Advantage of matched filter over correlator if there is any?

[SherlockBenedict]

I have seen this question asked so many times but I couldn't find the required answer. Both matched filter and correlator seem to have the same expression. Matched filter seems to be implemented using filter while correlator can be done by mixing them and averaging. Both need synchronization for maximum SNR. But most of us prefer matched filter and I don't know why. Is there any specific advantage for this Matched Filter? Or is there anything like -" Matched filter is intended for some kind of systems and correlators are intended for some other kind of systems" ??

Thanks

 

[iVenky]

The matched filter and correlator are same only at the instant 'Tb'. If you write the expression and see you would understand that the pulse shape at the output of both would be different. Anyway both would have the same value at 'Tb'. From what I see matched filter output would keep on varying fast (if your input is RF signal) whereas correlator output would look more like a ramp output slowly increasing. So incase if there is a slight variation in the timing instant matched filter should give you more degradation comapred with correlator. Though I am not sure about the advantage of matched filter over correlator.

 

[Shug]

I think matched filters are mainly used for ease of analysis; they make more sense from a filtering/convolutional perspective. Because both yield the same result and both have the same computational complexity, there is not much in implementation/performance that changes between the two.

Also, iVenky, I do not think the two are different. The integrator in the correlator is from 0 to T, so a proper correlator will only consider that window, which is the same as the matched filter window.

 

[iVenky]

Hello Shug.The shape of the waveform at the output of both would be different. Only at exactly t=Tb they both have the same value.