Measurement & Test - Satellite Ground Station Test

 

In these tutorials we will look at the various component parts that make up a satellite ground station and the typical practices that engineers employ during satellite ground station engineering projects.

 

Measurement and Test Equipment

Power Meter
To determine how much power is being transmitted from the antenna a power meter can be connected to the waveguide coupler at the output of the HPAs. The power meter is connected via sensor that has a calibrated conversion factor for the frequency in use. If the waveguide coupler is a 50dB coupler then the signal at the power meter is 50dB lower than the signal entering the feed. Based on this the EIRP can be easily calculated using the antenna gain.

Spectrum Analyser
To visualise the signals in the transmit and receive paths, a spectrum analyser is used which can measure the signal levels and determine the C/No of the signals as well as absolute signal levels.

Signal Generator
For test purposes, a signal generator can be used to inject a Carrier Wave, Continuous Wave (CW) signal or Clean Carrier, which has no modulation. This signal is very stable and can be used for measurements throughout the transmit and receive chains. Care should be taken of course not to inject a CW signal into the transmit path whilst the HPAs are transmitting as the signal would be transmitted to the satellite and could cause interference. Signal generators at IF frequencies are much cheaper than those at RF frequencies due to the cost of the components required to make them.

Test Loop Translator (TLT)
A test loop translator converts the transmit signals to receive signals either before or after the HPA/LNA. The purpose of the TLT is to provide a loop which can be used for testing the complete transmit and receive chains or monitoring the uplink independently of the receive.

In the next Tutorial we will look at System Enhancements.