Phase shifter for fine tuning a microwave applicator

A phase shifter for shifting the phase angle of microwaves traveling in a waveguide of a microwave circuit. The phase shifter includes a dielectric plate which has first and second parallel surfaces, a distal edge, a proximate edge, a leading edge, and a trailing edge where each of the edges defines the outer bounds of the first and second parallel surfaces. The dielectric plate is shaped like a parallelogram lacking any right angles and is made of a microwave low loss dielectric material such as polystyrene or polytetrafluoroethylene. The height of the dielectric plate is less than one half the height of the waveguide side wall and the length is less than one guide wavelength long. The phase shifter fine tunes a resonating microwave circuit and provides approximately three-quarters of an inch adjustment of microwave circuit length.