RF Comb Generator for EMC and RFI Testing

This page covers RF Comb Generator basics and describes how to use a comb generator for EMC (Electromagnetic Compatibility) testing or RFI (Radio Frequency Interference) testing. It also lists manufacturers of low phase noise RF comb generators.

A comb generator is a signal generator that produces harmonics of its input signal. The output spectral components are spaced at equal intervals. For example, if the input is $F_{in}$, it will produce $\pm K \cdot F_{in}$, where $K$ ranges from 1, 2, 3, and so on. The frequency spectrum, when viewed on an analyzer, resembles the teeth of a comb, hence the name “comb generator.”

Figure-1 depicts function of comb generator.

As we know, EMI refers to Electromagnetic Interference, and EMC refers to Electromagnetic Compatibility.

Comb generators are used for both EMI and EMC testing. Another widespread application of comb generators is in broadband frequency synthesizers. These synthesizers generate high-frequency outputs referenced to a low-frequency source. This highly stable, high-frequency output is then used as a frequency reference input in a PLL (Phase-Locked Loop) circuit.

Using Comb Generator for EMC Testing or RFI Testing

Figure-2 depicts radiated emission test (EMI) using comb generator.

Figure-3 depicts conducted emission test (EMC) using comb generator.

It is very easy to use a comb generator. Simply connect the port to the antenna, and it will start radiating. The Low Phase Noise Model No-7112 from Picosecond Pulse Labs is a high-performance comb generator. The comb generator operates over a specified input frequency and power range.

The following are the specifications of the comb generator:

Manufacturers of Low Phase Noise RF Comb Generators

The following are popular vendors or manufacturers of low phase noise RF comb generators: