LO waveform effects on the linearity of sub-THz frequency converters

Abstract

Frequency converters in the sub-Terahertz/sub-millimeter frequency ranges often use high local oscillator (LO) multiples, whether these converters are configured as harmonic mixers or samplers. As such, there can be enhanced dependencies on the LO waveform details as has been evidenced by prior work on conversion efficiency versus LO phase noise and related studies. Of interest is how the linearity, as measured by intermodulation distortion (IMD3 for the 3rd order product), is affected by injected noise and harmonic contamination. It has been found that the effects can be profound, and with sometimes rapid onsets above certain injection levels that depend on the converter technology and harmonic order. IMD3 changes of greater than 20 dB have been observed in (broadband to) WR-6 converters as well as in WR-2.2 systems for relatively modest contamination changes.