  The digital signal processing has greatly simplified the process of phase
noise measurements, especially in oscillators, but its applications are largely
confined to the frequencies below 400 MHz. We propose a novel transpose
frequency technique, which extends the frequency range of digital noise
measurements to the microwave domain and beyond. We discuss two basic
variations of the proposed noise measurement technique, one of which enables
characterization of phase fluctuations added to the passing signal by the
particular microwave component, for example by an amplifier, while another one
is intended for measurements of phase fluctuations of the incoming signal
itself.
