GLOSSARY

Physical Units & Definitions | Satellite Terminology | Devices / Hardware | Signal Processing

 B D F G H K M S U W

 bit A unit of information representing the physical state of a system having one of two values, such as on or off. bit/s Number of bits of information transferred or transmitted every second. bps Alternative expression for bit/s. kbit/s Information transfer rate, equal to 1,000 bit/s. Mbit/s Information transfer rate, equal to 1,000,000 bit/s. byte A sequence of bits processed as one unit of information. A byte is a digital "word" normally consisting of eight bits. top

 dBi The relative gain of an antenna with respect to an equivalent isotropic antenna, expressed on the decibel logarithmic scale. dBW The power of a signal in watts, expressed on the decibel logarithmic scale. dBW/m2 Power of a radio wave incident on a surface area of one square metre, measured in watts and expressed on the decibel logarithmic scale dBK The equivalent noise temperature of a device in kelvin, expressed on the decibel logarithmic scale. dB/K 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. 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). top

 frequency 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. top

 gigahertz (GHz) Unit of frequency equal to 1,000,000,000 Hz. top

 hertz (Hz) SI unit of frequency, equivalent to one cycle per second. The frequency of a periodic phenomenon that has a periodic time of one second. top

 kelvin (K) Basic SI unit of thermodynamic temperature. kilohertz (kHz) Unit of frequency equal to 1,000 Hz. top

 megahertz (MHz) Unit of frequency equal to 1,000,000 Hz. Msymbol/s 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). top
 symbol A unique signal state of a modulation scheme used on a transmission link, which conveys one or more information bits to the receiver. symbol/s The number of symbols transmitted every second. top

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

 watt (W) SI unit of power, equal to 1 joule/second. top