A Multisection Broadband Impedance Transforming Branchline Quad Hybrid Suitable for MMIC Realization

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 optimized to yield a wide operating bandwidth. Also, practically realizable branchline impedances can be obtained. Both equal and unequal power division with 90° relative phase shift is feasible. Computed and measured results show that a 50 to 35¿ two section optimized hybrid with equal power division has a thirty percent bandwidth over which the power balance is better than. 5dB. The return loss and isolation are better than 20 dB over this bandwidth. Computed results also show that an optimized 50 to 6O¿ impedance transforming hybrid with 3dB unequal power split has return loss and isolation better than 2OdB as well as a bandwidth of thirty percent. The limitations of the theoretical design equations are examined. Varactor tuned hybrid phase shifters are simulated and the relationship between the hybrid impedance transformation ratio r, and the phase shift and attenuation of the phase shifter is examined.