What is a Limiting Amplifier?

In many microwave circuits, especially receiver circuits, there is a limit to the amount of signal power that the circuit can handle before causing undesirable operation, damage, or destruction of the circuit. With high sensitivity receiver circuits for applications such as electronic warfare (EW), signal intelligence (SIGINT), radar, interference limited wireless communication, and others, signal levels beyond an acceptable threshold could desensitize the receiver or destroy it. Hence, the use of limiting amplifiers that leverage additional circuitry to cap the maximum signal power over a frequency range, regardless of the input signal strength.

There are a variety of different types of limiting amplifiers, some that simply shunt extra signal power away from the sensitive circuitry, and others that use successive gain compression stages to deliver a signal output power which remains relatively constant. Like many microwave amplifiers, linearity, dynamic range, noise, phase noise, gain, bandwidth, and gain flatness are critical parameters to consider when designing or selecting a limiting amplifier.

Other considerations include application specific requirements, such as temperature stability, high reliability, high maximum input signal power, low harmonics over a multi-octave frequency range, and environmental ruggedness. As many of the use cases for limiting amplifiers are in military, defense, government, or other critical communications and sensing, limiting amplifiers are often assembled in rugged and hermetically sealed enclosures with connectorized input and output ports.