# Bandwidth (signal processing)

bandwidthbandwidthssignal bandwidthspectral bandwidthfractional bandwidthhigh-bandwidthradio bandwidthEssential bandwidthPassband bandwidthanalog bandwidth
Bandwidth is the difference between the upper and lower frequencies in a continuous band of frequencies.wikipedia
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### Communication channel

channelchannelscommunications channel
Passband bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a band-pass filter, a communication channel, or a signal spectrum.
A channel has a certain capacity for transmitting information, often measured by its bandwidth in Hz or its data rate in bits per second.

### Band-pass filter

bandpass filterbandpassband-pass
Passband bandwidth is the difference between the upper and lower cutoff frequencies of, for example, a band-pass filter, a communication channel, or a signal spectrum.
The bandwidth of the filter is simply the difference between the upper and lower cutoff frequencies.

tunerTV tunertuners
A tuner is a subsystem that receives radio frequency (RF) transmissions like radio broadcasts and converts the selected carrier frequency and its associated bandwidth into a fixed frequency that is suitable for further processing, usually because a lower frequency is used on the output.

Because transmitted FM signals use more bandwidth than AM signals, this form of modulation is commonly used with the higher (VHF or UHF) frequencies used by TV, the FM broadcast band, and land mobile radio systems.

Bandwidth in hertz is a central concept in many fields, including electronics, information theory, digital communications, radio communications, signal processing, and spectroscopy and is one of the determinants of the capacity of a given communication channel.
The width in hertz of the frequency range that the radio signal occupies, the highest frequency minus the lowest frequency, is called its bandwidth (BW).

### Nyquist–Shannon sampling theorem

sampling theoremNyquist-Shannon sampling theoremNyquist theorem
In the context of, for example, the sampling theorem and Nyquist sampling rate, bandwidth typically refers to baseband bandwidth.
It establishes a sufficient condition for a sample rate that permits a discrete sequence of samples to capture all the information from a continuous-time signal of finite bandwidth.

### Telecommunication

telecommunicationscommunicationstelecom
Bandwidth is a key concept in many telecommunications applications.
According Edholm's law, the bandwidth of telecommunication networks has been doubling every 18 months.

### Frequency response

frequency response functionfrequencyresponse function
In the case of frequency response, degradation could, for example, mean more than 3 dB below the maximum value or it could mean below a certain absolute value.
That would require a uniform (flat) magnitude of response up to the bandwidth limitation of the system, with the signal delayed by precisely the same amount of time at all frequencies.

### Hertz

MHzkHzHz
It is typically measured in hertz, and depending on context, may specifically refer to passband bandwidth or baseband bandwidth.

### Baseband

baseband signalbase bandcellular baseband
In the context of, for example, the sampling theorem and Nyquist sampling rate, bandwidth typically refers to baseband bandwidth. Baseband bandwidth applies to a low-pass filter or baseband signal; the bandwidth is equal to its upper cutoff frequency.
A baseband bandwidth is equal to the highest frequency of a signal or system, or an upper bound on such frequencies, for example the upper cut-off frequency of a low-pass filter.

### Shannon–Hartley theorem

Shannon-Hartley theoremHartley's lawShannon limit
In the context of Nyquist symbol rate or Shannon-Hartley channel capacity for communication systems it refers to passband bandwidth.
In information theory, the Shannon–Hartley theorem tells the maximum rate at which information can be transmitted over a communications channel of a specified bandwidth in the presence of noise.

### Plain old telephone service

POTSLocal Telephone Servicetelephone
For example, a 3 kHz band can carry a telephone conversation whether that band is at baseband (as in a POTS telephone line) or modulated to some higher frequency.
Although POTS provides limited features, low bandwidth, and no mobile capabilities, it provides greater reliability than other telephony systems (mobile phone, VoIP, etc.).

### Nyquist rate

Nyquist sampling rateNyquist limitNyquist
In the context of, for example, the sampling theorem and Nyquist sampling rate, bandwidth typically refers to baseband bandwidth. In the context of Nyquist symbol rate or Shannon-Hartley channel capacity for communication systems it refers to passband bandwidth.
In terms of a function's own bandwidth (B), as depicted above, the Nyquist criterion is often stated as f s > 2B.

### Channel capacity

capacitydata capacityinformation capacity
In the context of Nyquist symbol rate or Shannon-Hartley channel capacity for communication systems it refers to passband bandwidth.
An application of the channel capacity concept to an additive white Gaussian noise (AWGN) channel with B Hz bandwidth and signal-to-noise ratio S/N is the Shannon–Hartley theorem:

### Passband

pass bandpass-bandpassband signal
In the context of Nyquist symbol rate or Shannon-Hartley channel capacity for communication systems it refers to passband bandwidth.
Radio receivers generally include a tunable band-pass filter with a passband that is wide enough to accommodate the bandwidth of the radio signal transmitted by a single station.

### Wideband

In the field of antennas, two different methods of expressing relative bandwidth are used for narrowband and wideband antennas.
In communications, a system is wideband when the message bandwidth significantly exceeds the coherence bandwidth of the channel.

### Narrowband

narrow-bandnarrownarrow band
In the field of antennas, two different methods of expressing relative bandwidth are used for narrowband and wideband antennas.
In radio communications, a narrowband channel is a channel in which the bandwidth of the message does not significantly exceed the channel's coherence bandwidth.

### Full width at half maximum

FWHMhalf-widthbeamwidth
This same half-power gain convention is also used in spectral width, and more generally for extent of functions as full width at half maximum (FWHM).
The convention of "width" meaning "half maximum" is also widely used in signal processing to define bandwidth as "width of frequency range where less than half the signal's power is attenuated", i.e., the power is at least half the maximum.

A government agency (such as the Federal Communications Commission in the United States) may apportion the regionally available bandwidth to broadcast license holders so that their signals do not mutually interfere.

### Bandwidth (computing)

bandwidthnetwork bandwidthInternet bandwidth
This definition of bandwidth is in contrast to the field of signal processing, wireless communications, modem data transmission, digital communications, and electronics, in which bandwidth is used to refer to analog signal bandwidth measured in hertz, meaning the frequency range between lowest and highest attainable frequency while meeting a well-defined impairment level in signal power.

### Control theory

controlcontrollercontrol theorist
In signal processing and control theory the bandwidth is the frequency at which the closed-loop system gain drops 3 dB below peak.

### Spectral efficiency

system spectral efficiencylink spectral efficiencySpectral efficiency comparison table
Spectral efficiency, spectrum efficiency or bandwidth efficiency refers to the information rate that can be transmitted over a given bandwidth in a specific communication system.

### Frequency domain

frequency-domainFourier spaceFourier domain
In basic electric circuit theory, when studying band-pass and band-reject filters, the bandwidth represents the distance between the two points in the frequency domain where the signal is of the maximum signal amplitude (half power).
In addition, looking at a system from the point of view of frequency can often give an intuitive understanding of the qualitative behavior of the system, and a revealing scientific nomenclature has grown up to describe it, characterizing the behavior of physical systems to time varying inputs using terms such as bandwidth, frequency response, gain, phase shift, resonant frequencies, time constant, resonance width, damping factor, Q factor, harmonics, spectrum, power spectral density, eigenvalues, poles, and zeros.

### Bandwidth

Bandwidth (disambiguation)