Glossary - B

Backhaul
a terrestrial communications channel linking an earth station to a local network or population centre
(satellite communications)

Backoff
the reduction of input power to a high power amplifier (HPA) so that the amplifier operates in a more linear region
(earth station technology, spacecraft technology)

Band pass filter
a circuit or device which allows frequencies in a desired band through but which attenuates signals of higher and lower frequencies
(communications)

Bandwidth
the amount of frequency space occupied by a signal
(communications)

Barycentre
the common centre of mass about which two or more bodies orbit
(orbital dynamics)

Beacon
a low power carrier transmitted by a satellite which allows a ground station to accurately point its antenna at the satellite; beacon signal transmissions also often carries telemetry
(satellite communications)

Beam
the concentrated pencil of radiation produced by an antenna
(technology)

Beamwidth
the angular width of an antenna beam; usually the 3 dB beam width at which the antenna gain is 3 dB below that on the boresight
(technology)

Bearer channel
a channel from which a user derives multiple channels
(communications)

Bent pipe
term used to describe a transponder which only amplifies and frequency converts a signal, but does not perform any other processing such as regeneration
(satellite communications)

Big LEO
low earth orbit satellite for voice and data communications
(orbits)

Bipropellant
rocket propellant consisting of a fuel and oxidiser which are stored separately but which are mixed and burnt together in the combustion chamber of the rocket motor
(launcher technology, spacecraft technology)

Bird
slang expression for a satellite
(spacecraft technology)

Bit error rate
the rate at which errors occur in the transmission of data over a particular channel
(communications)

Bit rate
the speed of a digital transmission, expressed in bits per second
(communications)

Black hole
a region of spacetime that has such a strong gravitational field that nothing (including light) can escape it
(astronomy, astrophysics, physics)

Blazar
an active galactic nucleus (AGN) with a relativistic (near light speed) jet of ionised matter pointing directly at the observer which makes the blazar appear much brighter across the electromagnetic spectrum than it would do if it was pointing in another direction
(astronomy, astrophysics)

Block downconverter
a unit, which is normally located at the antenna feed behind the LNB, which converts the received frequency down to L band (approx 1 GHz)
(earth station technology)

Block upconverter
a unit often used in VSAT terminals which converts the L band (approx 1 GHz) output of a modem up to the transmit frequency (usually C band, Ku band, X band or Ka band) and boosts the power for transmission
(earth station technology)

Boresight
the direction along the principal axis of an antenna, usually the direction of maximum gain or the direction along the principal axis of an optical system
(technology)

Bouquet
a group of TV channels marketed by the same organisation and which can be decoded by a single smart card; the channels though, may originate from different broadcasters
(broadcasting)

Broadband
high data rate, usually taken to mean higher than 64 kbps or 2 Mbps, though there is no generally accepted definition
(communications)

Broadcast
the transmission of a signal to all terminals in a service area/network or the signal itself
(broadcasting)

Broadcast storm
multiple simultaneous broadcasts that can absorb available network capacity and can cause network time-outs
(broadcasting)

Brown dwarf
a substellar object with a mass between that of a large planet and a small star that is not massive enough to sustain nuclear fusion reactions in its core
(astronomy)

Bundling
the practice of offering several services as a package
(broadcasting)

Business TV
private use of television within an organisation to keep staff up to date with new product releases, events and company news
(communications)