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Early-Late correlator for DLL

Started by Ravi Srikantiah November 9, 2004
Hi,

An early-late correlator is used by most rake receivers for fine 
tracking. The way it is done, is to have an early code, an ontime code, 
and a late code correlated with the incoming stream, where the delays 
between the early-ontime, and ontime-late codes are equal. Now, it is 
said that the ontime position is "correct", when the result of the cross 
correlation with the early code is equal to that of the late code. To 
me, this does not seem obvious... This would happen only if the cross 
correlation function was an even function. What guarantees this?

Appreciate your help.

- Ravi
Duh! Figured this out.
It's the autocorrelation that's being performed here... And that's an 
even function. The only caveat is that the tracking needs to be done 
over symbols that have the same value.

Ravi Srikantiah wrote:

> Hi, > > An early-late correlator is used by most rake receivers for fine > tracking. The way it is done, is to have an early code, an ontime code, > and a late code correlated with the incoming stream, where the delays > between the early-ontime, and ontime-late codes are equal. Now, it is > said that the ontime position is "correct", when the result of the cross > correlation with the early code is equal to that of the late code. To > me, this does not seem obvious... This would happen only if the cross > correlation function was an even function. What guarantees this? > > Appreciate your help. > > - Ravi