Broadband adjustable phase modulation circuit

Claim 1

A phase modulation circuit connected between an input terminal and output terminal comprising in combination: first, second, third, fourth and fifth 90° couplers each having a pair of input ports and a pair of output ports; first, second, third and fourth adjustable gain amplifiers each having a control terminal, an input port and an output port; an in-phase combiner having an output port coupled to said output terminal and a pair of input ports; the input ports of said first 90° coupler being connected to said input terminal and a terminating impedance respectively, one of the pair of output ports thereof and a terminating impedance being connected respectively to the respective input ports of said second 90° coupler, the other of the pair of output ports of said first 90° coupler and a terminating impedance being connected respectively to the respective input ports of said third 90° coupler, the output ports of said second 90° coupler being connected to the input ports of said first and second amplifiers respectively, the output ports of said third 90° coupler being connected to the input ports of said third and fourth amplifiers respectively, the output ports of said first and second amplifiers being connected respectively to the input ports of said fourth 90° coupler, the output ports of said third and fourth amplifiers being connected respectively to the input ports of said fifth 90° coupler, one of the pair of output ports of each of said fourth and fifth 90° couplers being connected to said input ports of said in-phase combiner, the other of the pair of output ports of said fourth and fifth 90° couplers being connected respectively to respective terminating impedances; and a control means coupled to the control terminal of each amplifier for controlling the gain thereof and for thereby controlling the phase shift of signal between said input terminal and said output terminal.