An embodiment of the present invention provides an automatic gain control
system for a wireless receiver that quickly differentiates desired in-band
signals from high power out-of-band signals that overlap into the target
band. The system measures power before and after passing a received signal
through a pair of finite impulse response filters that largely restrict
the signal's power to that which is in-band. By comparing the in-band
energy of the received signal after filtering to the total signal energy
prior to filtering, it is possible to determine whether a new in-band
signal has arrived. The presence of this new in-band signal is then
verified by a multi-threshold comparison of the normalized
self-correlation to verify the presence of a new, desired in-band signal.
