A wideband 3 decibels arbitrary phase difference branch line coupler

A wideband 3 dB branch line coupler with arbitrary phase difference between output ports is proposed. The wideband properties in both amplitude and phase are achieved by utilizing /4 coupled line sections. By designing different even and odd impedance of the coupled line matched in different ports, small phase imbalance can be achieved. For validation, two 3 dB couplers with different phase differences (60 degrees and 120 degrees) were designed and fabricated. They were measured to exhibit wide bandwidths of 40.2% and 44.6%, respectively.