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What Is a Carrier Recovery?

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  • Written By: Mary McMahon
  • Edited By: Shereen Skola
  • Last Modified Date: 15 July 2014
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    Conjecture Corporation
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Carrier recovery allows the receiver of a communications system to demodulate an incoming waveform in order to extract meaningful information. Both frequency and phase may be altered in transmission on a carrier wave, making recovery necessary for the receiver unit to convey the information to a user or another system. This is done with the assistance of a specialized circuit inside the receiver, programmed for this function. Errors in carrier recovery can result in problems with incoming data. When data becomes garbled, a technician may check on various components of the system to track down the source of the problem and implement an appropriate repair.

In transmissions, a transmitting unit will modulate the wave before sending it out. Receivers are not necessarily synchronized to transmitters, and must be able to demodulate the wave to extract the information. Sometimes receiver units are newer or older or have different settings. Even if two units are theoretically synchronized, factors like temperature and distance can distort the wave and make it unreadable when it arrives.

The carrier recovery circuit evaluates the incoming wave and determines which frequency and phase shifts were applied so it can grab the necessary information. This requires taking a selective sampling to compensate for minor errors and shifts. If the carrier recovery was based on just one sample, an error might occur, but an assortment allows it to average and discard unusually high and low values that are clearly mistakes.

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A variety of communications circuits rely on this technology to convey information back and forth between locations. These can include base stations as well as relay transmitters for various types of communications systems like phones, radios, and Internet networks. Complex networks may include an array of receivers, transmitters, and dual purpose units, each of which needs to perform its own carrier recovery to access the information embedded in the carrier wave.

It is also possible to encrypt the information for added security. In this case, the carrier recovery will provide a clean version of the encrypted data, which must be run through a decryption algorithm to get the information. This ensures that organizations can transfer sensitive information with reasonable security, as long as the encryption algorithm is only known to limited numbers of people. There are a variety of technologies available for encryption of information before transmission in a carrier wave, and the best may depend on the setting and the type of information.

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