CDMA Code Tracking Loop Based on Digital Matched Filter And Multipath Timing Error Combing
Zou Xi · Journal of Circuits and Systems · 2003
PN code tracking is investigated for direct-sequence code division multiple access (DS-CDMA) cellular mobile radio such as WCDMA. Two chip clocks with half-chip phase offset are used to sample the received signals, which are de-spreaded by two digital matched filters (DMF) respectively. Pilot correlation outputs at integer sampling instants are used for channel estimation and multi-path search, and those outputs at half-integer sampling instants for timing error extraction. Taking advantage of the inherent diversity with maximal ratio combing (MRC) based on selected multi-path components, the code tracking loop performance is improved with reduced hardware complexity.