Mixer Residual Phase Noise Measurements Using Clock-locked DDS Sources and Receivers

Methods for residual measurements on mixers are difficult and require at least one other mixer making it difficult to separate the residual effects between them. Here we introduce a novel scheme that uses a system completely clocked off a single reference oscillator using pairs of DDS sources to produce an input and LO signal as well as a third DDS source to re-convert the mixer output We show the close-in phase noise is largely canceled with this method resulting in a good measure of the mixer residual phase noise somewhat independent of the raw phase noise of the DDS sources. This improvement can also be shown for close-in residual measurements of amplifiers.