Free-space Wavelength Research Articles

Low-profile metasurface lens antenna with flat-top radiation pattern

This paper proposes a low-profile metasurface (MS) lens antenna with flat-top radiation pattern. Specifically, a low-profile slot array fed by the pillbox system serves as the feeding source while an MS lens placed close to the slot array can further shape the beam to flat-top radiation pattern. Compared with the conventional MS lens antennas with a single feeding source, the overall profile is greatly reduced and the fabrication stability is improved. Theoretical analyses, simulations, and measurements are carried out in this study. The proposed MS lens antenna operates at a central frequency of 28.5 GHz, aiming at supporting 5G millimeter-wave (mmW) communications. The measured results agree well with the analyzed and simulated ones. The proposed MS antenna realizes the flat-top pattern of over ± 20° with the measured peak gain of 10.5 dBi. The overall size is 78 mm × 63 mm × 4.4 mm, corresponding to 7.4λ0 × 6λ0 × 0.42λ0 at 28.5 GHz (λ0 is the free-space wavelength).

Compact Sub 6 GHz Dual Band Twelve-Element MIMO Antenna for 5G Metal-Rimmed Smartphone Applications.

In this paper, a twelve-antenna system is designed for 5G smartphones with metal frames. The system is compact and operates on dual bands within the sub-6 GHz frequency range using multiple-input multiple-output (MIMO) technology. Two sets of six-antenna units are included in the system, arranged in a diagonal mirror-image configuration, and positioned at the center of the circuit board's longer edges. The profile height of each of the six-antenna units is only 3 mm, and the overall array dimensions are 105 × 3 × 3.1 mm3. A single antenna unit is 15 × 3 × 3.1 mm3 (0.173 λ × 0.035 λ × 0.036 λ, where λ equals the free-space wavelength of 3450 MHz). The arrangement of the antennas in the six-antenna units is parallel, with a 3 mm separation between adjacent antennas. The antenna structure comprises of an inverted L-shaped feed branch and two inverted L-shaped short-circuit branches integrated into part of the metal frame. The proposed array can form multiple resonance paths, achieving dual-band operation at 3300-3600 MHz and 4800-5000 MHz. The measured isolation of this twelve-antenna system within the operating frequency band is over 10 dB, and the measured antenna efficiency is greater than 36%. Therefore, the system is suitable for use in smartphones with high screen-to-body ratios and metal frames.

A wideband omnidirectional dipole antenna with parasitic loop based on multi-resonant modes

ABSTRACT A wideband omnidirectional dipole antenna with parasitic loop based on multi-resonant modes is proposed for WLAN, 5 G Sub-6 GHz, and RFID applications. The antenna is composed of a regular dipole with co-planar strips and a parasitic loop with four U-shaped branches. A regular dipole with co-planar strips is used to generate two resonant modes, and the parasitic loop around it generates another two resonant modes. By combining these four resonant modes, a wideband characteristic is achieved. In order to reduce the cross-polarization, four U-shaped branches are introduced, and then the cross-polarization levels are decreased from −2 dB to −13 dB. A prototype with a compact size of 0.6λ0 ×0.56λ0 ×0.012λ0 (λ0 is the wavelength in free space at center frequency) is fabricated and tested. Measurement shows that effective bandwidth is 1.8–5.6 GHz (102.7%), the measured gain variation is only 1.3 dBi, and omnidirectional radiation patterns are achieved over the operating band.

