PURPOSE: To obtain a characteristic stable for a long period without provision of a mechanical turning part by selecting microwave signals different from the polarized wave forms with an electronic operation.

CONSTITUTION: The selection of the state of 1st and 2nd amplifiers 5, 7 and 1st and 2nd phase shifters 6, 8 is controlled selectively and a signal in response to either a vertically polarized wave or a horizontally polarized wave made incident on a circular waveguide 1 from a synthesizer 9 is outputted, and a signal in response to either a right circularly polarized wave or a left circularly polarized is outputted. Thus, a signal different from a polarized wave form is selected and received by the electronic operation. Thus, no mechanical turning part is required and a stable characteristic is obtained for a long period.