Wideband millimeter-wave SIW cavity backed patch antenna fed by substrate integrated coaxial line

In this paper, a wideband substrate integrated waveguide (SIW) cavity backed patch antenna element is proposed for high-gain arrays at millimeter-wave bands. By compensating the inductance of the feeding metallic via with a capacitive ring slot on the ground plate, an additional resonance is introduced to the patch mode to expand the bandwidth. To suppress the backward radiation from the slot and enhance antenna gain, a back SIW cavity is designed. Moreover, the low-loss and compact substrate integrated coaxial line (SICL) is employed as the feeding line. The simulated −10/−15 dB impedance bandwidth of the element is 14.9%/11.6% (both at 43 GHz). The introducing of the back cavity and SICL makes the element suitable for large wideband high-gain millimeter-wave arrays with excellent front-to-back ratios (FBRs) and stable radiation patterns on printed circuit boards (PCBs). As an illustrative example, a 2×2 corporately-fed sub-array is developed and tested. The −10 dB impedance bandwidth is 11.7%, and the peak gain is 11.4 dBi with a simulated radiation efficiency of 88% and measured FBR of above 20 dB.