Compact Self-Quadruplexing SIW Cavity-Backed Slot Antenna

This communication presents a compact self-quadruplexing substrate integrated waveguide (SIW) cavity-backed slot antenna for quad-band communication services. The proposed antenna uses four V-shape slots of different lengths for radiation. Each slot is backed by a quarter-mode SIW cavity, which is excited by a 50 Ω microstrip line. The band positions can be independently controlled. A prototype antenna with the radiating frequencies 8.19, 8.8, 9.71, and 11 GHz is fabricated. The antenna has more than 22 dB measured isolation among the ports. Measured maximum gains of the antenna are 5.5, 6.9, 7.47, and 7.45 dBi at their operating frequencies. It has a cross polarization level of below -24.7 dB and a front-to-back ratio of more than 18.2 dB in all the bands.