Phase-Shifting Interferometry for RF Phase Measurement

This paper introduces an interferometric technique for the phase measurement of microwave devices. A handheld vector network analyzer (VNA) is presented for HF and VHF applications. A wideband synthesizer with multiple synchronized outputs is developed for extending the frequency range to the microwave band. The phase differences between the output signals can be set digitally with sub-degree accuracy using direct digital synthesizers (DDS). The phase measurement based on the superposition of these phase adjustable signals is fairly independent of the absolute magnitude of the measured signal. Reflection test sets using the introduced RF interferometry for HF/VHF and microwave signals are presented. The accuracy of the phase measurement is verified by measurements.