Modulation Loss

[happycj]

First of all, I find the materials (esp the tutorial notes) in this site are of extremely high quality. I believe there are many gurus of communication field in this forum who can help me.

I recently go through some proposals on satellite telemetry and ranging budgets, and find a term called "modulation loss". It is essentially a term to convert from C/N to S/N in the receiving system.

Do any one have a table or formula to show the "modulation loss" for different types of modulated signal (like FM, PM and others)? I need that to check the proposed figures.

Thanks

[charan langton]

Not sure what this modulation loss may be. It could be the loss due to modulation though a non-linear amplifier which is what satellites use. For a QPSK signal which is the most common constant envelop signal use in satellit elinks, this number can be around 1.5 to 2 dB.

Charan Langton

[chico128]

In the case of telemetry if the data is on a sub carrier which is then PM modulated on to the main where there is a ranging signa alsol. The modulation loss terms are subtracted from C/N to get the correct S/N for the telemetry channel. This is done the most in the Air Force SGLS specifications for thier tracking stations.

chico