Tunable differential phase shifter with low in-band phase deviation error over wide phase shift range

In the brief, a tunable differential phase shifter (D-PS) which features the characteristics of low in-band phase deviation error, wide phase shift range (PSR), and compact structure is presented. The main and reference lines of the D-PS are constructed by reflection-type phase shifters (RTPSs). In the main line, the reflection load is composed of two varactors and a short-circuited stub in parallel connection. While the reflection load in the reference line is consisted of an inductor paralleled with a short-circuited stub. Design equations of the proposed D-PS is derived, and the influences of the reflection loads on the performances of the D-PS are investigated. For validation, a prototype operating at 2 GHz is designed. Measurement results show that the 10-dB impedance matching bandwidth is 20.7 %. During the tuning, a PSR of 243 degrees is obtained and the bandwidth for phase dif-ference error <10 degrees is 12.1 %.