An L-band SiGe HBT reflection-type phase shifter using active loads with varactor-tuned LC-resonators and RC-feedback circuits

A new reflection-type phase shifter using active loads is presented. The active load is based on a common-emitter configuration employing varactor-tuned LC-resonators in the load circuit and parallel RC circuits in the series feedback circuit. The varactor-tuned LC-resonator provides a wide relative phase shift and the RC-feedback circuit produces negative impedances for improving an insertion loss variation. The implemented phase shifter using Si varactor diodes with a capacitance ratio of 2.5:1 and SiGe HBTs with an f_t of 25GHz has achieved a maximal relative phase shift of 256°, an insertion loss variation less than 3dB and return losses better than 9dB at 1GHz.