Patent ID: 6297770
Filing Date: 2001-10-02
Classification: G01S

Abstract:
A Global Positioning System (GPS) including an external system that receives a GPS signal from a satellite and extracts navigation data and Doppler information from the GPS signal, and a GPS terminal connected to the external system through a communication medium and receiving the GPS signal from the satellite, wherein each bit of the navigation data includes a plurality of PN frames, each frame including many chips arranged in a pattern, said GPS terminal comprising:a frequency converter for converting frequency of the GPS signal received by the GPS terminal;an analog-to-digital (A/D) converter for converting the GPS signal passing through the frequency converter into corresponding GPS data;a memory for storing the GPS data as stored GPS data for a time interval;a Doppler correction section for Doppler correction of the stored GPS data to produce Doppler corrected data, using Doppler information from one of the GPS terminal and the external system;means for sequentially dividing the Doppler corrected data into a plurality of data blocks with a length of a navigation data bit in accordance with navigation data supplied from one of the GPS terminal and the external system;means for calculating, for each of the data blocks, a cumulative sum of chips for corresponding positions in individual PN frames in the data block;means for multiplying each cumulative sum by a corresponding navigation data bit and for outputting a plurality of products of the cumulative sums and the navigation data bits;means for summing the plurality of products for respective chip positions; andmeans for computing correlation between a set of sums of the products and a PN code sequence generated in the GPS terminal, and for calculating a pseudo range between the GPS terminal and the satellite from a correlation peak at a maximum correlation.