Design of Compact Microstrip Stepped-impedance Resonator Bandpass Filters

This paper presents the resonator bandpass filter design using the proposed stepped-impedance resonator technique. The proposed resonator is consisted of a quarter wavelength coupler with the stepped-impedance connected at the end of the lines. Each ports have a step impedance feed line to adjust the impedance of filter closed to the characteristic impedance Z0. This resonator can reduce the spurious response at 2f0 and 3f0. The experimental results and designs of all types are 0.9 GHz to implement bandpass filters. This filter can suppress the second and third spurious response that both the theoretical and experimental performance is presented.