Continuously Tunable True-Time-Delay Phase Shifter Using Switchable Varactor-Tuned Transmission Lines

This work reports on a continuously tunable true-time-delay phase shifter using switchable varactor-tuned transmission lines. The phase shift tuning range is extended by using p-i-n diodes to switch different varactor-tuned transmission lines without increasing the capacitance tuning range. Two phase shifters are fabricated on a 0.787 mm-thick Rogers RT/Duroid 5880 substrate with εr = 2.2 and tanδ = 0.0009. For a 1-unit phase shifter, the measured phase shift is about 28° at 1 GHz with insertion loss of less than 1.4 dB, and return loss of better than 15 dB. For a cascaded 2-unit phase shifter, the measured phase shift is about 49° at 1 GHz with insertion loss of less than 1.5 dB and return loss of better than 15 dB.