Variable linear phase-shifting network

A network is described enabling the variation of a linear phase characteristic by a single terminating resistor. The network is based on one form of Bode´s variable equaliser, the theory of which is briefly presented. Design equations are developed for evaluating the elements of the network. It is shown that variation of the basic loss of the network provides another means of controlling the slope of the resulting phase characteristic. The starting point in the design procedure is the formulation of a realisable linear phase characteristic. This characteristic is realised by two constant-resistance bridged-T networks and an all-pass structure connected in cascade with a variable terminating resistor. Experimental results are given and close agreement with theory is demonstrated.