Making phase and group delay response measurements on mixers and frequency converters has traditionally been a difficult and complicated process, requiring either modulated-signals (and demodulation), two-tone signals (a special form of modulation) or a system with a reference or re-converting mixer. This paper presents a method to measure the phase response of a mixer on a VNA using a novel phase-measurement method which can measure the input and output phase response independently, computing the transfer response directly. This method relies on a VNA system which utilizes swept-frequency phase-coherent sources and receivers to maintain a common phase reference. A software phase-locking method allows it to operate on frequency converters which have an in-accessible embedded LO, along with a well established method of calibration.
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