The present invention relates to a method for characterizing at a given frequency reflected waves of a frequency translating device having at least two ports, whereby information is available on the phase of a local oscillator driving the frequency translating device. The method comprises the steps of—applying at the at least two ports at least a tone at said given frequency and tones at said given frequency offset by the local oscillator signal frequency,—rotating the phase of the applied tone at said given frequency or exploiting a phase rotation of the local oscillator signal,—measuring at said given frequency amplitude and phase of reflected waves at the at least two ports and measuring at said given frequency and at said given frequency offset by the frequency of the local oscillator signal amplitude and phase of incident waves at the at least two ports,—determining parameters for a model of the frequency translating device by relating the amplitude and phase of the reflected waves to the incident waves, taking into account at least the local oscillator signal phase.