An Arbitrary Phase-Difference Hybrid Coupler with Enhanced Bandwidth

The existing arbitrary phase difference hybrid couplers usually have limited bandwidths due to the much more complex requirements for implementing non-standard phase difference. To effectively extend the bandwidth of a two section branch line coupler with arbitrary phase difference, a coupled line section is utilized to replace the middle branch. For validation, two 3 dB couplers which provide 45 degrees and 135 degrees phase differences were designed and fabricated. They were measured to achieve wide bandwidths of 33.7% and 25% respectively.