Advancing Bandpass Filters: Spatio-Temporal Modulation with Coupled Line Sections for Non-Reciprocal Behavior

This paper presents a microstrip non-reciprocal 3
^rd
order coupled line bandpass filter by applying time-modulated waves to the half-wavelength resonators. The varactors, loaded into each half-wavelength resonators, are modulated with sinusoidal signals to generate time-varying capacitance superimposed on a nominal capacitance effectuated by reverse-biased DC voltages. By properly introducing progressive phase difference between the modulation waves, circuit analysis shows that non-reciprocal filtering isolation response can be achieved. To validate the suggested approach, a microstrip 3rd-order non-reciprocal bandpass filter based on parallel coupled lines at 2.4 GHz is designed and simulated. Advanced electromagnetic simulation tools were used to run extensive simulations in order to show the effectiveness of the suggested design. The simulated outcomes demonstrate insertion loss less than 4 dB, return loss greater than 10 dB, isolation more than 20 dB with good selectivity and stop band rejection suitable for WLAN applications.