Novel method for millimeter wave phase shifter design using loaded transmission line

A succinct and effective design strategy is presented for millimeter wave frequency phase shifter design. The method aims at achieving minimum phase error around center frequency. Theory analysis shows that up to fourth-order derivative of phase shift with respect to frequency can be 0 at center frequency, which means phase shift is very flat around center frequency. Besides, constant 90° and 180° phase shift can be achieved theoretically. By using the method, the designed 90° and 180° phase shifters have small phase shift deviations. The measurement results show that the designed 90° and 180° phase shifters have better than ±2.8° and ±4.6° phase stability, less than 1.1 dB and 1.48 dB insertion loss, and better than 10 dB return loss from 24.8 GHz to 32.35 GHz respectively.