Patent ID: 6314128
Filing Date: 2001-11-06
Classification: H04B

Abstract:
A synchronized receiver for a spread-spectrum communications system, said system having a transmitter for generating a data-modulated carrier signal encoded with a predetermined discrete-stepped, cyclical pseudo-random noise code sequence, and a receiver for demodulating and despreading the data-modulated carrier signal, said receiver having a pseudo-random noise code generator, mixer means connected to the pseudo-random noise code generator for mixing the data-modulated carrier signal with a code sequence provided by the pseudo/random noise code generator to despread the carrier signal, and analog indicator means in the receiver for measuring a received signal strength and generating an analog signal; said synchronizer comprising:clock means providing a phase output corresponding to the phase of the clock timer driving the pseudo-random noise code generator in the transmitter,analog to digital conversion means for converting the analog signal to a digital signal indicative of the best correlation between the phase of the transmitted modulated carrier signal and the received modulated carrier signal, anddecoding circuitry connected to the clock means and the analog-to-digital conversion means, including means prior to demodulation of the carrier signal for sampling the analog signal received at each of a plurality of discrete steps in the code sequence, means for determining the peak step when the sampled signal reaches its maximum strength during the code sequence and means for aligning the code sequence of the receiver with the code sequence of the transmitter,wherein the decoding circuitry comprises acquisition state means for determining a peak value in each of the sampled signals during one cycle of the code sequence and for aligning the code sequence of the receiver with the code sequence of the transmitter in response to the peak value, and tracking means for comparing an accumulated peak value over the cycle of the code sequence to a prior accumulated peak value over the cycle of a prior code sequence and shifting the code sequence of the receiver to advance or retard the code sequence of the receiver so as to remain in alignment with the code sequence of the transmitter.