Propagation Losses Considered in Satellite Communications Toolbox

I try to make an interference study between two satellite and a ground station and I was looking into this example : https://fr.mathworks.com/help/satcom/ug/interference-from-satellite-constellation-on-comms-link.html. I tried to understand which propagation losses are considered in the Link and sigStrength functions.

On a simpler example I used 2 satellites in the same position, with a ground station at 90° of elevation so the interfering power should be equal to the received power, using the link budget equation :

I calculated the free space path loss : with r the distance in m.

However, there are still 3.72 dB of losses remaining that are not FSPL or due to the transmitter or receiver (SystemLoss and preReceiverLoss are set to 0). I even tried placing the satellites at different altitudes, but the losses remained the same (3.72 dB).

I considered rain and atmospheric losses, but at an altitude of about 500 km and a frequency of 8 GHz, these losses are less than 0.5 dB.

Do you know what hypothesis and losses are considered in this Toolbox ?

Answer 1

[Mike McLernon]

The link() and sigStrength() functions in Satellite Communications Toolbox account only for free space path loss when calculating a propagation loss.

A few things to note as you search for that 3.72 dB:

1. Both Transmitter and Receiver objects have a SystemLoss.
2. Make sure you are accounting for the transmitter and receiver antenna gains.
3. Make sure you are pointing the transmitter and receiver antennas at one another.