A Low-Profile Broadband Dual-Polarized Omnidirectional Antenna for LTE Applications

In this letter, a broadband dual-polarized antenna with a very low profile and omnidirectional gain patterns is designed for 1.7-2.7 GHz Long Term Evolution (LTE) mobile communications. The designed antenna is constituted by a miniaturized tapered monopole for vertical polarization (VP) and four planar dipoles arranged in a ring for horizontal polarization (HP). The HP antenna is used as the metal ground of the VP antenna, which can avoid the feeding intersection and solve the problem of impedance matching degradation when distance between the HP antenna and the metal ground of the VP antenna is close. By sharing the partial structure, the designed antenna achieves a compact size of 110 mm × 110 mm × 13 mm and an extremely low height of 0.07 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> is the free-space wavelength at the minimum operating frequency). The design achieves an overlapping bandwidth of 45% (1.7-2.7 GHz) with an isolation higher than 20 dB. High efficiency, low cross polarization and good omnidirectivity in the horizontal plane are obtained. The designed antenna is fabricated and measured, and it performs a great consistency between the simulation and measurement.

Low-Profile Planar Ultrawideband Modular Antenna Array Loaded With Parasitic Metal Strips

A low-profile dual-polarized planar ultrawideband modular antenna (PUMA) array is proposed in this paper. The overall profile is as small as 11.4 mm (0.228λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>high</i></sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>high</i></sub> is the free-space wavelength at the highest operating frequency) based on element sizes 25 × 25 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> (0.5 × 0.5λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>high</i></sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) and a large operating frequency bandwidth achieved by loading lossless parasitic metal strips between the dipole patch and the ground plane. The loop-mode resonance that causes deterioration of the port isolation around the lowest operating frequency is comprehensively analyzed and suppression methods are proposed. To further reduce the overall profile, a metasurface-based wide-angle impedance matching (MS-WAIM) layer is introduced. The surface waves guided by the MS-WAIM layer during wide-angle scanning in H-plane are suppressed by cutting properly-sized square holes at critical positions. The calculated results show that the proposed infinite array can scan up to ±60° in E/H-planes with active VSWRs below 2.9 within 2–6 GHz and orthogonal port isolations beyond 20 dB. A 12 × 11 array prototype is fabricated and reasonable agreement is achieved between the calculated and measured results.

Low-Profile Compact Tri-Band Multimode Reconfigurable Antenna Using Characteristic Mode Analysis

A low-profile compact tri-band (2.45/3.5/5.8 GHz) reconfigurable antenna with versatile radiation modes is proposed for portable wireless communication in this paper. The characteristic mode analysis method is used to explain the antenna’s operating principles and reduces the dimension. The antenna primarily comprises a patch radiator with T-shaped cuts, meander-slot defected ground, and shorting pins, resulting in three frequency bands with different radiation patterns. The antenna features a compact volume of 0.24λ0 × 0.24λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.026λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength of 2.45 GHz) and exhibits omnidirectional radiations at 2.45 and 5.8 GHz and unidirectional radiations at 3.5 GHz. In addition, the operating bands can be tuned by applying different DC biases to the varactors. The antenna is fabricated, and the measured results agree reasonably well with the simulations. The miniaturized tri-band antenna can be potentially used in portable wireless services and intelligent transport devices.

Subwavelength-Cavity High-Gain Circularly Polarized Antenna with Planar Metamaterials

We present a specific subwavelength-cavity high-gain circularly polarized ultra-thin antenna made of planar metamaterials. The antenna is designed to operate at 2.80 GHz with a fixed thickness of approximately 1/6 of the operating wavelength in free space. The asymmetric unit cells of the metamaterial antenna exhibit two characteristics, namely, negative permeability and polarization selection. A linear-polarization micro-strip patch, which can realize circular polarization without a complicated feeding network, is embedded in the cavity as a feed. The circular polarization mode of the antenna can be changed by simply rotating the planar metamaterial horizontally. Simulations and experiments conducted on this antenna yielded results that are in good agreement with each other. This new subwavelength planar antenna can have potentially important applications in communication, early warning systems, and radio observation.

