A novel broadband 90° phase shifter

The 90degphase bit of high-pass/low-pass phase shifter suffers from large phase error compared to the smaller phase bits. To improve the phase error performance, this work develops a network that provides a differential phase of 90degwith a small phase error (< plusmn2deg) over a large bandwidth. Compared to other work focused on this bit, the new network shows theoretical bandwidth of 88% (2.6:1) while keeping the return loss better than 17 dB. The experimental result shows a plusmn 2.5degbandwidth of 102% (3:1), a return loss better than 12 dB and an amplitude variation less than 0.5 dB from 0.94 GHz to 2.89 GHz.