what Bandpass filter is doing in Energy Detector

Hello there, Since we all know that energy detection is blind technique that estimates the presence of signal in the spectrum. I would like know what bandpass filter does in energy detection as we dont have any information about signal and band, we want to scan for primary users. If it is really required in energy detection then what would be the bandwidth of frequency spectrum we wish our filter allow. thanx

Talha

[ayman osama]

did u have solution for this problem because i have same problem???????????

[Arsalan]

If this is a cogntive radio problem. I guess the BW of the filter should match that of the signal which is to be transmitted.

[Youssef Khmou]

what kind of signal is that : random, deterministic, ergodic...? you have to know some preliminary information abut the signal, at least the Sampling frequency Fs, so as to correctly compute the Spectrum,PSD with Discrete Fourier Transform, from there you can configure the filter .