ギルバートミキサ回路におけるスイッチから発生する雑音の解析

摘要

A noise analysis of Gilbert mixer using Bipolar Junction Transistors (BJT) for usewith direct conversion receiver mixers is presented. Noises are treated as amplitude modulated white noises, which are characterized as cyclostationary noises, and all the folding effects are taken into account. This analysts considers thermal noise from base resistance and shot noise from collector current. First, output noise power spectrum densities are calculated for static local oscillator (LO) drive for collector shot noises and base resistance thermal noises. Next, we calculate the output power spectrum densities for sinusoidaJ and rectangular wave LO drive. We found that rectangular wave case produces much less noise for LO drive amplitude of larger than 0.1[V]. Finally, effects of parastic capacitances on the output noise are analyzed, and we found that the effects are almost negligible up to a few GHz for 10[GHz] fr device with typical operation conditions. These results theoretically support the insights which have been known to experienced circuit designers.