Mutual coupling suppression between two closely placed microstrip patches using EM-bandgap metamaterial fractal loading

An approach is proposed to reduce mutual coupling between two closely spaced radiating elements. This is achieved by inserting a fractal isolator between the radiating elements. The fractal isolator is an electromagnetic bandgap structure based on metamaterial. With this technique, the gap between radiators is reduced to ∼0.65λ for the reduction in the mutual coupling of up to 37, 21, 20, and 31 dB in the X-, Ku-, K-, and Ka-bands, respectively. With the proposed technique, the two-element antenna is shown to operate over a wide frequency range, i.e., 8.7–11.7, 11.9–14.6, 15.6–17.1, 22–26, and 29–34.2 GHz. Maximum gain improvement is 71% with no deterioration in the radiation patterns. The antenna’s characteristics were validated through measurement. The proposed technique can be applied retrospectively and is applicable in closely placed patch antennas in arrays found in multiple-input multiple-output and radar systems

Mutual Coupling Suppression Between Two Closely Placed Microstrip Patches Using EM-Bandgap Metamaterial Fractal Loading

An approach is proposed to reduce mutual coupling between two closely spaced radiating elements. This is achieved by inserting a fractal isolator between the radiating elements. The fractal isolator is an electromagnetic bandgap structure based on metamaterial. With this technique, the gap between radiators is reduced to ∼0.65λ for the reduction in the mutual coupling of up to 37, 21, 20, and 31 dB in the X -, Ku -, K -, and Ka -bands, respectively. With the proposed technique, the two-element antenna is shown to operate over a wide frequency range, i.e., 8.7–11.7, 11.9–14.6, 15.6–17.1, 22–26, and 29–34.2 GHz. Maximum gain improvement is 71% with no deterioration in the radiation patterns. The antenna’s characteristics were validated through measurement. The proposed technique can be applied retrospectively and is applicable in closely placed patch antennas in arrays found in multiple-input multiple-output and radar systems

Study on isolation improvement between closely packed patch antenna arrays based on fractal metamaterial electromagnetic bandgap structures

A decoupling metamaterial (MTM) configuration based on fractal electromagnetic bandgap (EMBG) structure is shown to significantly enhance isolation between transmitting and receiving antenna elements in a closely packed patch antenna array. The MTM-EMBG structure is cross-shaped assembly with fractal slots etched in each arm of the cross. The fractals are composed of four interconnected ‘Y-shaped’ slots that are separated with an inverted ‘T-shaped’ slot. MTM-EMBG structure is placed between the individual patch antennas in a 2×2 antenna array. Measured results show the average inter-element isolation improvement in the complete band of interest is 17 dB, 37 dB and 17 dB between radiation elements #1 & #2, #1 & #3, and #1 & #4, respectively. With the proposed method there is no need for metallic via-holes. The proposed array covers the frequency range of 8- 9.25 GHz for X-band applications, which corresponds to a fractional bandwidth of 14.5%. With the proposed method the edge-to-edge gap between the antenna can be reduced to 0.5λ0 with no degradation in the antenna’s radiation patterns. The gain of the antenna array varies between 4 dBi and 7 dBi. The proposed method is applicable for implementation of closely packed patch antenna arrays, e.g. multiple-input-multiple-output (MIMO) systems, and synthetic aperture radars (SAR)

A Comprehensive Survey on 'Various Decoupling Mechanisms with Focus on Metamaterial and Metasurface Principles Applicable to SAR and MIMO Antenna Systems'

