STK/Communications Receivers & Transmitters

In this exercise you will work with STK/Communications transmitter and receiver objects to model communications links. You will also get some practice in creating a custom graph.

Note: You will need a valid STK Professional Edition and STK/Communications license.

Create a Receiver and Transmitter

  1. Create a scenario, and name it Comm.
  2. Create a facility, name it Customer, open its Position page, and set the following Geodetic parameters:
  4. Click OK, then use the Orbit Wizard to create a Geosynchronous satellite with a Subsatellite Point of 270 deg. Name it GEO.
  5. Attach a sensor to the satellite, and name it FOV. Open its Definition page, and increase the Cone Angle to 90 deg. Click OK.
  6. Select the facility in the Object Browser, then double-click in the Object Catalog to add a receiver. Name it GndRcvr.
  7. Open the receiver's Definition page, and make certain that the Model Type is set to Simple Receiver Model and that the Frequency Auto Track on the Model Specs tab and Bandwidth Auto Scale on the Filter tab are checked. On the Model Specs tab, Set G/T to 6 dB/K, and click OK.
  8. Select the satellite in the Object Browser, then double-click in the Object Catalog to add a transmitter. Name it Downlink.
  9. On the transmitter's Definition page, make certain that the Model Type is set to Simple Transmitter Model, and enter the following settings:

  10. On the Model Specs tab:

    On the Modulator tab:

  11. Click OK.

Determine Link Performance

  1. Select the transmitter in the Object Browser and click to launch the Access tool.
  2. In the Associated Objects area, select the receiver (which is attached to the facility), then click Link Budget... in the Reports area.
  3. In the Link Budget report, find the bit error rate (BER) at 10 pm (22:00). Leave the report open.
  4. Open the Orbit page for the satellite, change its Inclination to 10 deg and click Apply.
  5. Now refresh the Link Budget report. You will see that there is some improvement in the BER at 10 pm.
  6. Open the Constraints - Comm page for the receiver, set the Eb/No Min value to 11.8 dB, and click Apply.
  7. Refresh the Link Budget report again and observe the approximate 9-hour gap in coverage that starts at approximately 5:25 am.
  8. Close the report, and return to the Access page for the transmitter. Click Report & Graph Manager ....
  9. In the Style area, select My Styles. Click to create a new graph style. Rename the new graph style Noise Rate.
  10. On the Content page, open the Link Information tree to expose the communications link parameters that can be graphed.
  11. Select Eb/No, and use the right arrow button to move it into the Y Axis area.
  12. Click OK to dismiss the Content page.
  13. Double-click the Noise Rate graph style and observe the variations in link performance over time due to the satellite's inclined orbit. Note that there are no Eb/No values lower than 11.8, since they are excluded by the Communications constraint that you set.
  14. Close the graph and the Report & Graph Manager.
  15. Return to the Constraints - Comm page for the receiver, and remove the Eb/No constraint. Set a Bit Error Rate Max constraint of 1.0e-8 and click OK.
  16. On the transmitter's Access page, create a  new Link Budget report.  Notice that there is only access when the BER is 1e-8 or lower.
  17. Zoom in on the satellite in the 2D Graphics window. Note that only the northern portion of the ground track is highlighted to indicate access from the transmitter to the receiver.