A nonzero intermediate frequency likelihood acquisition scheme for CDMA system

A nonzero intermediate frequency (IF) likelihood acquisition scheme for PN codes is introduced in this paper. The received signal is first downconverted to IF, and then direct sampled in IF using a 1-bit A/D converter. After the digitalization, the sampled data is detected using a hybrid likelihood acquisition scheme. Using this structure, problems, due to large noise figure of the analog mixer or active filters or due to amplitude and phase imbalance between low-frequency in-phase and quadrature-phase channels, can be avoided. An algorithm which allows easy implementation of the acquisition scheme is also derived. The performance and algorithm are verified by computer simulation.