Semi-Lumped Cross-Coupled Non-reciprocal Bandpass Filter for 5G Communications

This paper is based on a design and characterization of a fourth-order semi-lumped cross-coupled band pass filter implementing non-reciprocity at the mid band frequency of 1 GHz using spatio-temporal modulation applied on resonators. This work methodically combines static and time-modulators resonators using direct coupled lumped elements with an additional source-load cross-coupled structure. The former generates the non-reciprocal response while the latter manifests a highly selective passband. The concept is first of its kind and the simulated non-reciprocal filtering isolation response show enhanced skirt frequency characteristics in addition to a moderately high reverse isolation within the passband in the backward direction. The insertion loss, return loss, and isolation achieved are 3.4 dB, >15 dB, and >13 dB, respectively. This non-reciprocal filter configuration can be equipped in 5G FR1 bands owing to the highly selective response.