Balanced Nonreciprocal Bandpass Filter With Common‐Mode Reflectionless Characteristics

Abstract In this paper, a common‐mode (CM) reflectionless balanced nonreciprocal bandpass filter (BPF) based on the time‐modulated resonator is presented. In order to reduce the interference caused by reflected CM noise on the neighboring circuit and the impact of radiation emission interference caused by CM noise on system stability, a novel design concept for a CM reflectionless balanced nonreciprocal BPF is realized by independent loading CM absorption branches. The CM absorption branch, when combined with the filtering section, achieves effective absorption of CM noise and does not affect the nonreciprocal transmission characteristics of the differential‐mode (DM) signal. The paper derives the DM and CM scattering parameters to elucidate their respective nonreciprocal transmission and absorption characteristics. Furthermore, the selection of modulation parameters is guided to expedite the circuit design process. To validate the concept experimentally, a 1.5‐GHz microstrip prototype is designed, simulated, manufactured, and characterized.