A phase reference system for a phase-sensitive receiver is shown that provides an output signal which can be used for phase calibration of a frequency-converting device under test. The phase reference system has a first frequency generator that generates a first generator signal with a first generator frequency fg1 and a second frequency generator that generates a second generator signal with a second generator frequency fg2. The first and second generator signals are fed to a multiplier. The multiplier process the signals and outputs first, second and third spectral line data.