SIW Based D-Band Single and 2 × 2 MIMO Elliptically Tapered Slot Antenna

In this paper, the substrate integrated waveguide (SIW) based single and
$2\times 2$
multiple input multiple output (MIMO) elliptically tapered slot antennas (ETSA) have been demonstrated at the D-band. The width of the coupling SIW line is selected to operate at the TE10-mode within the frequency range of interest. The elliptically tapered opening is designed in front of the upper and lower metal layers at the radiating end of the SIW line. The outer sides of elliptically tapered metal extensions are corrugated to improve the impedance matching. For measurement, three separate SIW based transitions working at different frequency ranges are integrated with single SIW ETSA and named as Ant-1, Ant-II, and Ant-III. A setup was constructed for far-field measurements within the laboratory where only the 2D radiation patterns and gains can be measured. The Ant-I, Ant-II, and Ant-III prototypes achieved a measured
$\vert \text{S}_{11}\vert < -10$
dB of 20 GHz (110–130 GHz), 28.6 GHz (130–158.6 GHz) and 16 GHz (154–170 GHz) with peak gains of 12.85, 12.86, and 10.4 dBi, respectively. For
$2\times 2$
MIMO versions, the S-parameters, and condition number for line-of-sight scenario were measured.