GPS position measuring system and GPS position measuring apparatus

• US 6,329,946 B1
• Filed: 05/31/2000
• Issued: 12/11/2001
• Est. Priority Date: 05/31/2000
• Status: Expired due to Term

• Current Assignee: MiTAC International Corporation (MiTAC Holdings Corp.)
• Original Assignee: Magellan Systems Japan, Inc., Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation), Magellan Corporation (Thales SA)
• Inventors: Hirata, Seiichiro, Lyusin, Sergy V.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US09/584,154
• Time in Patent Office: 559 Days
• Field of Search: 342/357.06, 342/357.12, 342/357.05, 375/150
• US Class Current: 342/357.62
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: G01S 19/254 relating to Doppler shift of satellite signals
• CPC Class Codes: G01S 19/258 relating to the satellite constellation, e.g. almanac, ephemeris data, lists of satellites in view
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 5/0045 Transmission from base station to mobile station G01S5/009 takes precedence

Abstract

A Global Positioning System carries out Doppler correction of a C/A code sequence after a frequency conversion, and calculates a pseudo range by performing correlation calculation between the C/A code, which is obtained by summing up the C/A code sequence beginning from a polarity inversion boundary determined at a correlation peak detecting step ST10, and a C/A code generated in a GPS terminal. When a received electric field detected by a received electric field intensity detector 11 is good, the current position is determined from the pseudo range and the navigation data extracted by the GPS terminal itself, whereas when the received electric field is poor, the current position is determined from the pseudo range and the navigation data sent from an external apparatus.

Claims

1. A Global Positioning System including an external apparatus that receives a GPS signal from a satellite and extracts navigation data and Doppler information from the GPS signal, and a GPS terminal that is connected to the external apparatus through a communication medium and receives the GPS signal from the satellite, said GPS terminal converting a frequency of the GPS signal received;

A/D converting the GPS signal passing through the frequency conversion using a sampling signal consisting of a predetermined number of pulses per unit time;

storing the GPS signal after the A/D conversion for a predetermined time interval;

performing Doppler correction of a carrier frequency of a selected satellite included in the stored GPS signal using local oscillation frequency deviation detection information and Doppler information which is detected by said GPS terminal or provided by said external apparatus;

performing Doppler correction of a C/A code signal of said selected satellite;

performing over a prescribed interval a processing in which corresponding bit values in individual C/A code long blocks of the GPS signal passing through the Doppler correction are multiplied by the navigation data which is provided by the external apparatus or detected by the GPS terminal itself to align polarity of the corresponding bit values, followed by summing up the corresponding bit values over the prescribed interval;

iterating the same processing by a number of the navigation data, followed by obtaining cumulative results of the processings;

carrying out correlation calculation between the cumulative results and the C/A code signal of the selected satellite held in said GPS terminal;

obtaining a delay time to a peak position of the correlation values; and

determining a pseudo range between said GPS terminal and the selected satellite from the delay time.

3. The Global Positioning System according to claim 1, wherein the correlation calculation is terminated when even a very small peak of the correlation calculation values is obtained.

5. The Global Positioning System according to claim 1, wherein the correlation calculation is performed with scanning the navigation data until a maximum peak of the correlation calculation values is obtained.

7. The Global Positioning System according to claim 1, wherein said GPS terminal comprises a GPS radio frequency stage;

a frequency converter;

a local oscillator;

an oscillation frequency deviation detector;

an A/D converter; and

a digital signal processor that includes a memory for storing C/A codes of all satellites and a computing section.

9. The Global Positioning System according to claim 7, wherein said oscillation frequency deviation detector comprises a memory for storing data used for estimating frequency drifts for temperatures, and uses, as Doppler correction data, data read from said memory in response to a temperature detected by a temperature sensor for detecting temperature of said local oscillator.

10. The Global Positioning System according to claim 9, wherein said GPS terminal sets a scanning start position of Doppler correction of the navigation data in accordance with a sum of the Doppler correction data read from said memory in response to the temperature detected by said temperature sensor for detecting the temperature of said local oscillator and the Doppler information one of said external apparatus and GPS terminal provides.

11. The Global Positioning System according to claim 7, wherein said GPS terminal receives from an external apparatus a reference signal with higher accuracy than that generated by a reference oscillator installed in said GPS terminal, detects the local oscillation frequency deviation by counting the oscillation frequency over an interval of the reference signal with the higher accuracy;

and uses detected data as the Doppler correction data.

