RF Limiter Basics: Application and Manufacturers

This page covers RF Limiter basics and includes an application note, as well as a list of RF power Limiter manufacturers. Typically, a Limiter is any device that limits the input signal above a certain threshold set by the manufacturer.

For example, a conventional class-A amplifier can act as a limiter if the input signal is very high in magnitude. With a very large input signal applied to the transistor, it will drive the transistor between saturation and cutoff.

An RF Limiter is specifically designed to limit signals within the radio frequency (RF) spectrum range. As mentioned, a limiter operates in saturated mode, so its output spectrum contains harmonics of the applied input signal. The harmonic content depends on the applied power level as well as the bias current. RF Limiters are mainly designed and developed using diodes such as PIN diodes and Schottky diodes.

RF Limiter Application

In an FM receiver, one or more IF amplifiers are used as limiters. As mentioned, limiters remove any undesired amplitude variations from the received FM signal. This signal is then fed to the FM demodulator portion. This is depicted in the figure above.

Mini-Circuits provides RF limiters in a wide range of frequencies from 3 KHz to 900 MHz with a dynamic range between 3 to 20 dBm. These RF limiters produce a 0.05 dB output change for a 1 dB input change. A key benefit is that they introduce very little phase variation to the input signal during the limiting operation.

Dynamic Range Considerations

As we know, dynamic range is the range from minimum to maximum amplitude over which a limiter is useful within an electronic circuit. What happens if the RF signal level provided as input is outside the dynamic range of the limiter? There are two possible scenarios:

• If the input level is very high, an attenuator should be used.
• If the input level is very low, an amplifier should be used.

Both components are used so that the RF input signal level remains within the designed dynamic range of the RF limiter.

RF Power Limiter Manufacturers

The following specifications are considered when selecting the right RF power limiter:

• Frequency range of operation
• Input power (Maximum)
• Input peak power (Maximum)
• Insertion loss: The loss to the signal as it travels from input to the output.
• Package type: Connectorized or in the form of a drop-in module.

The following table lists RF limiter manufacturers: