Continuously Tunable True-Time-Delay Phase Shifter With Extended Tuning Range

A continuously tunable true-time-delay phaseshifter topology based on switchable varactor-tuned transmission lines is presented. By introducing p-i-n diodes to switch different varactor-tuned transmission lines, the phase shift tuning range can be doubled compared with the conventional design, which results in 50% size reduction. For verification, two cascaded four-unit and eight-unit microstrip phase shifters are designed and fabricated on a 0.787-mm-thick Rogers RT/Duroid 5880 substrate with epsilon(r) = 2.2 and tan delta = 0.0009. The measured microstrip phase shifts of the four-unit and eight-unit phase shifters are about 107 degrees and 191 degrees at 4 GHz, respectively, with insertion loss of less than 2.4 and 3.6 dB. The return loss is better than 15 dB from 0.5 to 4.65 GHz for all states.