Wideband and High-Selectivity Dual-Band Filter for Ka-Band Satellite Antennas

A dual-band miniaturized Ka-band filter is presented, taking advantage of transmission in cutoff rectangular waveguides periodically loaded in the E-plane with split-ring resonators (SRRs). High selectivity, wide bandwidth, and high out-of-band rejection are achieved in a compact form factor. The use of SRRs in a waveguide configuration proves to be a valid and promising solution for the design of dual-band filters. The filter is specifically designed for Ka-band, and a prototype was manufactured and its performance measured, providing a reasonably flat transmission at both 20- and 30-GHz subbands. For both bands, the power roll-off rate is higher than 55 dB/decade, translating into a sharper than 10-dB drop per 0.2 GHz in a 38 × 6.6 × 4.5-mm³ device. The filter half-power bandwidth is B20 = 1.1 GHz at 20 GHz (18.4-19.5 GHz) and B30 = 1.2 GHz at 30 GHz (27.8-29.0 GHz).