Isolation Improvement of MIMO Antenna Using Novel EBG and Hair-Pin Shaped DGS at 5G Millimeter Wave Band

Abstract

This paper proposes a hybrid decoupling method based on a novel electromagnetic bandgap (EBG) structure and hair-pin shaped defected ground structure (DGS) to obtain high isolation between 2element multiple input multiple output (MIMO) antenna at 5G millimeter wave band over 27.5−28.35 GHz. The proposed EBG designed on stacked dielectric substrates, achieves a wide frequency band-gap between 26.2−32.03 GHz (20 %). A 2  3 array of the EBG is arranged between two electromagnetically coupled radiating patches in order to suppress the surface wave coupling. Substrate integrated waveguide (SIW) feeding network and cavity are strategically incorporated in the antenna design for improving the radiation performance and minimizing the losses from the feed. EBG shows an average isolation improvement of 13.9 dB within 5G band as compared to unloaded MIMO antenna. The additional reduction in coupling is achieved by placing hair-pin DGS (HP-DGS) on the ground plane, resulting into maximum isolation improvement of 47.7 dB at 27.94 GHz. The prototype of the MIMO was fabricated and experimentally verified. Measured peak isolation between the antennas is obtained as 71.9 dB, having a gain of 9 dBi and front to back ratio (FTBR) of 19.8 dB. A good diversity diversity performance is also noticed for the designed MIMO with envelope correlation coefficient (ECC) of 0.00015, diversity gain (DG) of 9.99 and channel capacity loss (CCL) of 0.025 bits/Hz/sec. Later, SIW corporate feed network is designed for 4-element linear array loaded with EBG and HP-DGS to achieve higher gain and narrow beamwidth. The array was fabricated and the measured results are found in good accordance with the simulation results. The peak gain, beamwidth, and FTBR of the array are 13.3 dBi, 16.2, and 19.97 dB respectively.INDEX TERMS Antenna array, defected ground structure (DGS), electromagnetic bandgap (EBG), mutual coupling reduction, multiple input multiple output (MIMO)

Design Challenges and Possible Solutions for 5G SIW MIMO and Phased Array Antennas: A Review

“…Interestingly, SIW enabled combining various active and passive RF components on a single substrate [26,27]. To date, many efforts have been made to develop SIW MIMO [60][61][62][63][64][65][66][67] and phased array antennas [58,59,[85][86][87][88][89][90]. This paper reviews these categories of antennas and presents their various design possibilities, challenges, and existing solutions, and further indicates the expected MIMO, massive-MIMO, and phased array antenna solutions in SIW technology.…”

“…The mmWave frequency band has the potential to fulfill the very high bandwidth requirements of several Gbps of modern wireless communication. This sub-section reviews SIW MIMO and phased array antennas operating in the mmWave band [53][54][55][56][57][58][59][60][61][62][63][64][65][66][67], and various critical observations of these antennas are summarized in Table III. (a-b).…”

“…Again, a simple SIW cavity-backed MIMO antenna [66] with high isolation and radiation efficiency was reported. The single antenna consists of a SIW cavity-loaded proximity feed patch with a T-shaped stub as shown in Table III.b [66]. The stub cancels out the feed capacitance with its induced inductance.…”

“…20(B) shows that the hair-pin DGS significantly suppressed ground coupling fields. The antenna also utilized two substrates [66] with variable dielectric values to attenuate surface waves to achieve very high isolation over a broader spectrum. In order to reduce radiation leakage losses and port isolations, a SIW transmission line is adopted for signal feeding.…”

“…Therefore, keeping the coupling within limits is challenging but an essential requirement to be fulfilled by antenna designers. Due to limited antenna fabrication space on hand-held/portable devices, bulky and complex decoupling structures are not feasible [29][30]32,66,67]. Recently [46,47], SIW MIMO antennas operating in the sub-6 GHz band were reported where the authors combined the selfdecoupling technique with multiple diversities and avoided the complex decoupling networks.…”