Design of hairpin bandpass filter based on periodic grooves

Abstract

Filter is an important part of wireless communication system, but parasitic passband is produced because of the periodic characteristics of microwave resonant structure. To solve this problem, periodic grooves are embedded in the outer edge of the coupling resonator of the traditional hairpin filter, and the parasitic passband is suppressed by compensating for the phase velocity between the even-mode and the odd-mode. The filter designed in this paper has a center frequency of 2. 6GHz and a bandwidth of 240 MHz. Four periodic square grooves are embedded in each resonator. Simulation results show that the filter can suppress the parasitic passband by -59dB.