Patent ID: 7555033
Filing Date: 2009-06-30
Classification: G01S,H04B,H04L

Abstract:
1. A system for detecting a broad correlation envelope and a narrow correlation envelope of a received signal comprising a carrier modulated by a spreading code, the system comprising, a splitting means for splitting the received signal into an inphase signal and a quadraphase signal, the splitter means further for coherently demodulating the received signal by mixing the received signal by a carrier replica, the splitter means further for coherently despreading the received signal by mixing the received signal by code replicas of despreading codes, the despreading codes and code replicas defining a code phase error between the received spreading codes and code replicas, the splitting means serving to demodulate in quadrature and despread and split the inphase signal and the quadraphase signal into I and Q inphase signals and I and Q quadraphase signals for each of the code replicas, a correlation means for generating narrow and broad correlation values from broad and narrow code replicas of the code replicas and from the I and Q inphase signals and I and Q quadraphase signals, the narrow correlation values generated from the I and Q inphase signals, the broad correlations values generated from the I and Q inphase signals and I and Q quadraphase signals, the narrow correlation values defining a narrow correlation envelope, the broad correlation values defining a broad correlation envelope, a replica code generator means for receiving the code phase error and for generating and shifting the code replicas in time for generating and aligning a prompt code replica of the code replicas with the received spreading code for coherently despreading the received signal in synchronism between the prompt code replica and the spreading code, the replica code generator generating the narrow code replicas and the broad code replicas of the code replicas, a discriminator means for generating the code phase error from the narrow correlation envelope and the broad correlation envelope, the discriminator means for adjusting the code phase error over differing narrow and broad correlation values, and wherein, the narrow code replicas comprise a narrow early code replica and a narrow late code replica, the narrow early code replica and the narrow late code replica are separated in time by a narrow time duration, the broad code replicas comprise a broad early code replica and a broad late code replica, the broad early code replica and the broad late code replica are separated in time by a broad time duration, the broad duration time is greater than the narrow duration time, and the narrow correlation values linearly changing over differing values of the code phase error when the code phase error is less than the narrow time duration.