Frequency Tunable All-Port Reflectionless Nonreciprocal Bandpass Filter Using Spatiotemporal Modulated Resonators

This paper presents compressive analysis and design of a frequency tunable, all-port reflectionless nonreciprocal bandpass filter (NR-BPF) based on spatiotemporal modulation. All-port reflectionless NR-BPF response is achieved by using power division/combination networks together with two identical branches of progressive phase-shifted sinusoidal modulated filters. To provide deeper insight, analytical S-parameters equations have derived using spectral admittance matrices that incorporate time-invariant and time-varying elements. For experimental validation, a microstrip line reflectionless NR-BPF prototype is designed and fabricated. The measured results demonstrate 1:1.225 frequency range, input/output return losses better 12 dB in entire measured frequency range and reverse isolation exceeding 20 dB.