Basics of Satellite Link Emulator

This page covers satellite link emulator basics. It mentions application note covering how to use satellite link emulator from dBm corporation to model the satellite channel for testing of satellite ground station equipments.

As we know satellite communication systems use different frequency bands for communication such as L Band(1-2GHz), C band(4 to 8GHz), Ku band(12 to 18GHz) and Ka band(26.5 to 40GHz). Portion of L band is used in Inmarsat.

satellite communication system

The figure mentions two modes used in satellite communication i.e. star and mesh. The link between VSAT terminal to Satellite and from satellite to VSAT terminal(i.e. ground station) is simulated for testing purpose. In such testing, real time testing with satellite is not needed and hence considerable amount of time can be saved and same test performance can be achieved.

In Iridium satellite systems different bands are used between user to satellite, gateway to satellite, satellite to gateway and between satellites(inter satellite). Inter satellite link uses 22.55 to 23.55 GHz. This satellite to satellite link can also be simulated using satellite link emulator.

As we know there are different satellites for different applications viz. communications satellites which are used for VSAT based communication, remote sensing satellites, weather satellites, GPS satellites etc. There are two major elements in all the types of satellites. They are payload and bus.

Payload: It is a equipment which satellite needs to do the job. Payload includes cameras, antennas, radar and electronics. All the satellites have different payload. Example: communication satellite has antennas as payload, while weather satellite has cameras and so on.

BUS: It is part of satellite which carries payload and its equipments into the space for launching. Bus provides power and keeps all the parts together. It also has equipments for satellite to have communication with the earth station equipments.

Application note-How to use Satellite Link Emulator from dBm corporation

dBm corporation provices SLE9000 series of satellite link emulators for testing of VSAT and earth station equipments in simulated real time mode. This application note covers features of dBm satellite link emulator.

The satellite link emulator provides RF link emulation for VSAT terminal or payload development. SLE is used for following applications.
• Earth Station testing
• Satellite payload testing
• Mobile transceiver testing
• Satellite system integration tests
• Satellite to UAV tests

It provides emulation for following links and orbit modes:
• earth to satellite to earth (in mesh mode)
• earth to satellite links
• Low Earth Orbit
• Medium Earth Orbit
• Geostationary orbit and Geosynchronous orbit
• satellite to satellite links

satellite link emulator set up

Satellite link emulator can simulate propagation delays, path loss, flat fading, phase shift and different doppler frequency shifts. Optional features such as multipath fading (rician and rayleigh) as well as AWGN are available. In multipath fading upto 6 paths can be simulated per channel.

The dBm Corporation offers external frequency converters to extend the testing coverage in wide variety of radio frequency bands used in satellite applications.

dBm satellite channel emulator comes with easy to use GUI software which helps in setting up various parameters in handy manner. It helps in programming of all the orbits as well as any earth station co-ordinates. Various satellite systems such as Iridium®, ICO®, Globalstar® and Inmarsat® can be simulated. The GUI software runs on any windows based computer.

Figure-2 depicts test bed for testing VSAT ground equipments. Earlier days TLT(Test Loop Translator) was used which houses only LO which used to convert 6 GHz frequency to corresponding 4 GHz frequency. Now-a-days satellite link emulator introduces all sorts of impairment such as frequency offset, phase noise, time delay, channel models etc. to simulate the real time test scenario.

The other manufacturer/vendor of satellite link emulator is Polaris. They have various models PSLE-L-10D, 100D, 200D and so on.

Test and Measurement Equipments

RF and Wireless Terminologies