What is Spectrum Analysis

In order to see all of the signals that are being transmitted over a satellite, or indeed over any radio frequency system, the most effective tool for visualising them is a spectrum analyser.

These tools give a graphical representation of a portion of radio frequency spectrum which can be selected and zoomed in on. The centre frequency of the display is set by the user and the span of frequencies shown is also set along with some other parameters.

The user chooses these settings in order to see the signals of interest and then measure them accurately.

Spectrum Analysers

These tools are very expensive and some engineers would swear they come with added bricks because of the size and weight of them. The main aim of an analyser is to measure a signal in terms of C/No and therefore check a signal against the expected C/No from the link budget.

Because the analyser shows the signal in the frequency domain (x axis) as opposed to an oscilloscope which would show the signal in the time domain (x axis) the exact frequency can be determined easily to identify any differences in expected an actual results.

The y axis measures amplitude just as an oscilloscope does but in dB rather than volts.

Frequency Spectrum

The universe has a vast frequency spectrum which starts at DC (0 Hz) and goes up, way up through radio frequency through light and beyond. We are only interested in radio frequency which contains our radio stations, terrestrial television channels, two way radios, mobile phones, all satellite communications and line of sight communications.

In order to see these signals the only way is to use a spectrum analyser. As the technolgy improves these devices are becoming cheaper and smaller. Now handheld analysers are finally available which makes life a lot easier when working in the field rather than a lab.