A novel class of compact dual-mode coaxial filter using stepped impedance resonators

Dual-mode cavity filters have been widely used in wireless communications systems due to their advantages of small size, low loss and high power handling capability. In this paper, a novel dual-mode coaxial bandpass filter with stepped impedance resonator (SIR) configuration is proposed. The resonator that supports the TEM mode can exhibit two resonances. By combining multiple resonators, higher order filters with narrowband response can be realized within compact structure. Besides, a 4th order filter is designed, theoretical analysis and simulation results prove the fesibility of the proposed class of filters.