MmWave self-beam-tilting antenna array with low complexity and wide coverage

This paper proposes an effective planar mmWave switched beamforming antenna array with low complexity and wide beam coverage. The proposed structure is configured using multiple linearly polarized self-beam-tilting-antenna (SBTA) elements, eliminating the requirement of a phase-adjustable block for beamforming. Each SBTA element can generate different main beam directions by itself without using complicated feed networks. Moreover, unlike typical Butler matrix-based beamforming arrays, the proposed SBTA array does not require passive hybrid couplers to adjust the phases for beamforming operations. Accordingly, the proposed feed network-less antenna avoids circuit complexity, feed network insertion losses, or increases in size and fabrication costs, rendering it suitable for mmWave compact antenna applications. To verify the proposed concept and beamforming performance, a 1 × 4 SBTA array was fabricated at 28 GHz using a conventional printed circuit board (PCB) process. The size of the fabricated antenna (excluding test connectors) was 1.12 λ0 × 1.68 λ0 × 0.08 λ0 (λ0 for free-space wavelength), and the measured 10-dB impedance bandwidth was approximately 5.9 %. Furthermore, the measured main beam switching directions were found at −34°, −52°, +51°, and +38° with measured gains of 6.7, 6.1, 5.9, and 6.6 dBi, respectively, at 28 GHz.

A Differential Microwave Sensor Loaded With Magnetic-LC Resonators for Simultaneous Thickness and Permittivity Measurement of Material Under Test by Odd- and Even-Mode

A differential microwave sensor for simultaneously retrieving thickness and dielectric constant of material under test (MUT) based on magnetic-LC (MLC) resonator is proposed in this manuscript. The procedure of designing proposed microwave sensor is illustrated as follows: 1) Designing a splitter/combiner; 2) Separately etching an MLC resonator under every microstrip branch of splitter/combiner; 3) The symmetry axis of electric wall of each resonator is moved by an offset distance away from the center of every microstrip branch, so the odd- and even-mode will be produced. One resonator is regarded as reference, the other is used as test. From numerical simulation, the electric fields of odd- and even-mode are mainly concentrated at the center arm and two sides of the resonator, respectively. The area of resonator is regarded as sensing region. The equivalent circuit model is adopted to illustrate the operating principle of the proposed sensor. The mathematical model of the relative frequency shifts of two resonant modes with respect to thickness and permittivity of loaded MUT can be established by simulated data. In measurement, the unloaded odd/even-mode resonant frequency and quality factor are 2.5875/5.625 GHz and 251/77.67, respectively. The maximum errors for retrieving permittivity and thickness are about 4.02% and 8.4%, respectively. Besides, the sensitivities for odd- and even-mode are separately calculated as 2.21% and 1.38%, if permittivity and thickness of MUT are set as 6 and 0.1mm, respectively. If the lowest sensitivity of even-mode is set as 0.31%, then the minimum size of MUT is about 3.4 mm×10 mm×0.1 mm. With comparison to traditional microstrip sensors, the proposed sensor can simultaneously retrieve thickness and permittivity of MUT by odd- and even-mode, and it can reduce interferences of external environment by virtue of differential structure. The proposed microwave sensor has a compact size of about 0.43λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.436λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength in free space at 2.5875 GHz), and it is a good candidate in the field of characterizing solid materials with some superiorities.

Design and analysis of planar four-port UWB-MIMO antenna with band-rejection capability

Abstract This manuscript presents a 50 Ω microstrip-fed quad-element high isolated ultra-wideband (UWB) multiple-input multiple-output (MIMO) antenna with band-notched characteristics. The overall area of the proposed structure is 0.33λo × 0.33λo mm2 (where λo depicts the free space wavelength corresponding to the lower cutoff frequency, i.e. 2.54 GHz), etched on an FR-4 substrate of thickness 0.8 mm. The top layer has four semicircular disc-shaped radiating elements that are identical and orthogonal to obtain better inter-element isolation and compactness. A reverse two-shaped slot is etched onto the radiating patches to attain a band-rejection capability. Moreover, a decoupling structure is also placed at the top layer to suppress the unwanted surface waves. The bottom layer consists of a ground plane, which is further modified with quasi-self complementary and meandered line slots. A rectangular slot is also etched below the feed line to better match the impedance near the lower cutoff frequencies. The simulated reflection coefficients (S11) of the proposed antenna are less than −10 dB over 2.54 to 10.74 GHz frequencies except at 3.37 to 4.15 GHz (WiMAX/C band), and the simulated inter-port isolation (S21) is greater than −15 dB over the entire UWB range of frequencies (3.1 to 10.6 GHz). Also, the measured S-parameter results well agreed with the simulated ones. Furthermore, the simulation study of the 20-element UWB-MIMO antenna is also investigated using the proposed quad-element structure.

