Low Delay and Loss Variation Reflection Type Phase Shifter with Sequentially Controlled Varactor Diodes

This paper presents a full 360° reflection type phase shifter (RTPS) with low delay and loss variations. The proposed RTPS has reflective loads composed of two complementary resonators for a full 360° phase shift. Varactors of two resonators are controlled to have a phase shift. To minimize the loss and delay variations, the bias voltages of varactors are sequentially controlled, and one voltage is swept while the other is fixed. This method gives much lower delay and loss variations compared to a conventional simultaneously tuning method by avoiding combinations of bias voltages with high delay and loss variations. The proposed RTPS using the sequentially tuning method operates at 3.7 GHz over 600-MHz bandwidth. The measured phase range is 377° and the group delay and insertion loss variations are 250 ps and 1.3 dB respectively over the bandwidth. The return loss is more than 15 dB for all bias states.