How to model intermodulation distortion

The author examines the problem of calculating intermodulation levels and mixer spurious responses in nonlinear microwave circuits. It is shown that, in order to perform such calculations successfully, the expression for the I/V characteristic of the solid-state device must accurately reproduce not only the characteristic itself, but also its derivatives. One must furthermore choose the most appropriate analytical technique and be mindful of the dynamic-range limitations of Fourier transforms, of the need to use an adequate and correct set of frequency components, and finally of the limitations of linear-element models. Ways to obtain accurate analyses of these phenomena using available harmonic-balance and Volterra-series circuit simulators are described.<>