Radio frequency power modification without phase shift

Claim 1

A microwave circuit for controlling the level of radio frequency power without a phase shift comprising: input and output hybrid elements for coupling power into and out of said circuit and into and out of first and second channels for conduction equal amounts of power between said input and output hybrid elements; first and second adjustable phase shift element, in corresponding ones of said first and second channels, for shifting the phase of power travelling therethrough by equal and opposite amounts, whereby the amplitude of power coupled out of said hybrid element may be varied by adjustment of the phase shift, characterized in that: each of said first and second channels consists of a single conductive path for microwave power between said input and output hybrid element wherein each of said first and second paths exclude hybrid elements for splitting power; one of said conductive paths includes a phase shifter set to shift the phase of power passing therethrough by a quantity phi; and the other of said conductive paths includes a fixed phase shifter for shifting the phase of power passing therethrough by one hundred eighty degress and a phase shift element set to shift said phase by an amount equal to one hundred eighty degrees minus phi.