In order to make my question more clear and give more details I'm trying to understand the processing signal procedure in radars,i understood till this moment that a transmitter generates a signal called transmitted signal with a center frequency and then when this signal meets a target an echo signal reflected to radar and captured with a received stage including many RF and non RF components.After amplification and noise rejection with LNA a mixer is used to melange received and transmitted signal to produce a signal called video signal and then the signal processing stage take place. My question are : can anyone explain me what's the role of the matched filter in radar signal processing stage what are the alternatives methods?
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$\begingroup$ Radar receiver produces a video signal that is then processed further in a signal processing stage? Are you using the correct English terminology or are you mis-translating something that you read in another language? $\endgroup$– Dilip SarwateJul 18, 2018 at 1:15
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The simple answer is the matched filter increases the signal to noise ratio of the reflected return signal.
As the signal propagates from transmitter, the power that impinges on the target is proportional to $1/r_{target}^2$. The reflected energy back to the transmitter is also proportional to $1/r^2$, so the received energy is proportional to $1/r^4$.
The received back echo power is very small and the matched filter maximizes the deflection of the echo with respect to the noise in the receiver.
This is a simple explanation. There are many types of RADAR, and there are additional ways to make the echo stand out with respect to the noise of the system and the clutter echos present in all real systems
Those additional ways that are specific to the different kinds of RADAR systems to make the echo discernible. There are various ways to modify a matched filter for a specific kind of applications but it would be hard to say they were alternative to a matched filter. The underlying optimality characteristic of a matched filter justifies few alternatives.