A unit of information representing the physical state of a system having one of two values, such as on or off.


Number of bits of information transferred or transmitted every second.


Alternative expression for bit/s.


A sequence of bits processed as one unit of information. A byte is a digital "word" normally consisting of eight bits.


Units used to express the Figure of Merit or G/T of an earth station, with the dimensions of 1/kelvin, expressed on the decibel logarithmic scale.


The relative gain of an antenna with respect to an equivalent isotropic antenna, expressed on the decibel logarithmic scale.


The equivalent noise temperature of a device in kelvin, expressed on the decibel logarithmic scale.


The power of a signal in watts, expressed on the decibel logarithmic scale.


Power of a radio wave incident on a surface area of one square metre, measured in watts and expressed on the decibel logarithmic scale

decibel (dB)

A unit for comparing two currents, voltages or power levels based on a logarithmic scale. It is used particularly for expressing the difference between very large and very small values (expression: R = 10*log10(r), where r is the linear ratio and R is the ratio in dB).


The number of times that an electrical or electromagnetic signal repeats itself in a specified time. It is usually expressed in cycles per second, or hertz (Hz). Satellite transmission frequencies are usually expressed in gigahertz (GHz).

Frequency band

A range of frequencies used for transmission or reception of radio waves (e.g. 10.7 GHz to 12.75 GHz).

Frequency spectrum

A particular distribution of electromagnetic radiation with frequency, which is characteristic of the source of the emission. In satellite communication systems, the spectrum of a transmitted signal depends upon the modulation scheme employed. The term "frequency spectrum" is also used more generally to refer to a continuous range of frequencies.

gigahertz (GHz)

Unit of frequency equal to 1,000,000,000 Hz.


High Definition TV has a screen ratio of 16:9, and is normally provided with 5.1 independent channels of CD-quality stereo surround sound (also referred to as AC-3).

The video signal enables an increased image resolution by offering up to 1080 active lines and 1920 pixels per line, instead of the 576 lines and 720 pixels per line provided by the PAL TV standard. The increased resolution at progressive scan instead of interlaced makes the picture extremely sharp.

Hertz (Hz)

The SI unit of frequency, equivalent to one cycle per second. The frequency of a periodic phenomenon that has a periodic time of one second.


Information transfer rate, equal to 1,000 bit/s.

kelvin (K)

Basic SI unit of thermodynamic temperature.

kilohertz (kHz)

Unit of frequency equal to 1,000 Hz.


Information transfer rate, equal to 1,000,000 bit/s.

megahertz (MHz)

Unit of frequency equal to 1,000,000 Hz.


Unit of data transmission rate for a radio link, equal to 1,000,000 symbol/s. Can be directly related to the bandwidth required to establish the transmission link (e.g. 33 MHz for a transmission rate of 27.5 Msymbol/s).


A unique signal state of a modulation scheme used on a transmission link, which conveys one or more information bits to the receiver.


The number of symbols transmitted every second.


Coordinated Universal Time. A time-scale which forms the basis of a coordinated dissemination of standard frequencies and time signals throughout the world.

Watt (W)

SI unit of power, equal to 1 joule/second.