Compact Wideband Bandpass Filter Using Miniaturized Staircase Interdigital Resonators

This paper introduces a compact wideband bandpass filter (WBPF) based on new miniaturized staircase interdigital resonator. The proposed filter operates at a center frequency of 2.44 GHz with a wide fractional bandwidth of 62.5% and low insertion loss equals to 0.5 dB. The filter is implemented on a Duroid substrate with 10.2 relative dielectric constant and 1.27 mm thickness. In comparison with conventional quarter-wavelength interdigital resonators, the proposed staircase resonator offers higher compactness and 28% size reduction with wide passband responses. The reported WBPF occupies a small area of 6.5 mm × 8.5 mm with an effective area of just 0.025λ²g0. Moreover, it has key merits of simple design and implementation, easy integration, and wide stopband bandwidth. The proposed filter is successfully analyzed, designed, fabricated, and measured. Experimental results have shown good agreement with simulated ones.