Isolation Enhancement of Closely Packed Dual Circularly Polarized MIMO Antenna Using Hybrid Technique

Abstract

Mutual coupling always seriously degrades the antenna performance in multiple-input multiple-output (MIMO) systems but this issue has been rarely investigated for antennas with circular polarization. In this paper, a planar and compact circularly polarized MIMO patch antenna with the polarization diversity is presented. Three grounded stubs and a mirrored F-shaped defected ground structure are used to achieve simultaneous matching and isolation between the two patches with offset feeding for circular polarization. The antenna elements are closely packed with the edge-to-edge distance of 0.06λ 0 at the desired frequency of 2.5 GHz. The measured results indicate that the proposed antenna achieves the impedance matching (S 11 < −10 dB), high isolation (S 12 < −20 dB), and circular polarization (axial ratio<3 dB) within the frequency band of 2.5-2.55 GHz. The radiation patterns and realized gains are measured, showing good agreement between the simulation and measurement. INDEX TERMS Circular polarization (CP), multiple-input multiple-output (MIMO), axial ratio (AR), defected ground slot (DGS), envelope correlation coefficient (ECC), left-hand circular polarization (LHCP), right-hand circular polarization (RHCP).

Dual Circularly Polarized Planar Four-Port MIMO Antenna with Wide Axial-Ratio Bandwidth

“…In addition, the antennas presented in [ 22 , 24 ] had a larger size and separated ground planes. As compared to the antennas in [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ], the proposed dual-CP four-element MIMO antenna offers broader axial ratio and impedance bandwidths and relatively small size. It contains four resonating elements that offer extra degrees of freedom to increase link reliability and communication capacity.…”

“…Therefore, dual-polarized antennas with MIMO features have been gaining popularity in recent years. In the last five years, various CP MIMO antenna configurations have been presented for wireless local area network (WLAN), C-band, and satellite applications [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 ]. In [ 17 ], a dual-port antenna with two resonating elements was proposed for WLAN applications, where the upper square patch with truncated corners showed CP behaviour, while the bottom interdigital-type radiator showed linearly polarized (LP) behaviour.…”

“…In [ 20 ], a patch antenna with protruded L-shaped and inverted L-shaped strips for producing dual circular polarization was suggested. In [ 21 ], a compact MIMO antenna with polarization diversity was reported, where three grounded stubs and an F-shaped defected ground structure (DGS) were used to obtain improved inter-element isolation. A CP MIMO antenna comprising two electromagnetically coupled circular-shaped monopole radiators was presented [ 22 ], where inter-element coupling was improved by using a rectangular decoupling element.…”

“…However, the CP MIMO antennas reported in [ 17 , 18 ] could generate only right-hand CP (RHCP) waves. The CP MIMO antennas in [ 19 , 21 , 23 , 25 ] offered dual circular polarization but exhibited very small axial ratio and impedance bandwidths. Moreover, in most of the above-reported CP MIMO/diversity antennas, the ground planes of the antenna radiators were not associated to each other and, therefore, these antennas could not be used in practical applications [ 26 ].…”

Evolutionary optimization for pattern synthesis and reduction of mutual coupling of linear antenna arrays

“…These side lobes can be suppressed by controlling the control parameters of the antenna arrays. [4][5][6][7][8][9] Different optimization techniques like particle swarm optimization (PSO), [10][11][12][13][14][15][16][17][18][19] genetic algorithm (GA), 20 block Krylov recycling algorithms, 21 hybrid technique, 22 Chichen swarm optimization, 23 using integral operator, 24 PSO, 25 bat algorithm, 26 differential evolution (DE) 21 are being used in the field of the antenna and electromagnetic as well as other fields of engineering and real-life application.…”