Design of a Novel Filtering Antenna Using Waveguide With Enhanced Stopband Attenuation

Abstract

This work details a novel type of waveguide filtering antenna (filtenna) with a two-post design for use in wireless satellite communications and radar systems. The proposed design incorporates the filtering and radiating capabilities in one small, rectangular, rigid system to overcome the constraint of conventional design methods which demand distinct filtering and radiating elements. The design uses a rectangular waveguide (WR-90) with two metallic posts, in two configurations inline and rotated offset which allows accurate control of the transmission zeros (TZs), high quality factor and stopband attenuation. This novel approach eliminates the requirement for the usual coupling irises to control bandwidth. The inline filtenna has a filtering bandwidth of 1.02 GHz at the X-band and a radiation bandwidth of 0.20 GHz. In contrast, the rotated-offset filtenna has been demonstrated at 9 GHz to 9.5 GHz, with a radiation bandwidth of 0.5 GHz. The simulated and measured results are in good agreement, with maximum gains of 7.05 dBi in the inline and 6.15 dBi in the rotated-offset orientations, and overall efficiency greater than 90 %. The inline filter has a reflection coefficient of less than -19 dB over the 10.6 GHz to 11.25 GHz range, which guarantees a good impedance match. The rotated-offset filtenna has wideband characteristics whose impedance is closely matched in the 8.92 GHz to 9.5 GHz operating band. The final design combines filtering and radiation capabilities in a compact form, increasing frequency selectivity and efficiency. These results emphasize the suitability of the suggested design for radar and satellite systems requiring small size and high-performance RF components.