A branch-line-type eight-port comparator circuit

A method of constructing an eight-port comparator with four branch-line 3 dB quadrature hybrids is described theoretically and experimentally. A relative bandwidth of up to 20% (for return loss and isolation better than 20 dB) is obtained by addition of simple external circuits. A strong point of the present comparator is that it is manufactured on the same face of a substrate using a planar transmission line such as a stripline or a microstrip line.<<ETX>>