Automatic frequency control (AFC)
Helgert, Hermann J. Department of Electrical and Computer Engineering, George Washington University, Washington, DC.
- Links to Primary Literature
- Additional Readings
The automatic control of the intermediate frequency in radio, television, or radar receivers, to correct for variations of the frequency of the transmitted carrier or the local oscillator in the receiver. For many reasons the frequency of the oscillators at the transmitter or receiver may fluctuate in time about its nominal value. Some of the more pronounced effects include variations in temperature or humidity, internal noise and external interference with the operation of the circuitry, and Doppler shifts of the frequency of the received signal due to movement of the transmitter or moving obstacles in a multipath channel. Automatic frequency control (AFC) is employed in radio and television receivers, FM transmitters, radar systems, satellite transceivers, and frequency synthesizers to maintain frequency stability. See also: Communications satellite; Doppler effect; Intermediate-frequency amplifier; Mobile communications; Radar; Radio receiver; Radio transmitter; Television receiver
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8700 articles covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information