Quasi-constant Phase Shifter by Stable Band-Limited Non-foster Circuits

A quasi-constant phase shifter enabled by band-limited non-Foster circuits is proposed in this paper. The proposed circuit provides wide band phase shifting with phase mismatch < 2.7°, amplitude mismatch < 1 dB over 10 GHz bandwidth, while supporting flexible phase adjustability. The band-limited non-Foster circuit structure is presented by using two side transistors to compensate the effects of cross-coupled transistors in Linvill’s structure [1], which shows positive capacitance at low frequencies and negative capacitance at high frequencies. To analyze the stability of band-limited non-Foster circuits and guide design optimization, Impulse Response Function (IRF) method is proposed, which takes into account circuit frequency dependent effects, distinct from conventional methods.