Highly Selective and Compact Filtering Antennas Using Dual-Mode SIW Resonators

Abstract

A novel class of compact and highly selective filtering antennas controlling two finite position transmission zeros (TZ) are presented. The filtering antennas are composed of a substrate integrated waveguide (SIW) filtering doublet and a wideband cavity backed slot antenna (CBSA). Design guidelines are presented to implement bandpass filtering antennas with TZ either: above, below or on opposite sides of the passband. The TZ location is highly flexible relative to the passband and is entirely determined by the input feed offset and via position. Stand-alone devices demonstrating the three via arrangements are presented around 16 GHz. All devices demonstrate a flat passband gain around 5 dB with a single element, direct control over the TZ position, high passband roll-off and out-of-band attenuation, and low cross-polarization. Compared with the state-of-art SIW filtering antennas, the fabricated devices demonstrate the highest combined bandwidth, passband roll-off and out-of-band attenuation. Additionally, the device with TZ on either side of the passband is sequentially rotated in a 2x2 topology to form a right-handed circularly polarized filtering array with a flat passband gain around 9 dB, retaining the high selectivity.