Nowadays synthetic aperture radar (SAR) and multiple-input-multiple-output (MIMO) antenna systems with the capability to radiate waves in more than one pattern and polarization are playing a key role in modern telecommunication and radar systems. This is possible with the use of antenna arrays as they offer advantages of high gain and beamforming capability, which can be utilized for controlling radiation pattern for electromagnetic (EM) interference immunity in wireless systems. However, with the growing demand for compact array antennas, the physical footprint of the arrays needs to be smaller and the consequent of this is severe degradation in the performance of the array resulting from strong mutual-coupling and crosstalk effects between adjacent radiating elements. This review presents a detailed systematic and theoretical study of various mutual-coupling suppression (decoupling) techniques with a strong focus on metamaterial (MTM) and metasurface (MTS) approaches. While the performance of systems employing antenna arrays can be enhanced by calibrating out the interferences digitally, however it is more efficient to apply decoupling techniques at the antenna itself. Previously various simple and cost-effective approaches have been demonstrated to effectively suppress unwanted mutual-coupling in arrays. Such techniques include the use of defected ground structure (DGS), parasitic or slot element, dielectric resonator antenna (DRA), complementary split-ring resonators (CSRR), decoupling networks, P.I.N or varactor diodes, electromagnetic bandgap (EBG) structures, etc. In this review, it is shown that the mutual-coupling reduction methods inspired By MTM and MTS concepts can provide a higher level of isolation between neighbouring radiating elements using easily realizable and cost-effective decoupling configurations that have negligible consequence on the arrays characteristics such as bandwidth, gain and radiation efficiency, and physical footprint

A Comprehensive Survey on “Various Decoupling Mechanisms With Focus on Metamaterial and Metasurface Principles Applicable to SAR and MIMO Antenna Systems”

Nowadays synthetic aperture radar (SAR) and multiple-input-multiple-output (MIMO) antenna systems with the capability to radiate waves in more than one pattern and polarization are playing a key role in modern telecommunication and radar systems. This is possible with the use of antenna arrays as they offer advantages of high gain and beamforming capability, which can be utilized for controlling radiation pattern for electromagnetic (EM) interference immunity in wireless systems. However, with the growing demand for compact array antennas, the physical footprint of the arrays needs to be smaller and the consequent of this is severe degradation in the performance of the array resulting from strong mutual-coupling and crosstalk effects between adjacent radiating elements. This review presents a detailed systematic and theoretical study of various mutual-coupling suppression (decoupling) techniques with a strong focus on metamaterial (MTM) and metasurface (MTS) approaches. While the performance of systems employing antenna arrays can be enhanced by calibrating out the interferences digitally, however it is more efficient to apply decoupling techniques at the antenna itself. Previously various simple and cost-effective approaches have been demonstrated to effectively suppress unwanted mutual-coupling in arrays. Such techniques include the use of defected ground structure (DGS), parasitic or slot element, dielectric resonator antenna (DRA), complementary split-ring resonators (CSRR), decoupling networks, P.I.N or varactor diodes, electromagnetic bandgap (EBG) structures, etc. In this review, it is shown that the mutual-coupling reduction methods inspired By MTM and MTS concepts can provide a higher level of isolation between neighbouring radiating elements using easily realizable and cost-effective decoupling configurations that have negligible consequence on the array’s characteristics such as bandwidth, gain and radiation efficiency, and physical footprint

Isolation Enhancement of Densely Packed Array Antennas with Periodic MTM-Photonic Bandgap for SAR and MIMO Systems

A metamaterial photonic bandgap (MTM-PBG) periodic structure is used as a decoupling frame to improve the isolation between transmit–receive (T/R) sections of densely packed array antenna in synthetic aperture radar (SAR) and multiple-input multiple-output (MIMO) systems. With this technique the MTM-PBG structure is shown to effectively suppress surface wave propagations between the T/R array antennas by an average of 12dB. MTM-PBG layer comprises a periodic arrangement of dielectric circles etched in the cross-shaped microstrip frame that is inserted between the radiating elements. Unlike other recently reported methods, the advantages of the proposed technique are:(i) simplicity; (ii) cost effectiveness as there is no need for short-circuited via-holes or 3D metal walls; and (iii) can be retrofitted in existing array antennas. The proposed T/R array antennas were designed to operate over an arbitrary frequency range (9.25-11GHz) with a fractional bandwidth (FBW) of 17.28%. With this technique (i) the side-lobes are reduced; (ii) there is minimal effect on the gain performance; and (iii) the minimum edge-to-edge gap between adjacent radiating elements can be reduced to 0.15at 9.25GHz

