Response Coefficients of a Double-Balanced Diode Mixer

This paper presents the results of a computer-assisted analysis of a commonly used double-balanced diode mixer circuit. It is shown that the magnitudes of some of the responses to one or more input radio frequency signals are sharply dependent on the degree to which the diodes comprising the mixer are balanced. The average rejections imparted to a particular undesired intermodulation (or spurious) response by a random sample ofsuch mixers are plotted as a function ofthe tightness ofthe control of diode characteristics of the population from wl lch the four diodes comprising a single mixer are selected. A computer program based on a Fourier-series expansion of the time-dependent coefficients of a Taylor-series representation of the four diode currents was employed to compute the response coefficients of the mixer [1H3] The response coefficients are defined as the magnitudes of the intermodulations of sinusoidal-input radio-frequency signals and the local-oscillator-frequency signal. The method treats the switching action characteristic of the large local-oscillator power levels, rather than relying on the more usual and invalid [1] assumption of " mild" nonlinearity. Orders of nonlinearity up to the tenth are treated.