Null Technique for Precision RF Phase Shift Measurements

A dual channel IF substitution null system is developed for precision phase shift measurements and standards in frequency ranges of 1 MHz to 1 GHz. A particular programmable IF phase shifter equipped with a calibrated phase monitor is used as a phase reference standard. High sensitivity nature of the null technique provides accurate measurements to the DUT even with large attenuation. Measurement resolutions of 0.002 deg., 0.006 deg., and 0.023 deg. were obtained for DUT with attenuation of 20 dB, 40 dB, and 60 dB, respectively, at 1 GHz.