Null Technique for Precision RF Phase Shift Measurements

Abstract

A dual-channel intermediate frequency (IF) substitution null system is developed for precision phase shift measurements and standards in the frequency range from 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 device under test (DUT) even with large attenuation. Excellent measurement resolutions of 0.002°, 0.006°, and 0.023° were obtained for DUT with losses of 20, 40, and 60 dB, respectively, at 1 GHz. Due to its independent and high-precision nature, this system can be used as a validation system as well as a reference standard of a broadband phase shift measurement system.