In-band phase deviation minimization method for wideband tunable phase shifter

This article provides a novel approach to analyze and design wideband tunable reflection-type phase shifter (RTPS) with low in-band phase deviation (IBPD) error. The proposed RTPS consists of coupled lines where through and coupled ports are terminated with varactor diodes. The coupled lines can minimize the parasitic elements of varactor diode to achieve high phase shift range (PSR). In addition, the measured frequency-dependent capacitance of varactor diode was used in the analytical analysis to obtain minimum IBPD error and high PSR. For experimental demonstration, phase shifter was fabricated at the center frequency of 2.5 GHz. The measured results show that the fabricated circuit achieved 126.85° PSR with ±6.48° IBPD error for 500 MHz bandwidth (BW). In addition, the measured maximum insertion loss variation and input/output return losses are within ±0.34 dB and higher than 16.85 dB within 500 MHz BW, respectively.