Compact dual-band bandpass filter using complementary hook-shaped resonators for WLAN applications

Based on the double resonant properties of the complementary hook-shaped resonator (CHSR), a novel miniaturized dual-band microstrip filter is proposed for WLAN operations. The filter, which is only 0.067 λ0 × 0.084 λ0 in overall dimen- sions, is composed of two opposite CHSRs and modified T-shaped feed-lines. Two hook-shaped strips generate two respective passbands, independently. The proposed filter is found to have two transmission zeros around the high resonances for improved selectivity. To verify the proposed method, a dual-band filter is implemented and measured, and the measurement results agree well with the simulated data.