FAST SLEWING PSEUDORANDOM NOISE SEQUENCE GENERATOR

摘要

One or more loadable PN generators are controlled by a DSP or microprocessor in conjunction with a free-running counter which maintains a reference offset count. The PN generator will typically be part of a finger or searcher. Each PN generator is comprised of a loadable linear feedback shift register (LFSR) or its equivalent, a loadable counter for maintaining an index of the state of that particular PN generator, and a slew control device capable of receiving a slew command and controlling the LFSR and index counter to enact an advance or a retard of a certain offset distance. The speed increase is effected by DSP control. A table of LFSR states and corresponding index numbers are stored in memory. These LFSR states will subdivide the tot al possible number of possible states. It is advantageous to evenly space the stored states around the PN circle. The fast slewing is enabled by the DSP in two-step process. First the PN generator is loaded such that it "jumps" to the closest state using the table, then the P N generator's slew control is used to slew the rest of the way.