Radio frequency sweep or frequency sweep or RF sweep apply to scanning a radio frequency band for detecting signals being transmitted there. This is implemented using a radio receiver having a tunable receiving frequency. As the frequency of the receiver is changed to scan (sweep) a desired frequency band, a display indicates the power of the signals received at each frequency.
Methods and tools
A
spectrum analyzer is a standard instrument used for RF sweep. It includes an electronically tunable receiver and a display. The display presents measured power (y axis) vs frequency (x axis).
The power spectrum display is a two-dimensional display of measured power vs. frequency. The power may be either in linear units, or logarithmic units (dBm). Usually the logarithmic display is more useful, because it presents a larger dynamic range with better detail at each value. An RF sweep relates to a receiver which changes its frequency of operation continuously from a minimum frequency to a maximum (or from maximum to minimum). Usually the sweep is performed at a fixed, controllable rate, for example 5 MHz/sec.
Some systems use
frequency hopping, switching from one frequency of operation to another. One method of
CDMA uses frequency hopping. Usually frequency hopping is performed in a random or pseudo-random pattern.
Applications
Frequency sweeps may be used by regulatory agencies to monitor the
radio spectrum
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 0 Hz to 3,000 GHz (3 THz). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particula ...
, to ensure that users only transmit according to their licenses. The FCC for example controls and monitors the use of the spectrum in the U.S. In testing of new electronic devices, a frequency sweep may be done to measure the performance of electronic components or systems. For example, RF oscillators are measured for phase noise, harmonics and spurious signals; computers for consumer sale are
tested to avoid
radio frequency interference with radio systems. Portable sweep equipment may be used to detect some types of
covert listening device
A covert listening device, more commonly known as a bug or a wire, is usually a combination of a miniature radio transmitter with a microphone. The use of bugs, called bugging, or wiretapping is a common technique in surveillance, espionage and ...
(bugs).
In
professional audio, the optimum use of
wireless microphone
A wireless microphone, or cordless microphone, is a microphone without a physical cable connecting it directly to the sound recording or amplifying equipment with which it is associated. Also known as a radio microphone, it has a small, battery- ...
s and
wireless intercoms may require performing a sweep of the local radio spectrum, especially if many wireless devices are being used simultaneously. The sweep is generally limited in bandwidth to only the operating bandwidth of the wireless devices. For instance, at American
Super Bowl
The Super Bowl is the annual final playoff game of the National Football League (NFL) to determine the league champion. It has served as the final game of every NFL season since 1966, replacing the NFL Championship Game. Since 2022, the game ...
games, audio engineers monitor (sweep) the radio spectrum in real time to make certain that all local wireless microphones are operating at previously agreed-upon and coordinated frequencies.
[ Local Coordination: Event-specific coordination.]
See also
*
Measuring receiver
In telecommunication, a measuring receiver or measurement receiver is a calibrated laboratory-grade radio receiver designed to measure the characteristics of radio signals. The parameters of such receivers (tuning frequency, receiving bandwidth, ...
*
Spectrum management
Spectrum management is the process of regulating the use of radio frequencies to promote efficient use and gain a net social benefit.Martin Cave, Chris Doyle, William Webb, ''Modern Spectrum Management'', Cambridge University Press, 2007 The term ...
*
Technical surveillance counter-measures
Countersurveillance refers to measures that are usually undertaken by the public to prevent surveillance, including covert surveillance. Countersurveillance may include electronic methods such as technical surveillance counter-measures, which is ...
References
*Donald G. Fink, Donald Christiansen – Electronic Engineer's Handbook, Second edition.
*Ulrich L. Rohde, Jerry C. Whitaker, T.T.N. Bucher – Communications Receivers: Principles and Design, Second edition.
{{DEFAULTSORT:Radio frequency sweep
Electronic test equipment
Laboratory equipment
Measuring instruments
Radio technology
Signal processing
Covert listening devices