7E Communications
   

Glossary Terms Beginning C

0-9 : A : B : C : D : E : F : G : H : I : J : K : L : M

N : O : P : Q : R : S : T : U : V : W : X : Y : Z

C/N
See Carrier-to-noise ratio.
Capacity
Satellite bandwidth or channel.
Carrier; carrier frequency
Continuous (usually high-frequency) electromagnetic wave which can be modulated by a baseband signal to carry information; main frequency on which a voice, data or video signal is sent.
Carrier-to-noise ratio
C/N: the ratio of the received carrier power and the noise power in a given bandwidth, expressed in dB. Cascading Concatenating connection of devices.
C-band
Frequencies in the 4-6 GHz range, used both for terrestrial microwave links and satellite links.
CCIR-601
Recommendation developed by the CCIR for the digitization of colour video signals; now ITU-R BT.601
CDMA
Code division multiple access: refers to a multiple-access scheme where the transmission process uses spread-spectrum modulations and orthogonal codes to avoid the signals interfering with one another.
Centre frequency
Frequency of the centre of a channel on a satellite transponder.
CEPT
Conference Europeane des Administrations des Postes et des Telecommunications.
CES
Coast earth station: alternative term for LES in INMARSAT system.
CFR
Code of Federal Regulations (US).
Chain
Transmission path; usually in an SNG uplink referring to the equipment that makes up the transmission channel.
Channel
Specific frequency range in which a signal is transmitted in a satellite transponder.
Check-bits
Data bits added for error detection.
Chip-set
Set of integrated circuit devices which form the heart of a compression encoder.
Chrominance
Colour signal.
CIF
Common intermediate format: developed so that computerized video images could be shared from one computer to another. An image that is digitized to CIF format has a resolution of 352 288 or 352 240, which is essentially one-half of CCIR-601.
Circular polarization
Geometric plane in which the electromagnetic signals are transmitted. Circular polarization can be either clockwise (left-hand circular polarization, or LHCP) or counter-clockwise (right-hand circular polarization, or RHCP).
Clamp
Video processing circuit that removes the energy dispersal signal component from the video waveform.
Clarke Belt; Clarke Orbit
Geostationary orbit; named in honour of Arthur C. Clarke.
Clean carrier
Unmodulated carrier signal.
Cleanfeed
Studio audio output transmitted to the remote site so that the reporter is able to conduct a two-way dialogue with the studio presenter. Also called IFB, mix-minus, return sound or return audio.
Cliff-edge effect
Describes the fact that digital signals suffer from achieving either perfect results or nothing: as a digital signal passes a particular threshold, the signal fails catastrophically with no warning.
Coax
Coaxial cable, used for carrying signals at frequencies from video baseband up to IF.
Codec
COder/DECoder: a device which converts an analogue signal into or from a digital signal.
Coding delay
See Latency.
Coding order
Order in which a group of pictures is coded in a digital compression process.
Coefficient
Mathematical term for a number with a particular algebraic significance.
Co-located
Where a number of satellites share the same geostationary orbital assignment.
Common carrier
Regulated telecommunications company which will carry signals for a fee; common carriers include telephone companies as well as owners of communications satellites.
Companding
COMpressing/exPANDING: a noise-reduction technique that applies compression at the transmitter and complementary expansion at the receiver.
Compression
Process of removing redundant data to minimize the use of bandwidth, ideally without visibly or audibly degrading the programme.
Convolutional code
Type of error correction code used in digital coding.
Cross-modulation
Form of signal distortion in which modulation from one or more RF carrier(s) is imposed on another carrier.
Cross-polar discrimination
XPD: measurement of immunity from interference from signals on the opposite polarization; describes the ratio of (wanted) signals on the desired polarization compared to the (unwanted) signals on the opposite polarization.
Cross-polar interference
XPI: interference from signals in the same transponder (IPs) or adjacent transponders, and signals at similar frequencies but on the opposite polarization - related to XPD
Cross-strapping
Process on-board a satellite where an uplinked signal in one frequency band is converted to a different frequency band for the downlink, e.g. C-band uplink to Ku-band downlink.
Cross-talk
Unwanted leakage of signal from one channel to another.