Noise model for frequency translators and transposed-gain amplifiers

This paper reports phase modulation (PM) noise measurements of mixers used as frequency translators and of mixers used in homodyne systems. The relationship of the PM noise of a mixer used in a frequency translator (heterodyne system) to that in a homodyne system is not well known. The purpose of this paper is to investigate this relationship (if any). We found that the PM noise of mixers used in heterodyne systems consists of a 1/f portion decreasing to a thermal noise floor characterized by the temperature and conversion loss. The 1/f PM noise is typically 4-7 dB lower than in a heterodyne system for the same mixer used.