Just imagine the communication that occurs between a satellite orbiting the earth and the receiving station on earth.
Clearly, in order for that communication to be successful, the signal needs to be received at the earth station with enough SNR (signal to noise ratio) for the signal to be intelligently received and acted upon at the earth station.
In order for the Satellite designers and the Earth Station designers to do their jobs, they must work together to ensure that transmitting satellite transmits with enough power for the receiving station/dish to understand the signal. This would be simple if we could assume that the receiving dish receives all of the power that the satellite transmits, but that would not be a good assumption. There are various things encountered by the signal during its trip between the satellite and the receiving station which each reduce the power of the signal by a small amount. The transmitter must know how much its transmission will be reduced by all of those things, and account for those losses by boosting transmitting power by that amount so that a reduced received power will still be sufficient for the receiving station to get sufficient SNR in the signal.
A Satellite Link Budget is an accounting of all of the gains and looses that signal will experience in space between a transmitter and a receiver.
So, what are the things that may increase or decrease the power of a signal during its journey between a transmitter and a receiver?
Rain is one example of something that reduces the power contained in the signal. A designer must assume that it will always be raining during the transmission, or they will end up with a system which is only effective on non-rainy days. This would not be a good design.
The easiest way to account for gains and losses is with a proven computer tool like SatMaster from Arrowe. Rain models from the ITU (International Telecommunications Union) provide a viable methodology for assessing rain attenuation in microwave and millimeter wave bands.
And, what are some of the other things that will reduce transmitted power? These are all great questions, beyond the scope of this blog.
If you design transmitters, or if you design receivers, or if you simply want to learn more about Satellite Link Budgets, consider taking the upcoming ATI course Satellite Link Budget Training on the Personal Computer – GEO and non-GEO, L through Q/V bands. You can learn more about this course and register to attend the course here.