Hierarchical delay lock loop code tracking system

Abstract

A receiver of signals modulated by pseudorandom noise that uses a hierarchy of delay lock loops (DLLs) to maintain code lock. Each DLL in the hierarchy produces a control signal represenative of a timing mismatch between the incoming signal and an internally generated pseudorandom noise code, preferably by correlating the incoming signal with early and late instances of the code and subtracting the late correlation from the early correlation. The early correlation is advanced relative to the late correlation by successively shorter spacings in successively lower DLLs in the hierarchy. In each DLL, the control signal is transformed to a code phase signal for adjusting the timing of the code generator. In the lower DLLs, this code phase signal is compared to the delay signal of the immediately higher DLL and adjusted accordingly. This receiver combines the immunity to random noise, associated with short spacings between the early and late correlations, with the immunity to sudden receiver motion associated with long spacings.

Dependencies are inferred from the claim text.