Two-Tone Intermodulation in Diode Mixers

摘要

This report explores, experimentally and theoretically, the problem of minimizing second- and third-order intermodulation distortion in diode mixers. A numerical technique is presented which can be used to calculate intermodulation levels with unprecedented accuracy, and it is used to identify circuit and diode parameters which maximize dynamic range. It is shown that intermodulation distortion is minimized by using low diode junction capacitance and series resistance, short-circuit embedding impedances, and high local oscillator level. It is also shown that certain conditions which may optimize conversion loss, such as image enhancement, may severely exacerbate intermodulation. The theory is applicable at RF levels below saturation.