Method and apparatus for generating multiple matched-filter pn vectors

Abstract

A vector generator generates one or more pseudo-random noise PN sequences as matched-filter PN vectors for a matched-filter correlator of a code division, multiple-access (CDMA) demodulator. The period and clock of the local PN code sequence may be employed as a time reference, and each matched-filter PN vector has a known code-phase offset with respect to the local PN code sequence. Matched-filter PN vectors having a chip-length on the order of a data symbol period, such as 64-chip sequences, are generated within a short period of time compared to the period of the local PN code sequence. A state of the local PN code sequence is periodically captured from the local PN code sequence, which state is employed by a PN generator generating a similar PN code sequence but clocked at a higher rate. Consequently, a series of offset PN code sequences are generated in advance of the local PN code sequence. Combined with single or parallel offset masking, any desired matched-filter PN vector may be generated from the offset PN code sequences within a short period when compared to the period of the local PN code sequence. The generation time of each matched-filter PN vector may be 1-chip period in duration. A vector correlator of a RAKE receiver may employ the vector generator in a CDMA communication system. Consequently, the vector generator provides the vector correlator with matched-filter PN vectors for a matched-filter, multiple-finger search. The vector generator allows for time-multiplexed generation of the matched-filter PN vectors.