Editing Satellite modem (section)

=== Analog tract ===
After a [[digital-to-analog conversion]] in the transmitter, the signal passes through a [[reconstruction filter]]. Then, if needed, frequency conversion is performed. 

The purpose of the analog tract in the receiver is to convert signal's frequency, to adjust its power via an [[automatic gain control]] circuit and to get its [[complex envelope]] components.

The input signal for the analog tract is at the [[intermediate frequency]], sometimes, in the [[L band]], in which case it must be converted to an IF. Then the signal is either [[Sampling (signal processing)|sampled]] or processed by the four-quadrant multiplier which produces the complex envelope components (''[[I and Q|I, Q]]'') through multiplying it by the heterodyne frequency (see [[superheterodyne receiver]]).

At last the signal passes through an [[anti-aliasing filter]] and is '''[[sampling (signal processing)|sampled]]''' or ('''digitized''').