A Novel Balanced Nonreciprocal Bandpass Filter Based on Stepped-Impedance Resonator and Time-Modulated Resonator
P. Han, Zhan Wang, Haiqiang Liu, Mingyuan Gao, S. Fang · Radioengineering · 2024
A novel balanced nonreciprocal bandpass filter based on the stepped impedance resonator and the timemodulated resonator is proposed in this paper.The balanced nonreciprocal bandpass filter is fabricated on a single PCB board, and the compact structure is achieved through the gap coupling structure of the microstrip resonators.Utilizing the quarter-wavelength transformer and gap coupling structure, good isolation between RF and modulated signals is achieved without adding lumped elements.Relying on the efficient modulation circuit and the half-wavelength stepped impedance resonator's inherent resonance characteristic, an excellent nonreciprocal characteristic of the differential signal and effective suppression of common-mode noise are achieved.A balanced microstrip nonreciprocal bandpass filter operating at the center frequency of 1.5 GHz is designed, simulated, and experimentally verified.The measured reverse isolation is greater than 20 dB with a bandwidth of 48.8 MHz.The measured forward differential-mode insertion loss is 3.7 dB at the center frequency of 1.5 GHz.In the range of 1.2-1.8GHz, the measured common-mode noise suppression is larger than 60.4 dB.