Display interference from a LEO constellation on a GEO to Ground Communications Link on the Spectrum Analyzer

This is the second part in a series. Refer to LEO / GEO SATCOM Interference for Part 1.

A Communications scenario is built in STK to model LEO interference on a Geostationary satellite to ground link. The LEO satellite constellation is built by using the Walker Tool available through the SATPRO module in STK. Each LEO satellite has a multibeam transmitter as an interferer. The center portion of the figure below shows the 3 dB contours of the multibeam transmitter surrounding a ship receiver.

A CommSystem object is used to process the interference of these LEO transmitters on the desired space-to-ground link represented with a green line in the figure below. A red line represents the interference link. The graph on the right shows the C/(N+I) or Carrier to Noise Plus Interference Ratio (in red) at the time of maximum interference (about 15 dB compared to the static C/N in green).

The Spectrum Analyzer echoes what is shown in the graph and 3D display. The Peak Power of the LEO interferer spectrum exceeds the GEO transmitter spectrum by about 15 dB and the C/I shows the same. The frequency axis spans the receiver bandwidth (in MHz) around the center frequency (in GHz). The vertical scale is dialed to -160 dBW for the lower Y-axis limit.

If you have questions or want to explore more, come by and see me at SATELLITE 2018. I'll have this scenario, and others up and running at Booth 1143. Hope to see you there!

Systems Tool Kit (STK)

Modeling and simulation software for digital mission engineering and systems analysis.


Design and operate satellite systems with specialized propagators, attitude profiles, and satellite engineering tools.


Model and analyze real-world dynamic RF and optical communications.