The power of an AM signal plotted against frequency.
Key: fc is the carrier frequency, fm is the maximum modulation frequency

In radio communications, a sideband is a band of frequencies higher than or lower than the carrier frequency, containing power as a result of the modulation process. Radio is the transmission of signals by Modulation of electromagnetic waves with frequencies below those of visible Light. A band is a small section of the spectrum of Radio communication frequencies, in which channels are usually used or set aside for the same Frequency is a measure of the number of occurrences of a repeating event per unit Time. In Telecommunications, modulation is the process of varying a periodic Waveform, i The sidebands consist of all the Fourier components of the modulated signal except the carrier. All forms of modulation produce sidebands.

Amplitude modulation of a carrier wave normally results in two mirror-image sidebands. In Telecommunications, a carrier wave, or carrier is a Waveform (usually Sinusoidal) that is modulated (modified with an input signal The signal components above the carrier frequency constitute the upper sideband (USB) and those below the carrier frequency constitute the lower sideband (LSB). In conventional AM transmission, the carrier and both sidebands are present, sometimes called double sideband amplitude modulation (DSB-AM). In Telecommunications transmission is the process of sending propagating and receiving an analogue or digital information signal over a physical point-to-point or

In some forms of AM the carrier may be removed, producing double sideband with suppressed carrier (DSB-SC). An example is the stereophonic difference (L-R) information transmitted in FM stereo broadcasting on a 38 kHz subcarrier. Stereophonic sound, commonly called stereo, is the reproduction of Sound, using two or more independent audio channels through a Symmetrical A subcarrier is a separate analog or Digital signal carried on a main radio transmission, which carries extra information such as Voice The receiver locally regenerates the subcarrier by doubling a special 19 kHz pilot tone, but in other DSB-SC systems the carrier may be regenerated directly from the sidebands by a Costas loop or squaring loop. In Telecommunications a pilot is a signal, usually a single Frequency, transmitted over a Communications system for supervisory control In Telecommunication, a Costas loop is a Phase-locked loop used for carrier phase recovery from suppressed-carrier Modulation signals This is common in digital transmission systems such as BPSK where the signal is continually present. Phase-shift keying (PSK is a Digital Modulation scheme that conveys data by changing or modulating the phase of a reference signal

Sidebands are evident in this Fourier transform of an AM broadcast (carrier highlighted in red).

If part of one sideband and all of the other remain, it is called vestigial sideband, used mostly with television broadcasting, which would otherwise take up an unacceptable amount of bandwidth. Television ( TV) is a widely used Telecommunication medium for sending ( Broadcasting) and receiving moving Images, either monochromatic For the band see Broadcast (band Broadcasting is the distribution of audio and/or Video signals which transmit Transmission in which only one sideband is transmitted is called single-sideband transmission or SSB. Single-sideband modulation ( SSB) is a refinement of Amplitude modulation that more efficiently uses electrical power and bandwidth. SSB is the predominant voice mode on HF radio. Since the sidebands are mirror images, which sideband is used is a matter of convention. In amateur radio, LSB is traditionally used below 10 MHz and USB is used above 10 MHz. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications

In SSB, the carrier is suppressed, significantly reducing the electrical power (by up to 12 dB) without affecting the information in the sideband. Reduced-carrier transmission is an Amplitude modulation (AM transmission in which the Carrier wave level is reduced to reduce Wasted electrical Electric power is defined as the rate at which Electrical energy is transferred by an Electric circuit. This makes for more efficient use of transmitter power and RF bandwidth, but a beat frequency oscillator must be used at the receiver to reconstitute the carrier. A beat frequency oscillator or BFO in Radio telegraphy, is a dedicated Oscillator used to create an audio frequency signal from Carrier wave This article is about a radio receiver for other uses see Radio (disambiguation. In Telecommunications, a carrier wave, or carrier is a Waveform (usually Sinusoidal) that is modulated (modified with an input signal Another way to look at an SSB receiver is as an RF-to-audio frequency translator: in USB mode, the dial frequency is subtracted from each radio frequency component to produce a corresponding audio component, while in LSB mode each incoming radio frequency component is subtracted from the dial frequency.

Sidebands can also interfere with adjacent channels. In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern In broadcasting an adjacent channel is an AM, FM, or TV channel that is next to another channel. The part of the sideband that would overlap the neighboring channel must be suppressed by filters, before or after modulation (often both). Electronic filters are Electronic circuits which perform Signal processing functions specifically intended to remove unwanted signal components and/or enhance wanted In Broadcast band frequency modulation (FM), subcarriers above 75 kHz are limited to a small percentage of modulation and are prohibited above 99 kHz altogether to protect the ±75 kHz normal deviation and ±100 kHz channel boundaries. Broadcast band commonly refers to several segments of the Radio spectrum. A subcarrier is a separate analog or Digital signal carried on a main radio transmission, which carries extra information such as Voice The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. In Mathematics, a percentage is a way of expressing a number as a Fraction of 100 ( per cent meaning "per hundred" Channel, in communications (sometimes called communications channel) refers to the medium used to convey Information from a Amateur radio and public service FM transmitters generally utilize ±5 kHz deviation. Amateur radio, often called ham radio, is both a Hobby and a service in which participants called "hams" use various types of Radio communications

See also

• Single-sideband modulation for more technical information about sideband modulation

References

• partly from Federal Standard 1037C in support of MIL-STD-188
• partly from Department of The Army Technical Manual TM 11-685 "Fundamentals of Single Sideband Communications"