Multisection broadband impedance transforming branchline quad hybrid suitable for MMIC realisation

A two section impedance transforming branchline hybrid is reported. Such a hybrid is a very useful component for microwave monolithic integrated circuit implementation of a variety of circuits. It is shown that such a hybrid can be optimised to yield a wide operating bandwidth as well as practically realisable branchline impedances. Both equal and unequal power division with 90 degrees relative phase shift are feasible. Computed and measured results show that a 50-35 Omega two section optimised hybrid with equal power division has 30% bandwidth over which the power balance is better than 0.5 dB. The return loss and isolation are better than 20 dB over this bandwidth.