Suppressed carrier tracking when quadrature PN spreading

The DS-SS CDMA standard for digital cellular communication (IS-95) employs quadrature PN spreading. Conventional carrier phase detectors using the two despread quadrature channels produce an untrackable error term proportional to the cross correlation between the inphase and quadrature PN codes. Tracking loops capable of circumventing this issue are defined and analyzed. These loops support QPSK throughput with carrier tracking performance characteristic of BPSK. Further, a new correlation loss is identified which is negligible for moderate spreading ratios but can be substantial for small ratios.