Low Profile Dual-Band Polarization Conversion Metasurface with Omnidirectional Polarization.

In this work, a dual-band transmissive polarization conversion metasurface (PCM), with omnidirectional polarization and low profile, is proposed. The periodic unit of the PCM is composed of three metal layers separated by two substrates. The upper patch layer of the metasurface is the patch-receiving antenna, while the bottom layer is the patch-transmitting antenna. Both antennas are arranged in an orthogonal way so that the cross-polarization conversion can be realized. The equivalent circuit analysis, structure design, and experimental demonstration are conducted in detail, the polarization conversion rate (PCR) is greater than 90% within two frequency bands of 4.58-4.69 GHz and 5.33-5.41 GHz, and the PCR at two center operating frequencies of 4.64 GHz and 5.37 GHz is as high as 95%, with a thickness of only 0.062λL, where λL is the free space wavelength at the lowest operating frequency. The PCM can realize a cross-polarization conversion, when the incident linearly polarized wave at an arbitrary polarization azimuth, which indicates that it has the characteristics of omnidirectional polarization.

Investigation of a quad-band microstrip antenna using a DNG-MTM radiation patch

A compact quad-band microstrip antenna based on double-negative metamaterial (DNG-MTM) is proposed in this letter. To realize miniaturization and multi-band characteristics, a novel coplanar tri-band DNG-MTM unit, consisted of an epsilon negative (ENG) MTM and a mu negative (MNG) MTM, is firstly designed and employed as the antenna radiator. The antenna’s electrical dimension is 0.23λ0 × 0.37λ0, where λ0 is the free space wavelength at 3.5 GHz. The peak gain is 5.3, 6.3, 5.8, and 3.4 dBi and the radiation efficiency reaches 96%, 82%, 91% and 86% for 2.84–3.55 (22.2%), 6.6–7.18 (8.4%), 7.44–9.08 (19.9%), and 11.1–14.74 (28.2%) GHz, respectively. These four bands have effectively covered 5G (3.5-GHz), C-band, X-band, and Ku-band for satellite systems. The size of the proposed antenna has been reduced by about 55% in comparison to the traditional method.

Broadband, Low-Profile, Planar Reflectarray Antenna Based on an Achromatic Metasurface

This paper presents a broadband, low-profile, and planar reflectarray antenna based on an achromatic metasurface. The achromatic metasurface has advantageous broadband focusing capabilities compared to conventional reflectarrays. Six types of unit cells offering versatile phase responses are employed to design an achromatic metasurface optimized by a convolutional algorithm. A broadband achromatic reflectarray antenna with a diameter of 270 mm is simulated, fabricated, and tested. The test results agree well with the simulated results. Notably, the 3-dB realized gain of the reflectarray antenna reaches a fractional bandwidth of 58.2% at a range of 8.9 GHz to 16.2 GHz. Furthermore, the reflectarray antenna significantly enhances the feeding antenna’s gain from 7.3 GHz to 17 GHz. The reflecting metasurface also has a low profile of 0.11 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> , where λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</sub> is the wavelength in free space at 7.3 GHz. With excellent broadband performance, high gain, low profile and ease of fabrication, the developed reflectarray antenna serves as a promising device for long-distance integrated communication systems.

