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 $\pmb{\epsilon}_{\mathbf{r}}=\mathbf{2.2}$ and $\pmb{\tan\delta}=\mathbf{0.0009}$ . For a I-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.