SIW Based Two Element Semi-Circular MIMO Antenna

A High-Order EMSIW MIMO Antenna for Space-Constrained 5G Smartphone

“…Therefore, most of the MIMO antennas are developed using microstrip technology, and very few works are reported in the literature using SIW technology [6]. Moreover, with the advent of hybrid boundary techniques [7,8], miniaturized SIW cavities have been developed [9][10][11][12][13][14][15][16][17][18] and used for compact SIW antennas. They include half-mode SIW (HMSIW), quarter-mode SIW (QMSIW), and eighth-mode SIW (EMSIW) [12,13], which are used to develop compact MIMO antennas.…”

“…They include half-mode SIW (HMSIW), quarter-mode SIW (QMSIW), and eighth-mode SIW (EMSIW) [12,13], which are used to develop compact MIMO antennas. In [9][10][11][12][13], the MIMO antenna utilized HMSIW, where, except [11], all others used rectangular cavity, whereas [11] employed a circular cavity. Furthermore, these MIMO antennas used slots in the cavity except [13], where a rectangular patch antenna was parasitically excited using HMSIW.…”

“…The QMSIW was used to develop MIMO antennas [14][15][16], where the bandwidth enhancement [14,16] and multiband [15] operations were adopted in the designs but at the expense of reduced isolation as compared to the FMSIW [6] or HMSIW [9][10][11][12][13]. However, the sizes of the FMSIW, HMSIW, and QMSIW designs are large compared to the microstrip antennas.…”

“…In earlier work [5], a rectangular slot was used in the ground plane for decoupling purposes to achieve high isolation of 30 dB, and in the latter case [18], no extra decoupling network was used, and a minimum isolation of 18.5 dB was achieved. The SIW MIMO antennas [9][10][11][12][13][14][15][16][17][18][19][20] were developed without considering the space-constrained smartphone scenario, where edges and corners are the only space available for antenna placement [21][22][23][24][25][26][27][28][29]. Therefore, it requires a careful antenna design and placement strategy to fulfill space-related constraints in such a scenario.…”

“…Furthermore, keeping mutual coupling and envelope correlation coefficient (ECC) between antennas below threshold levels [30] is more challenging, especially in a multiantenna environment. The MIMO antennas utilized the SIW via walls [6,11,12], pattern diversity [9], and polarization diversity [13] to achieve isolation; however, in [5], neither via wall nor pattern or polarization diversity was used. Therefore, an extra decoupling network (DN) was employed at the cost of introducing additional design complexity.…”