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A 3-D metamaterial structure (3DMMS) is proposed and is used to reduce mutual coupling of a twoelement patch antenna array. The 3DMMS consists of an upper M-shaped patch and two lower U-shaped patches, which are connected by two shorted pins. The proposed 3DMMS has a negative permeability at 2.35-2.45 GHz band, which covers the operation band of the patch antenna array with an edge-to-edge array-element distance of 0.13 lambda 0. Five designed 3DMMS cells are embedded into the substrate between two antenna elements, which has a 0.1mm vertical distance to the patch antennas. The proposed antenna is optimized, fabricated and measured. The results show that about 18 dB mutual coupling reduction is achieved by using the 3DMMS without affecting the operating bandwidth and radiation characteristics.

In this article, the authors present the design of a compact multiband monopole antenna measuring 30 × 10 × 1.6 mm3, which is aimed at optimizing performance across various communication bands, with a particular focus on Wi-Fi and sub-6G bands. These bands include the 2.4 GHz band, the 3.5 GHz band, and the 5–6 GHz band, ensuring versatility in practical applications. Another important point is that this paper demonstrates effective methods for reducing mutual coupling through two meander slits on the common ground, resembling a defected ground structure (DGS) between two antenna elements. This approach achieves mutual coupling suppression from −6.5 dB and −9 dB to −26 dB and −13 dB at 2.46 GHz and 3.47 GHz, respectively. Simulated and measured results are in good agreement, demonstrating significant improvements in isolation and overall multiple-input multiple-output (MIMO) antenna system performance. This research proposes a compact multiband monopole antenna and demonstrates a method to suppress coupling in multiband antennas, making them suitable for internet of things (IoT) sensor devices and Wi-Fi infrastructure systems.

A multi-layered electromagnetic band gap (EBG) structure is proposed and incorporated into a MIMO antenna to reduce unexpected mutual coupling between antenna elements. The proposed multi-layered EBG (ML-EBG) structure is comprised of an improved EBG and three loading patches with a same distance. The proposed ML-EBG structure is designed at 2.55 GHz and it is utilized in a MIMO antenna array with an edge-to-edge distance of 0.13 lambda to reduce the mutual couplings. The simulated and measured results have been put forward to prove that the mutual coupling has been reduced by 30 dB between the antenna elements compared to the MIMO antenna without the ML-EBG structure.

Maintaining the compact form of 5G smartphones while accommodating millimeter-wave (mm-wave) bands is a significant challenge due to the substantial frequency difference. To address this issue, we’ve introduced an super-compact 4-port dual-band multiple-input, multiple-output (MIMO) antenna that utilizes a metamaterial-inspired electromagnetic bandgap (EBG) structure. This design minimizes mutual coupling (MC) and handles a wide frequency range effectively. The 4-port MIMO antenna is constructed on a Rogers TMM4 substrate, with overall dimensions of 17.76 × 17.76 mm². It incorporates four planar patch antennas positioned at the corners, arranged perpendicularly to each other. Each antenna element is designed for dual-band operation at 28/38 GHz, featuring a rectangular patch with four rectangular slots and a full ground plane. The gap between these patches measures 0.5 λo, and an EBG is included to minimize MC among the MIMO antenna elements efficiently and cost-effectively. Both simulation and measurement results show a substantial reduction in mutual coupling between the array elements, ranging from −25 to −90 dB. Consequently, this enhances the envelope correlation coefficient (ECC) and improves the total active reflection coefficient (TARC), mean effective gain (MEG), and diversity gain (DG). An in-depth time-domain analysis is proposed to confirm the radiation efficiency of the proposed MIMO antenna design. Furthermore, specific absorption rate (SAR) analysis affirms the suitability of this MIMO antenna for 5G cellular devices operating within the target frequency band.

This article presents a unique meta-inspired decoupling method to reduce the isolation in a multi-band MIMO antenna. The proposed textile-based antenna is designed to cover the frequency spectra of IEEE 802.11a and b/g/n (2.4–2.484 GHz and 5.15–5.85 GHz) WLAN applications. The isolation improvement in multiple WLAN frequencies are achieved by a modified SRR meta-inspired structure without upsetting the parameters of the MIMO antenna. The maximum isolation improvement of around 10 dB is obtained at 2.4 GHz (S21 < −18 dB), 20 dB at 5.2 GHz (S21 < −38 dB) and 10 dB at 5.8 GHz (S21 < −34 dB). The antenna fulfills the dual wideband frequency spectra from 1.34 to 3.92 GHz (56%) and 4.34–6.34 GHz (37.4%). The proposed prototype is fabricated on a jean’s substrate with the dimension of 100 × 60 × 1 mm 3 while a single element occupies the size of 60 × 60 × 1 mm 3 . The gap between two antenna element is 0.1 λ 0 . The measured peak gain in two bands are found around 3 dBi and 5 dBi at 2.4 GHz and 5.8 GHz respectively. The ECC and DG are found around < 0.04 and > 9 respectively over the desired bands. The measured results show a good agreement with the simulated one.

