Microwave phase shifting device

Abstract

An improved phase shifting device for varying the phase of the standing wave in a hollow rectangular waveguide is provided which is particularly applicable to microwave cooking appliances. A metallic septum is constructed at the end of the waveguide remote from the microwave source which extends inwardly into the waveguide from the adjacent waveguide end wall parallel to the narrow walls of the waveguide and electrically connects the broad walls of the waveguide, thereby dividing the waveguide into two sub-waveguides, each of which exhibits a cut-off characteristic at the operating frequency. The leading edge of the septum provides a short circuit termination reference point for the waveguide. The moving parts comprise a pair of dielectric plugs, each of which is received in a respective one of the sub-waveguides for selective movement in tandem from a reference position completely within the sub-waveguides to one or more phase shifting positions in which the plugs extend forward of the septum leading edge toward the microwave source. The shift in the phase of the standing wave varies linearly with the extent of forward displacement of the plugs relative to the septum leading edge. The plugs are selectively moved in tandem relative to the reference position in the sub-waveguides to provide the desired phase shift.