Phase Measurement of RF Devices Using Phase-Shifting Interferometry

A novel measurement technique is introduced for high-resolution phase measurements of RF devices. It is based on phase-shifting interferometry and is, therefore, fairly independent of the absolute magnitude of the measured RF signal, as demonstrated by measurements. A low-cost vector network analyzer (VNA) working up to a frequency of 150 MHz is presented using a multiple output direct digital synthesizer and low-cost scalar detectors. Furthermore, a wideband RF synthesizer architecture capable of generating multiple synchronized phase adjustable RF signals is developed. A homodyne reflectometer based on RF interferometry and the presented synthesizer is introduced. Accuracy limitations due to nonlinear power detectors and harmonics using the homodyne approach are demonstrated by measurements. A heterodyne reflection test set using the novel phase measurement technique at a constant IF is developed to solve these accuracy limitations. The performances of both interferometric reflection test sets are verified by measurements and compared to commercially available VNAs.