U-band finline bandstop filter with dual-mode resonator

Abstract

In this work, multi-mode resonator technology is applied to finline bandstop filter (BSF) to improve its performance. A finline BSF with two transmission zeros in the stopband is realized by using a new kind of dual-mode finline resonator proposed in this paper. The bandwidth of the designed filter is clearly broadened to three times that of the traditional finline BSF without enlarging its size. Its measured bandwidth under 20 dB rejection is about 600 MHz and the insertion loss in the passband is below 0.4 dB including the insertion loss of two finline-to-waveguide transitions. There is a good agreement between the simulated and measured results.