A novel compact and broadband printed monopole antenna for circular polarization

In this letter, a compact and broadband printed monopole antenna for circular polarization is proposed. In order to reduce the antenna size and achieve the circular polarization, the ground plane is combined by two elliptical shaped conductors with different size, and the antenna is designed asymmetrically to the microstrip line. The simulated and measured bandwidth of the 10dB-return loss with a 3dB-axial ratio is 57.9% (2.65GHz-4.81GHz) and 52.0% (2.45GHz-4.17GHz). The size of the antenna is 0.178 λc2 (λc is a wavelength in free space at the center frequency).

Metasurface-Covered Planar Endfire Antenna With Vertical Polarization

A trapped wave-based solution to design compact planar vertically-polarized (VP) endfire antennas is proposed in this paper. By placing a four-element series-fed magnetic dipole array with an inter spacing of half wavelength within a dual-layer metasurface and loading shorting pin arrays at two edges of the metasurface, the VP radiation is realized in a wide impedance band. In addition, the antenna profile can be further reduced by half according to the electric field distribution within the metasurface. Finally, a VP endfire antenna with a reflection bandwidth of 4.3 ~ 5.4 GHz, a peak gain of 9.8 dBi and a low total profile of 0.065λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at the center operation frequency) is designed for the validation. The proposed antenna can be used for some wireless communication systems on or near the ground plane, such as the car roof-mounted terminal for vehicle-to-roadside unit/base station communications.

Generation of broadband non-diffraction millimeter-wave airy beams based on high-efficiency tri-layer metasurfaces

Airy beams based on the Airy function, exhibiting a special curved parabolic trajectory, can effectively alleviate diffraction along its propagation and hold potential in many interesting applications. However, to date, the broadband and high-efficiency generation of non-diffraction Airy beams has remained largely unexplored, especially in the millimeter-wave range that is full of great application potential. In this paper, broadband 1-D and 2-D Airy beam generators utilizing high-efficiency tri-layer metasurfaces operating from 55 to 67 GHz are presented. The metasurfaces consist of elaborately tailored meta-atoms that can independently realize complete amplitude modulation from 1% to 98% and binary phase tuning of 0 and π. The Airy beam generators are engineered and verified by simulations and experiments, which demonstrate the broadband quasi-non-diffraction feature and curved trajectory of the Airy beam. Compared to the 1-D Airy beam generator, the measured quasi-non-diffraction propagation property of the 2-D Airy beam can be maintained by greater than 160 free-space wavelengths across the entire bandwidth. Self-reconstruction property of the 2-D Airy beam is also experimentally validated in the presence of metallic and dielectric obstacles. This work may benefit novel applications of Airy beams in millimeter-wave imaging and detection.

Homogenization of Periodic Structures Using the Multimodal Transfer Matrix Method

This work presents a method for obtaining the constitutive parameters of periodic structures from the computation of their dispersion relation and average fields. The method uses the scattering parameters of multiple Bloch modes of a single unit cell. The corresponding multimodal scattering matrix is obtained with a suitable general-purpose electromagnetic software. Further post-processing of this scattering matrix is then carried out, which allows for the computation of the dispersion relation of structures with realistic finite conductivity or made of lossy dielectrics, as well as the calculation of the attenuation constant and the retrieval of the impedance, permittivity, and permeability. The proposed method is applied to homogenize some systems of interest: an artificial electric plasma built with wires, a free-space matched left-handed metamaterial based on two laterally shifted split ring resonators, a high-permittivity artificial dielectric based on densely arranged square metal patches, and a μ-near-zero metamaterial made of metallic cubes embedded in a dielectric. The retrieved material parameters are found to accurately describe the scattering of finite samples of the corresponding homogenized structures. This research is limited to orthorhombic unit cells smaller than half the free-space wavelength to avoid diffracted beams. Besides, since only one propagation direction is considered, only the transverse components of constitutive parameters are retrieved.

