Cascade Connection of 90-Degree Phase-Shift Networks

A method of connecting 90-degree audio phase-difference networks for use in selective-sideband transmission and reception is shown, whereby an over-all performance is obtained which is analogous to the cascade operation of conventional filters. Three networks are required to obtain twice the rejection in decibels of one. For best results two of the networks must be accurately matched. The cascade connection may either be used with three identical networks to deepen the rejection obtainable with one network over the design range, or it may be used with two similar and one dissimilar network to extend the frequency range over which a given rejection may be obtained.