RF

Link Budget    

Simply put, Link budget is a kind of balance sheet from a source to a destination in terms of power loss and gain.

Every component can fall into one of the two categories in terms of input/output energy balances. Some devices cause energy loss (power loss) as a signal goes through (these devices are called passive device) and some devices produce energy gain as a signal goes through (these devices are called active device. Be careful, even these devices cannot create any new energy. It is against the law of physics. They are pulling some energy from somewhere else and add it to the signal).

Suppose you have multiple devices connected together as shown below and some are activce and some are passive. What would be the sum of the energy balance between the start (point a) and end (point h) ?

As more specific example, let's assume that you have following components connected together and engergy gain or loss for each specific block is as follows. What would be the total energy balance ?

This 'total energy balance' in this question is called 'Link Budget' and it can be calculated as follows. (Math is very simple)

For practical tutorial, refer to Lecture on Link budget (YouTube)