A Non-reciprocal Third-order Comb Bandpass Filter Based on Spatiotemporal Modulation

In this paper, a non-reciprocal third-order comb bandpass filter based on spatiotemporal modulation is presented. By appropriately introducing a phase shift between the three modulated signals, non-reciprocal transmission between the two ports of the filter is achieved. By increasing the number of resonators, low forward insertion loss and high backward isolation of the filter can be improved. To verify the proposal, a microstrip non-reciprocal third-order comb bandpass filter with a center frequency of 1.0 GHz is designed, simulated and measured. The measured results show that the return loss of the proposed non-reciprocal third-order comb bandpass filter in the working band is less than 15dB, and the minimum insertion loss is 2.6dB; in the meantime, the isolation can achieve 16dB in maximum.