A Review on Different Techniques of Mutual Coupling Reduction Between Elements of Any MIMO Antenna. Part 2: Metamaterials and Many More

This two‐part article presents a review of different techniques of mutual coupling (MC) reduction. MC reduction is a primary concern while designing a compact multiple‐input‐multiple‐output (MIMO) antenna where the separation between the antennas is less than λ0/2, that is, half of the free‐space wavelength. The negative permittivity and permeability of artificially created materials/structures (Metamaterials) significantly help reduce MC among narrow‐band compact MIMO antenna design elements. In this part two of the review paper, we will discuss techniques: Metamaterials; Split‐Ring‐Resonator; Complementary‐Split‐Ring‐Resonator; Frequency Selective Surface, Metasurface, Electromagnetic Band Gap structure, Decoupling and Matching network, Neutralization line, Cloaking Structures, Shorting vias and pins and few more

High-Isolation Leaky-Wave Array Antenna Based on CRLH-Metamaterial Implemented on SIW with ±30o Frequency Beam-Scanning Capability at Millimeter-Waves

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

Interaction suppression technique for high-density antenna arrays for mm-wave 5G MIMO systems

This paper presents the feasibility study of applying a combination of suppression techniques to improve isolation between the radiation elements in high-density antenna arrays and thereby improve the arrays impedance bandwidth and radiation performance. High isolation between adjacent radiation elements was achieved by embedding a crisscrossed decoupling structure comprising slotted microstrip-lines and locating in the ground-plane under each slot a dielectric ring. The proposed periodic array behaves as artificial magnetic conductor (AMC) surfaces as incident waves in the substrate are fully reflected with a near zero degrees reflection phase. The proposed technique suppresses surface-wave propagation. Proof of concept was verified by applying the technique to a 2×4 linear array of triangular radiation patches designed to operate between 30-35 GHz. The array was implemented on a standard the Rogers RT 5880 substrate. Dimensions of the array are 40×20×0.8 mm3. Measurement confirm improvement is the array’s impedance bandwidth, fractional bandwidth, average isolation, radiation gain, and efficiency by 2 GHz, 6.15%, >10 dB, 6.6 dBi, and 29%. The array operates across 30–35GHz with average isolation between its radiation elements better than 23 dB, average gain and efficiency of 12 dBi and 85%, respectively. The technique can be applied to mm-Wave 5G MIMO systems

Design of a Novel Efficient High-Gain Ultra-Wide-Band Slotted H-Shaped Printed 2×1 Array Antenna for Millimeter-Wave Applications with Improvement of Bandwidth and Gain via the Feed Line and Elliptical Edges

This paper describes design procedure of a high-performance miniaturized antenna with an array configuration, which contributes to enhancing the communication system’s performance. The basic antenna features a compact size (6 x 6) mm2, and its single element is an H-shaped slotted patch printed on the top side of a Rogers RT5880 substrate, with a relative permittivity and thickness of 2.2 and 0.3 mm, respectively. The edge-to-edge distance of the 2 × 1 array antenna is 9 x 14 mm2, and the isolation between its radiation elements is 4.5 mm. To increase the capabilities of the antenna in terms of gain and bandwidth, we proceeded to use the 2 × 1 array configuration and then optimized the model via either the width of the feed line or the elliptical edges of the patch. The miniaturized array antenna achieved a peak gain of 12.56 dB, a directivity of 13.11 dBi, and a return loss of -47.52 dB at a resonance frequency of 91.5 GHz, with a radiation efficiency of more than 91% over an operating bandwidth of 15.83 GHz, ranging from 79.7 GHz to 95.6 GHz. The design and simulation results of the proposed antenna were obtained using the CST Studio software