Glossary definition of 'Intermodulation Distortion'(IMD) Intermodulation Distortion. When a signal consists of more than one frequency, a non-linear device under test will produce the original frequencies plus an infinite number of IMD products, given by
(a * F1) + (b * F2) + (c * F3) + ...
where (a, b, c) etc. are all possible integer numbers, and (F1, F2, F3) etc. are the frequencies of the original tones.