A coupling theorem for matched symmetrical two-branch four-port networks

In this paper a theorem is derived which relates to the coupling of matched lossless symmetrical four-port networks of the twobranch type. In particular it is assumed that the two in-line and two branch-line networks are identical and that these pairs of networks differ identical two-port matching networks are connected at each of the fourports so that the complete device is matched at the frequencies , ,then the coupling will be the same at all of these frequencies and dependent only on the admittance ratio .