A flexible design procedure for microstrip planar disk 3 dB quadrature hybrids

A flexible design procedure is presented for the recently synthesized microstrip planar disk 3-dB quadrature hybrid. The design approach adopted uses external two-port matching networks connected at each of the device coupling ports. It is shown that a four-port device having a given disk radius and the necessary hybrid symmetry can be designed to operate as a 3-dB quadrature hybrid over a wide range of frequencies simply by an appropriate positioning of the coupling ports and an appropriate choice of matching network. The design procedure has been verified experimentally by the successful synthesis of two new 3-dB quadrature hybrid devices