intermodulering

Intermodulation, often abbreviated as IM, is a phenomenon that occurs in electronic systems, particularly in radio frequency (RF) circuits, where two or more signals mix together to produce additional signals at different frequencies. This process is known as intermodulation distortion (IMD). Intermodulation can be either desired or undesired, depending on the application.

In desired intermodulation, the mixing of signals is used to generate new frequencies, which can be useful in applications such as frequency translation and signal generation. For example, in superheterodyne receivers, intermodulation is used to convert incoming signals to a fixed intermediate frequency (IF) for further processing.

Undesired intermodulation, on the other hand, is a form of distortion that can degrade the performance of electronic systems. It occurs when multiple signals are present in a circuit, and their nonlinearities cause them to mix together, producing unwanted signals at different frequencies. These unwanted signals can interfere with the desired signals, leading to poor signal quality and reduced system performance.

Intermodulation distortion is typically characterized by the intermodulation products (IMPs) that are generated. The order of an IMP is determined by the sum of the exponents of the input signals that produced it. For example, if two signals with frequencies f1 and f2 are present in a circuit, the second-order IMPs will have frequencies f1 + f2 and f1 - f2. Third-order IMPs will have frequencies 2f1 + f2, 2f1 - f2, f1 + 2f2, and f1 - 2f2, and so on.

Intermodulation can be minimized by using linear circuits and by carefully designing the system to avoid the presence of multiple signals. In some cases, intermodulation can be used to advantage, as in the case of frequency translation, but in most applications, it is considered a form of distortion that should be minimized.