Sinusoidal inputs applied to a nonlinear system produce an output containing different frequencies, and the results can be good, bad, or ugly.
According to the dictionary definition, intermodulation is “the production in an electrical device of currents having frequencies equal to the sums and differences of frequencies supplied to the device.” In the literature of electrical engineering, the word is often followed by the word distortion. Indeed, intermodulation distortion (IMD) is bad — a problem to eliminate. However, the process that causes IMD is often put to good use in communications and test applications.
What’s an example of a good use?
Frequency translation — upconversion or downconversion. Upconversion translates a baseband or intermediate-frequency (IF) signal into an RF signal for transmission; it finds use in arbitrary waveform generators. Downconversion…
