Co-channel interference suppression apparatus

Apparatus to suppress an interference signal on the same frequency as a desired signal, comprising:

• a) a sum and difference hybrid having a first and second input port and two output ports, one a sum port and the other a difference port, the first and second input ports receving signals from a first and second antenna respectively of a two antenna array directed at the desired signal source,
• b) a combiner having a first and second input port and one output port the first input port of the combiner being connected to the hybrid sum port and the second input port of the combiner being connected to the hybrid difference port,
• c) means for introducing a change in amplitude in the signal from one of the output ports of the hybrid to permit the interference signal component of said signal from the hybrid to be made equal in magnitude to the interference signal component of the signal from the other output port of the hybrid, and
• d) means for introducing a change in phase of substantially 90.degree. in one of the output signals from the hybrid to permit the interference component of that signal to be placed in phase opposition with the interference component of the other output signal from the hybrid to produce cancellation of the interference signal components when the hybrid output signals are added in the combiner, said means for introducing a change in phase includes a variable phase shifter, a fixed 90.degree. phase shifter, a switchable 180.degree. phase shifter in series with the 90.degree. phase shifter to produce in combination a plus 90.degree. total phase shift when the 180.degree. phase shifter is switched out of the circuit and a -90.degree. phase shift when the 180.degree. phase shifter is switched into the circuit.