New design of the miniature microstrip stepped-impedance resonator for bandpass filters

This paper describes the resonator bandpass filter design using the proposed microstrip stepped-impedance resonator technique. The proposed resonator is consisted of a quarter wavelength coupler and the square impedance located at the end of the parallel coupled line. Each port has a step impedance feed line to adjust the impedance of filter closed to the characteristic impedance Z_o. This resonator can reduce the spurious response at 2f₀ and 3f₀ by its structure. The experimental results and designs of all type 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.