Complex LO waveforms for wideband systems: Some frequency-converter measurement implications

Systems containing frequency-conversion stages using complex Local Oscillator (LO) waveforms, sometimes under the heading of compressive sampling, have been proposed for general wideband communications, 5G applications (large-scale MIMO), signal intelligence and for other purposes. The characterization of the converters used in those applications can be critical for link budgets but those measurements can be complicated by the LO spectral distribution. Aside from the expected waveform dependence of linearity, image response complications and converter operating state questions can lead to multiple dB (or even 10s of dB) variations in the more small-signal-esque conversion efficiency and noise power measurements when taking into account only average or peak power.