Low-Profile Filtering Antenna With Wide Stopband Using Dual-Mode Rectangular SIW Cavities

A low-profile filtering antenna with a wide stopband based on substrate integrated waveguide (SIW) is presented in this article. First, a five-pole bandpass filter using a cul-de-sac topology scheme with two finite-transmission zeros (FTZs) is proposed. The SIW filter which consists of three single-mode cavities using TE101 mode and a dual-mode cavity using TE201 and TE103 mode achieves a wide stopband due to the suppression of TE102, TE202, and TE104 mode. Then a cavity-backed slot antenna is designed so that its bandwidth is narrower than that of the filter, thus making it behave as a last-order resonator. With a center frequency of 10 GHz and a fractional bandwidth of 4.03%, the antenna has good stopband performance and achieves a gain of 7.8 dB in terms of a flat gain profile.