Delay-locked loop with correlation branch selection

Mobile communications based on code division multiple access (CDMA) and global positioning systems (GPS) are considered or already in operation. In spread spectrum systems the delay-locked loop (DLL) is widely used to track the spreading code. Normally a design tradeoff between tracking accuracy and robustness against disturbances is required. Extended tracking range DLLs (ExtDLL) using more than two correlators increase the robustness but are less accurate. An algorithm based on the ExtDLL is proposed offering both robustness and good accuracy by selecting only correlation branches with an useful control signal. The new algorithm shows a very good performance at medium to high signal-to-noise ratios (SNR). With increasing SNR it approaches the classical DLL performance for accuracy and is more robust than the classical DLL and the ExtDLL.