A novel microstrip triple-mode wideband bandpass filter using radial-line stubs

This paper presents a novel approach for designing microstrip triple-mode wideband bandpass filter with good selectivity. The triple-mode resonator is composed of an open-ended microstrip line with length of half-wavelength (λ/2) and two center loaded radial-line stubs. The mode characteristics of the resonator are discussed. Also, an equivalent lumped circuit is proposed, including the parameters extracting. To verify the proposed method, an experimental filter is implemented. The measured results exhibit good agreement with the simulation.