Satellite Communications (Satcom) Flashcards
Who are the three most common providers of uplink and downlink for aviation use?
Globalstar
Inmarsat
Iridium
Satellite systems work in:
Duplex or Simplex
What does duplex mean?
Duplex means that two different frequencies are used to transmit and receive info
What is Phase Shift Keying (PSK)?
a digital modulation process which conveys data by changing (modulating) the phase of a constant frequency carrier wave.
What is a Simplex?
Transmit only system
No return is given
Duplex system allows for what to happen simultaneously?
transmit and receive capability
Frequency FROM aircraft TO satellite is known as:
Uplink
Frequency TO the aircraft FROM the satellite is known as:
Downlink
Three common frequencies used with Satcom are:
UHF, SHF, and EHF
What three segments is the Satcom system divided into?
The Space Segment (Space Vehicles)
The Control Segment (Communication and control of Satellites)
The User Segment (Those using the satellites for communication)
A satellite transponder consists of:
A low noise amplifier, mixer, local oscillator, and a power supply
What does the Low Noise Amplifier do?
Receives the uplink and provides the signal to the mixer
Along with the uplink, what else does the mixer receive?
A local oscillator input
Signals sent from the satellite transponder are:
Multiplexed
What is Multiplexing?
A method of dividing several simultaneous signals into small pieces, which can be transmitted on a single channel.
A single satellite contains many transponders, each of which do what?
Retransmits multiplexed signals
What does demultiplexed mean?
It’s the extracting of signals
Satellites use what system?
A Phased Array System
What is included in a Phased Array system?
An array, or group of antennas, that are connected together with phase shift networks
Phased arrays exhibit high:
gain and directionality
By controlling the phase shift networks, the pattern can be:
changed without need to physically move or re-aim the antenna
What is InMarsat?
(British sat company)
An international corporation providing two-way communication services to governments, aid agencies, media outlets, and businesses with a need to communicate to remote regions or where there is no reliable ground network.
The InMarsat system uses what components?
Two satellite data units (SDU)
Two radio frequency units
And several other LRU’s with a sophisticated antenna system (which contains its own LRU’s)
The Satellite Data Units (SDU) are connected with what systems?
The Inertial Reference Systems (IRS)
The automated Dependent Surveillance System (ADS-C)
And the audio systems
The IRS connection allows Inmarsat to determine what?
aircraft location in order to control the radiation/ reception pattern using the Phased Array.
What is GlobalStar?
A low earth orbit constellation consisting of 44 satellites for satellite phone and low speed communications
The GlobalStar space vehicles provide signal coverage for most of where?
The Northern Hemisphere
What other services are available through GlobalStar?
Internet and private network connections, position location, and texting.
The GlobalStar system covers where?
Most continental areas for data services
The aircraft on-board GlobalStar system consists of:
A transceiver, antenna, and control panel or headset
Data terminal devices are available with integrated:
GPS receivers that provide position information and connections to computers and printers.
What is Iridium?
a US based company that operates 66 satellites in low-earth orbit
Iridium is a cross-linked system to provide voice and data communication where?
Worldwide
And it is the world’s largest commercial constellation
What type of broadcast satellite system is Sirius?
Downlink only
The Sirius XM system uses:
Two geo-stationary satellites
What is one issue that can be had with Sirius systems?
Propagation control which causes an echo because of the time delay in the transmitting and receiving of waves
