A Precision Analog Duplexing Phase Shifter

This paper describes an analog ferrite phase shifter that provides unlimited phase shift with uniformly low hysteresis and a dispersionless phase shift vs. frequency characteristic. The phase shift angle has a simple mathematical relationship to the driving current values, and is essentially independent of the shape of the magnetization curve of the ferrite material or its variation with temperature. The amount of ferrite material needed for phase shifting is only enough to provide 180 degrees of differential phase shift, and consequently the insertion loss is lower than conventional approaches. An additional 90° nonreciprocal differential phase shift section allows a duplexing function to be incorporated in the unit. Finally, the geometry is very convenient for liquid cooling, permitting operation at high average power levels.