Antenna Control Unit
The horizontal angle a parabolic antenna must be rotated to, in order to point to a specific satellite in the orbit. It is defined with respect due to north for an easier convenience.
Band Pass Filter
A circuit which allows only those signals within the desired frequency band to pass through.
The width of the available frequency spectrum or capacity.
The angle of the beam of the antenna for which the signal strength decreases no more than 3dB (half signal strength) in ratio to the maximum signal strength.
A Block Up Converter is used in the transmission (uplink) of satellite signals. It converts a band of frequencies from a lower frequency to a higher one. Modern BUCs convert from L band to Ku band, C band and Ka band.
The main frequency on which a voice, data or video signal is sent.
Carrier to Noise Ratio (C/N)
The ratio of the received modulated carrier signal power (C) to the received noise power (N) in a given bandwidth, expressed in dB. The higher the C/N the better the signal quality.
An antenna priciple that uses a subreflector at the focal point, which reflects the signal to or from a feed located at the apex of the main reflector.
A continuous wave or continuous waveform (CW) is an electromagnetic wave of constant amplitude and frequency; and in mathematical analysis, of infinite duration.
The decibel is a logarithmic unit of measurement that expresses the ratio between two power levels.
The dB power relative to an isotropic source.
The ratio of the power to one Watt expressed in decibel.
The path of a 2 way satellite communication from the satellite to earth.
Equivalent Isotropic Radiated Power - describes the strength of the signal leaving the satellite antenna (product of the transponder output power and the gain of the satellite transmit antenna in dBW) and is used for determining the C/N and S/N.
Eastern Limit Switch.
Ratio of antenna focal length to antenna diameter.
The feed system of an antenna, which may consist of a subreflector plus a feed-horn or a feed-horn only.
A satellite antenna component that collects the signal reflected from the main reflector (primary focused antenna) or the subreflector (cassegrain antenna) and channels this signal into the Low-Noise-Amplifier (LNA).
Frequency Shift Keying Transmitter.
The amplification of an antenna expressed in dB.
The main station through which all communications to, from and between micro terminals must flow.
The INternational MARitime SATellites operates as a network for international transmissions for all type of international mobile services. Together, these satellites cover the most of the earth.
The Ka-Band covers the frequencies of 29.5-30 GHz, i.e. wavelengths from slightly over one centimeter down to 0.75 centimeters. The Ka-Band is part of the K-Band of the microwave band of the electromagnetic spectrum.
The frequency range from 10.7 to 18 GHz.
Lower Limit Switch.
Low Noise Block Converter.
Low Noise Amplifier (LNA)
The preamplifier between the antenna and the earth-station receiver which contributes the least amount of thermal noise to the received signal.
Low Noise Block / Converter (LNB / LNC)
A combination of a Low Noise Amplifier and a down-converter built into one device attached to the feed.
Is the difference between the level of the satellite system and the minimum levels required for operation.
An antenna whose shape is mathematically described as a parabola. The shape focuses the weak microwave signal into a focal point in the front of the dish where the feed-horn or a second reflector (subreflector) is located.
Phase Locked Loop.
An electronic device which separates a particular satellite signal from all other received signals and converts it into a format for video, voice or data.
Off-axis response of an antenna.
Signal to Noise Ratio (S/N)
The ratio of the signal power (S) to the noise power (N). The higher the S/N the better the signal quality.
The polarization axes of a geostationary satellite antenna are usually adjusted perpendicular to the equator. Because of the almost spherical shape of the earth, earth station antennas not located at the same longitude of the orbital position of the satellite have an inclination in polarization angle when looking to this satellite. The skew angle is the angle that has to be adjusted to compensate this difference in orientation.
A focused antenna pattern of a satellite antenna sent to a limited geographical area, to deliver certain transponder signals to these defined areas.
An electronic device which modulates voice, video and data signals into electromagnetic waves and radiates them into the atmosphere by using an antenna.
Very Small Aperture Terminal. It is a two-way satellite ground station or a stabilized maritime VSAT antenna with a dish antenna that is smaller than 3 meters. The majority of VSAT antennas range from 75 cm to 1.2 m. Data rates range from 4 kbit/s up to 4 Mbit/s; some upgraded modules can even reach a max downlink of up to 16 Mbit/s.
Western Limit Switch.