A 4-port multiple-input multiple-output (MIMO) antenna exhibiting low mutual coupling and UWB performance is developed. The octagonal-shaped four-antenna elements are connected with a 50 Ω microstrip feed line that is arranged rotationally to achieve the orthogonal polarization for improving the MIMO system performance. The antenna has a wideband impedance bandwidth of 7.5 GHz with S11 < −10 dB from (103.44%) 3.5–11 GHz and inter-element isolation higher than 20 dB. Antenna validation is carried out by verifying the simulated and measured results after fabricating the antenna. The results in the form of omnidirectional radiation patterns, peak gain (≥4 dBi), and Envelope Correlation Coefficient (ECC) (≤0.01) are extracted to validate the suggested antenna performance. As well, time-domain analysis was investigated to demonstrate the operation of the suggested antenna in wideband applications. Finally, the simulated and experimental outcomes have almost similar tendencies making the antenna suitable for its use in UWB MIMO applications.

In this paper a novel ladder resonator is introduced to reduce mutual coupling effect in the patch antenna array structure. Applied patch antennas are operating at 2.45 GHz frequency, which specially used for MIMO (multiple input multiple output) systems. The edge-to-edge distance between two microstrip patch antennas is 0.05 λ. The proposed ladder resonator impressively blocks the surface current between two patch antennas at the operating frequency, which results in mutual effect reduction. The designed configuration has been analyzed, simulated and measured. Scattering parameters with and without of proposed resonator has been investigated. The result shows that, the proposed configuration increases isolation between two microstrip patch antennas about 44 dB.

A new planar multiple-input–multiple-output (MIMO) antenna for ultra wideband (UWB) applications is presented. The proposed antenna operates over the frequency band from 3.1 to 10.6 GHz and it consists of two identical circular monopoles on an FR4 substrate. The wide isolation is achieved through a novel planar decoupling structure that is being inserted between the dual antennas. Moreover, a center slot is etched on the common ground to further increase isolation. The effectiveness of the decoupling structure is analyzed, and performance study has been performed to investigate the mutual coupling reduction. A good isolation of more than 31 dB has been achieved through the entire UWB band (more than 12 dB improvement over the reference antenna). The proposed UWB antenna with and without the wideband decoupling structure has been investigated and verified both numerically and experimentally. The measurement results of the proposed UWB–MIMO antenna are in good agreement with the simulation results. The proposed UWB antenna has been compared with previous works regarding antenna size, geometric complexity, bandwidth, and isolation level. The proposed antenna has some outstanding characteristics such as a geometric simplicity, compact size, broad bandwidth, and low correlation which give the antenna an excellent diversity performance and a good candidate for UWB applications.

The paper presents a feasibility study on the design of a new metamaterial leaky-wave antenna (MTM-LWA) used in the construction of a 1 × 2 array which is implemented using substrate-integrated waveguide (SIW) technology for millimetre-wave beamforming applications. The proposed 1 × 2 array antenna consists of two LWAs with metamaterial unit-cells etched on the top surface of the SIW. The metamaterial unit-cell, which is an E-shaped transverse slot, causes leakage loss and interrupts current flow over SIW to enhance the array’s performance. The dimensions of the LWA are 40 × 10 × 0.75 mm3. Mutual-coupling between the array elements is suppressed by incorporating a metamaterial shield (MTM-shield) between the two antennas in the array. The LWA operates over a frequency range of 55–65 GHz, which is corresponding to 16.66% fractional bandwidth. The array is shown to exhibit beam-scanning of ±30° over its operating frequency range. Radiation gain in the backward (−30°), broadside (0°), and forward (+30°) directions are 8.5 dBi, 10.1 dBi, and 9.5 dBi, respectively. The decoupling slab is shown to have minimal effect on the array’s performance in terms of impedance bandwidth and radiation specifications. The MTM-shield is shown to suppress the mutual coupling by ~25 dB and to improve the radiation gain and efficiency by ~1 dBi and ~13% on average, respectively.

This paper presents a new approach to suppress interference between neighbouring radiating elements resulting from surface wave currents. The proposed technique will enable the realization of low-profile implementation of highly dense antenna configuration necessary in SAR and MIMO communication systems. Unlike other conventional techniques of mutual coupling suppression where a decoupling slab is located between the radiating antennas the proposed technique is simpler and only requires embedding linear slots near the periphery of the patch. Attributes of this technique are (i) significant improvement in the maximum isolation between the adjacent antennas by 26.7 dB in X-band and >15 dB in Ku and K-bands; (ii) reduction in edge-to-edge gap between antennas to 10 mm (0.37 λ); and (iii) improvement in gain by >40% over certain angular directions, which varies between 4.5 dBi and 8.2 dBi. The proposed technique is simple to implement at low cost.