On downconverter noise characterization for LO waveform sensitivities

Downconverter noise behavior can have a dependence on LO waveform details in some circumstances and may be of particular interest in mm-wave/sub-THz applications where multiplied LO noise can be large. A pseudo-systematic characterization process may help in the evaluation of these effects. A composite LO based on summing in the 2
^nd
and 3
^rd
harmonics with controllable phase and amplitude, additional tones for discrete evaluation and coupled waveform monitoring are part of the proposed hardware construct. Repeatabilities ~< 1 dB for converters operating to 330 GHz were observed. In example measurements, topological effects on the waveform dependence were noted as were similarities between a millimeter-wave converter with a large LO multiple and simple diode-based fundamental mixers.