Testing Lab Series

IMD Pan Test

IMD or Intermodulation Distortion occurs when two or more transmitted frequencies become non-linear. It is not necessary to understand this concept at this time. It is more important to understand when IMDs occur and how to prevent them from occurring or avoid them. Lets look at some practical examples of when IMDs occur.

One very common causes of IMD occurs when you have two of more microphones very close to each other. This commonly happens when you set out microphones on a table, or the top of a rack ready to be used. We are going to do some testing to determine the impact of this process on the generation of IMDs.

Observations: 2tone3rd IMD average is greater than half the average dBm of primary tones. 2tone5ths IMD are greater than 10dBm above the noise floor.


Note: These results were not as expected and the IMDs are of higher power than in test #1. This method is often seen in practice and it is commonly assumed that this method would reduce the generation of IMDs testing does not support this.