Non-reciprocal balanced bandpass filters with quasi-elliptic response

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Simpson, Dakotah
Vryonides, Photos
Nikolaou, Symeon
Psychogiou, Dimitra
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Institute of Electrical and Electronics Engineers (IEEE)
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This paper reports on the RF design and practical development of a non-reciprocal balanced bandpass filter (BPF) that exhibits a highly-selective quasi-elliptic response in the forward direction of propagation that is shaped by four transmission poles and two transmission zeros (TZs). By modulating some of the filterâ s resonators with phase-progressed AC signals, a non-reciprocal response is obtained in the differential mode. Its common-mode is also highly suppressed due to the incorporation of a balanced network that results in two additional TZs and resistive loss that are unique to the common-mode. The filter order can be increased by cascading additional resonators. For validation purposes, a microstrip prototype centered at 725 MHz was designed, manufactured, and measured. It showed a high isolation in the differential-mode reverse transmission of up to 62.1 dB. Moreover, the common-mode was suppressed by over 45 dB in a bandwidth greater than one octave.
Balanced filter , Bandpass filter , Isolator , Microstrip filter , Non-reciprocal filter , Non-reciprocity
Simpson, D., Vryonides, P., Nikolaou, S. and Psychogiou, D. (2022) 'Non-reciprocal balanced bandpass filters with quasi-elliptic response', IEEE Transactions on Circuits and Systems II: Express Briefs. doi: 10.1109/TCSII.2022.3202860
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