spectra over the entire frequency band of interest are discussed with respect to the same IDC iteration variation as shown in 11 and gain spectra variation. As shown in The authors introduced a meander line to examine the effects of coupling between the ground plane and the antenna parts. Such coupling is due to the effects of the electrical field fringing from the antenna edges . The effNow, the antenna gain was found to increase when increasing the turn number, as seen in 11 spectra are insignificantly affected by increasing D. This is a usual response because the fact of changing S11 spectra is relative to varying the antenna elements’ dimensions [12 spectra, the manner of the antenna mutual coupling variation is different; it is increased with decreasing the distance between the antenna elements, as shown in Now, the proposed antenna was designed to be configured as an array with two elements, as shown in mensions . However12 below −20 dB, as seen in r) over the frequency bands of interest. Therefore, the propagated surface current toward the array center is a decayed mode with a significant attention factor [Our philosophy in this research was to reduce the antenna element size within a miniaturized array configuration by adding MTM defects. Such an addition can be implemented to minimize the separation distance ultimately to 6 mm with coupling effects in terms of Sn factor .12 reduction is achieved when four-unit cells are introduced to the proposed array, as seen in 12 below −20 dB and S11 ≤ −10 dB. It is concluded from these results that the proposed metamaterial array behaves as a stop-band filter to reject most of the frequencies within the frequency band of interest, as discussed later.Now, the proposed antenna array is introduced to a metamaterial unit cell column in the back panel to eliminate the mutual coupling between the antenna edges. In our design, we introduced the proposed unit cell parametrically, from one to four with the step of the one-unit cell, to minimize the mutual coupling altimetry. Therefore, it is observed from the evaluated S-parameters results, in We next evaluated the antenna TRAC using the effective antenna gain for the optimal antenna performance with different signal phase excitations at Port 2 of 0°, 30°, 60°, and 90°. The obtained results are depicted in The antenna radiation efficiency was evaluated for both cases of with and without MTM introduction. The calculated results are presented in The proposed antenna array was designed for reconfigurable MIMO systems based on sub-6 GHz to suit the applications of 5G networks. Therefore, it is very obvious that such systems require antenna terminals of configurable performance . In our 11 and S12 spectra in 12 spectra are usually a measure of coupling between the adjacent antennas that has no response to LDR-switching scenarios. This observation was discussed earlier in [Our target was to control the surface current on the antenna element by controlling the real impedance at a certain point, in which most of the charge accumulation could accrue . It is wrlier in .2. The proposed antenna S-parameters were measured using an HP vector network analyzer.Now, to validate the proposed antenna array performance experimentally, the proposed array was fabricated using a chemical wet etching process. As seen in The measured antenna radiation patterns were considered at 3.5, 4, 4.5, 5, and 5.5 GHz inside an RF chamber. This process was invocated after calibrating all processes in the channel using the through calibration technique, and open, short, and 50 Ω load. The obtained result from the experimental measurements was evaluated for only two switching scenarios; when all LDR terminals are on and off only. The obtained results are shown in Below, the antenna radiation measurements are presented in The antenna performance in terms of correlation and diversity envelopes was evaluated experimentally to be compared with the simulated results in To realize the effects of using the proposed MTM on the proposed antenna performance, a comparison study is summarized at the end of the discussions to focus on the role of the proposed MTM unit cell. In Now, to present a complete picture of the proposed antenna array performance, the authors evaluated the channel capacity (CC) and the bit error rate (BER) under the assumption of constructing an antenna array of 64 × 64 elements, theoretically only; for such an assumption, we tried to perform an analytical validation of such antenna feasibility for massive MIMO systems. The calculated CC and BER are based on measured results from the antenna elements in terms of gain, bandwidth, and mutual coupling. The channel is affected by white Gaussian noise and the transmitted power was changed from −20 to 20 dBm. In such circumstances, the maximum bit error rate was found to be about 0.15, and the channel capacity was found to reach 2 Gbps. The obtained results are presented in erfc is the complementary error function, bE is the bit energy, oN is noise power, and BW is the available bandwidth.The evaluated BER and CC were calculated using the following mathematical expressions :BER=erfcIn those calculations, a digital modulation schema based on quadrature-amplitude modulation (QAM) with an effective coverage was applied to indicate the effects of that on BER. The considered BER in this case is defined as the number of acceptable errors at the prepared tolerates. In such a case, typically, it is a number between 0.1 and 0.000001. This ratio is very much affected by the signal-to-noise ratio (SNR), which is measured in dB. It was found from the results in Finally, the proposed antenna array performance was compared with the published results in the literature in terms of antenna bandwidth, gain, size, reconfigurability, and substrate type. It was observed that the proposed antenna array shows a maximum-size reduction with excellent configuration technique and performance in comparison with the previous one listed in In this paper, the authors designed a miniaturized antenna array for MIMO applications. The proposed antenna parameters were optimized to fit the applications of sub-6 5G networks in terms of mutual coupling reduction, bandwidth enhancements, and gain increase. Therefore, the authors applied in the proposed design several techniques to realize a highly miniaturized antenna array with excellent reconfiguration mechanisms. For this, a monopole fundamental antenna element is conjugated with a meander line and interdigital capacitor to increase the antenna radiation efficiency with low surface wave retardation. In such a manner, fitting the proposed antenna element in a single array could be an excellent addition to MIMO systems by minimizing the separation distance between them using a metamaterial structure. The proposed metamaterial was found to realize a significant mutual reduction of almost −20 dB over the frequency band from 3 up to 5.5 GHz with a separation distance of 0.08 λ. This antenna array was tested with different configuration scenarios by adding four LDR switches to each antenna element through the meander line and the ground plane. We realized that such a reconfiguration process takes advantage of low complexity without including wiring or biasing systems. It was found that when exposed to a massive MIMO environment in the proposed antenna array, acceptable BER and CC can be achieved after making the antenna size theoretically 64×64 elements. It is concluded from this study that the proposed antenna array is a very suitable candidate for 5G massive MIMO systems at the sub-6 GHz frequency band. Finally, for validation, an experimental study was applied to the proposed array to test the antenna performance in terms of S-parameters and radiation patterns.