Compact Dual-Band SIW Vertical Integrated Filtering Antenna for mmWave Applications

In this letter, a novel dual-band cavity-backed slot filtering antenna is proposed. The dual-band operation is achieved by exciting the higher-order modes TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">110</sub> and TM<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">210</sub> of the circular substrate integrated waveguide (SIW) cavity. By vertically integrating two cavities, the second-order filtering response is realized under a compact dimension. The upper cavity can also serve as a slot-loaded common radiator. Notably, two slots are symmetrically distributed, which achieves upper-band radiation while improving the cross-polarization discrimination (XPD). The measurements are in good agreement with the simulations, demonstrating the impedance bandwidths of 4.4% (24.6-25.7 GHz) and 3.2% (36.5-37.7 GHz), along with the maximum broadside gains of 5.1 dBi and 7.7 dBi for the lower and upper bands with high XPD (more than 35 dB), respectively.