Compact microstrip bandpass filter with wide stopband

Abstract

A compact microstrip bandpass filter using a meandering uniform impedance resonator and a meandering stepped-impedance resonator is proposed. The two resonators have the same fundamental resonant frequency and different higher order resonant frequencies for a good stopband rejection. Furthermore, input and output enhanced couplings not only reduce the insertion loss but also improve the stopband rejection. For a rejection better than 20 dB, the proposed filter does not show any spurious passbands till 8.54 f0, where f0 is the fundamental frequency.