A Quad-Band Shared-Aperture Antenna Based on Dual-Mode Composite Quarter-Mode SIW Cavity for 5G and 6G with MIMO Capability

This study introduces a new design for an ultra-compact shared-aperture antenna utilizing a quarter-mode substrate integrated waveguide (QMSIW) cavity. The proposed antenna operates as a 4 × 4 multi-input multi-output (MIMO) system in three 5G/6G millimeter-wave (MMw) bands, while functioning as a single element antenna for a 5.5 GHz wireless fidelity Microwave (Mw) band. The antenna comprises four QMSIW cavity resonators; each QMSIW is loaded with dual slots to produce tri-band MMw operation at 28 GHz, 38 GHz, and 0.13 THz. The four cavities are arranged to reuse the entire aperture by creating a conventional open-loop antenna that operates at a frequency of 5.5 GHz. Simulation, measurement, and co-simulation results show that the proposed antenna has a quad-band operation and exhibits favorable characteristics. The measured scattering parameters validate the simulated ones over the four bands under consideration. The lowest values of the measured total radiation efficiencies are 80%, 73%, 62%, and 72% (co-simulation) within the four covered bands, respectively. The antenna peak gains are 1.8 to 1.85 dBi, 4.0 to 4.5 dBi, 4.3 to 4.5 dBi, and 6.5 to 6.6 dBi within the covered bands. Furthermore, the design satisfies MIMO and diversity conditions (envelope correlation coefficient and branch power ratio) over frequency bands of operation. All excellent results are achieved from an ultra-compact size in terms of footprint area (0.018λ02), where λ0 represents the free space wavelength at 5.5 GHz. The antenna boasts an excellent reuse aperture utilization efficiency (RAU) of 92% and a large ratio frequency of 23, making it an ideal candidate for compact devices. With its superior performance, the proposed design is well-suited for a range ofs wireless communication systems, including mobile devices and the Internet of Things.

Polarization insensitive multiband metasurface absorber for L, C, and X band applications

An ultrathin, multiband, polarization insensitive with wide angle stability metasurface absorber having unitcell dimension is proposed ( is the free space wavelength at 1.6 GHz). The four-fold symmetry of the unitcell makes it insensitive to TE and TM polarizations. This metasurface follows the sub-quarter wavelength thickness including an air gap of 2.5 mm and metal backing. The proposed unitcell of the metamaterial absorber (MMA) is designed by parametric optimization and has absorption peaks in L, C, and X bands. This absorber is suitable for applications like radar cross section reduction, isolation, and stealth technologies. The lumped SMD resistors are used to enhance absorption peaks simultaneously in all bands mentioned above. This metasurface has absorptivity of 95%, 99%, 97% & 94% at 1.6 GHz, 5 GHz, 7.5 GHz and 10.2 GHz respectively. This is a polarization-insensitive absorber showing stable absorption for different incidence angles between and at the above-given frequencies. The absorption effect has been studied by investigating the filter effect from the equivalent circuit modeling using surface current distribution and normalized impedance. The proposed structure has been fabricated and its measurement results agree well with the simulated one.

Mutual coupling reduction between closely spaced patch antennas using complementary electric‐field‐coupled resonators

AbstractThis article presents mutual coupling reduction results between closely placed ‐coupled patch antennas using complementary electric field coupled (CELC) resonators. CELC elements are excited by the guided magnetic field and exhibit magnetic resonance. Two configurations are designed, analyzed, and fabricated, with one of them having edge‐to‐edge distance and the other having ( is the free space wavelength for the center frequency). Maximum isolation enhancement of about dB and an average of about dB are achieved in measurement for both designs, respectively. Radiation pattern results show no significant change in both co/cross‐polarization. Excellent agreement is achieved between the simulation and measurement results. The proposed structure is etched on the top plate of the substrate and does not involve a complicated fabrication process or any ground plane modification. The proposed design can be used for mutual coupling reduction of ‐plane coupled array antennas.