Patent ID: 7899109

Claim:
A system for determining a code phase error of a multimodal spread spectrum signal spread by a multimodal code being a spread spectrum chipping code having a multimodal autocorrelation function having modal peaks, the system comprising, a demodulator for carrier demodulating the multimodal spread spectrum signal into multimodal quadrature signals, a generator for generating multimodal code replicas of the multimodal code, the multimodal code replicas being offset in time to the multimodal code by the code phase error, a correlator for receiving the multimodal quadrature signals and correlating the multimodal quadrature signals into multimodal quadrature correlations by the multimodal code replicas, and a tracking system for receiving the multimodal quadrature correlations and for detecting a multimodal code envelope coherently encompassing the modal peaks and for identifying a mode of the modal peaks for generating the code phase error, wherein the tracking system comprises: a multimodal code envelope detector for determining the multimodal code envelope from early and late versions of the multimodal quadrature correlations respectively using early and late versions of the multimodal code replicas, a multimodal code envelope tracking-filter for receiving the multimodal quadrature correlations and the multimodal code envelope and the mode, the multimodal code envelope-tracking filter for providing a multimodal code error covariance and an envelope covariance and a multimodal code envelope range error and the local multimodal code range error state estimate, a mode identifier for receiving the multimodal code error covariance and the envelope covariance and the multimodal code envelope range error and the local multimodal code range error, the mode identifier generating the mode, and a phase error calculator for receiving the mode value and the local multimodal code range error and for providing the code phase error.