RF Amplifiers & Microwave Amplifiers

Common Questions About RF Amplifiers and Microwave Amplifiers

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How are RF amplifiers used?

RF amplifiers are used for many purposes within the communication process, including:

  • Power amplifier: RF amplifiers can function as power amplifiers when they give gain to the signal before transmission and is connected to the transmitting antenna.
  • Low noise amplifier: RF amplifiers, when connected just after a signal is received, is considered a low noise amplifier (LNA). As an LNA, it amplifies distorted signals received without also amplifying any accompanying noise.
  • Gain amplifier: When used as a variable gain amplifier on a rapidly changing mobile channel, they help recover the transmitted information within the receiver.
What are some of the terms used with RF amplifiers?

To use, test, and design with RF amplifiers, knowing some of the terminology can be helpful. Some of the more common terms are as follows:

  • Power: Ordinarily used as a measurement unit for intermediate frequency (IF) and RF signals, this is expressed in decibel-milliwatts (dBm) or decibel watts (dBW).
  • Gain: Gain is the ratio of output power of the amplifiers device to the input power, expressed in decibels (dB).
  • VSWR: VSWR means voltage standing wave ratio, a measurement unit of the accuracy of impedance matching at a connection point. Usually used at microwave frequencies, its expressed as a ratio like 1.3:1. Its most commonly used at IF frequencies as return loss.
  • Return loss: Similar function to VSWR but expressed instead in dB.
  • Insertion loss: Insertion loss is a ratio of the output power of an attenuating device to the input power, expressed in dB.
  • Harmonics: Harmonics are frequencies at integer multiples of input frequencies produced by all frequency converters and signal sources.
  • Spurious: All signal source and frequency converters output frequencies at non-integer multiples of input frequencies, and theyre called spurious.
What is an RF, or microwave, amplifier?

A radio frequency (RF) power amplifier is an electric amplifier that takes low-power radio signals and converts them into a higher power signal so it can go farther. They work with a transmitters antenna to accomplish this. The power output, gain, bandwidth, power efficiency, linearity (low signal compression), heat dissipation, input, and output round out the elements of the design. Many newer RF amplifiers have different mods of operation, classes, to help obtain different broadcast goals.