Access Code Correlator

Original Post: Access code correlate (eGroups Msg. 157) Date: 2000-01-07

In the blutetooth spec.V1.0B, pp48 it states ,"In the receiver of the Bluetooth unit, a sliding correlator correlates against the access code and triggers when a threshold is exceeded. This trigger signal is used to determine the receive timing."

2 questions that may arise from this statement are:

What's is the sliding correlator and it's main functions, in baseband, and is there any standard on it?
It's seems that there isn't any specific and clear "trigger theshold" data in the spec., so what's its appropriate vaule?

Correlation is a very useful method to match a known signal with a possible future one.

The method is to use the known signal as a 'match pattern' to match the uncertain signal, if the correlation value exceeds the trigger level, we can say we have found that signal.
When the signal is coming, the correlation value's trend in the sliding correlator is from low to high. When the signal is passing by, the correlation value's trend in the sliding correlator is from high to low.

The Trigger level uses the Access Code located in the first part of the baseband packet. When the receiver is triggered it means that the receiver has found the packet header. So the slave can use this time to adjust the native clock.