12. The Global Positioning System according to claim 10, wherein said GPS terminal detects the local oscillation frequency deviation by counting the oscillation frequency over an interval of a reference signal sent from an external apparatus;

and sets the scanning start position of the Doppler correction of the navigation data in response to a sum of Doppler correction data corresponding to the detected local oscillation frequency deviation and the Doppler information one of said external apparatus and GPS terminal itself provides.

13. The Global Positioning System according to claim 1, wherein said local oscillator comprises a reference oscillator, and stabilizes an oscillation frequency of said reference oscillator in synchronism with a frequency supplied from an external apparatus with higher accuracy than the oscillation frequency of said reference oscillator.

14. The Global Positioning System according to claim 1, wherein said GPS terminal iterates, when the peak position of the correlation calculation values is not obtained, the scanning of the navigation data until the peak position of the correlation calculation values is obtained with varying at least one of Doppler correction data from an oscillation frequency deviation detector and the Doppler information which is provided by said external apparatus or detected by said GPS terminal.

15. The Global Positioning System according to claim 13, wherein scanning of the navigation data utilizes a binary scanning method.

16. The Global Positioning System according to claim 1, wherein said GPS terminal generates I signal data and Q signal data with their carrier components removed by multiplying the GPS signal read from said memory by GPS carrier sine data and GPS carrier cosine data which are orthogonal to each other and pass through the frequency conversion;

multiplies the I signal data and Q signal data by sine data and cosine data of a frequency shift obtained by summing Doppler correction data fed from an oscillator frequency deviation detector and the Doppler data which is provided by said external apparatus or detected by said GPS terminal itself;

extracts from resultant signals C/A code signals which are Doppler corrected and orthogonal to each other; and

carries out correlation calculation of I and Q signals of the C/A code signals, followed by vector composition.

18. The Global Positioning System according to claim 1, wherein the prescribed number can be increased of the sampling signal for the A/D conversion which is carried out after the frequency conversion of the received GPS signal.

19. The Global Positioning System according to claim 1, wherein said GPS terminal transmits its time signal to a time server that generates an exact time signal, and receives the time signal from the time server to know a traveling time of a signal from said GPS terminal to said server.

20. The Global Positioning System according to claim 1, wherein said external apparatus comprises a time server generating an exact time signal, and wherein said GPS terminal transmits its time signal to said time server that generates the exact time signal, receives the time signal from the time server to know a traveling time of a signal from said GPS terminal to said server, and sets a scanning start position for multiplying the GPS signal by the navigation data in response to the traveling time.

21. The Global Positioning System according to claim 20, wherein the scanning of the navigation data utilizes a binary scanning method.

22. The Global Positioning System according to claim 1, wherein the correlation calculation interval is made variable in response to an electric field intensity detected by a received electric field intensity detector for detecting a condition of the received electric field.

23. The Global Positioning System according to claim 1, wherein the summing up interval is made variable in response to a condition of a received electric field.

2. A Global Positioning System including an external apparatus that receives a GPS signal from a satellite and extracts navigation data and Doppler information from the GPS signal, and a GPS terminal that is connected to the external apparatus through a communication medium and receives the GPS signal from the satellite, said GPS terminal converting a frequency of the GPS signal received;

A/D converting the GPS signal passing through the frequency conversion using a sampling signal consisting of a predetermined number of pulses per unit time;

storing the GPS signal after the A/D conversion for a predetermined time interval;

performing Doppler correction of a carrier frequency of a selected satellite included in the stored GPS signal using local oscillation frequency deviation detection information and Doppler information one of said GPS terminal and said external apparatus provides;

performing Doppler correction of a C/A code signal of said selected satellite;

performing over a prescribed interval a processing in which corresponding bit values in individual C/A code long blocks of the GPS signal passing through the Doppler correction are multiplied by the navigation data one of the external apparatus and the GPS terminal provides to align polarity of the corresponding bit values, followed by summing up the corresponding bit values over the prescribed interval, and by an averaging processing of the sums;

carrying out correlation calculation between the averaging results and the C/A code held in said GPS terminal;

iterating similar correlation calculations sequentially for the GPS signal stored in said memory over the prescribed interval;

scanning, when a peak of the correlation calculation values is not obtained, the navigation data by a length of an integer multiple of the C/A code length;

obtaining a delay time to a peak position of the correlation values; and

determining a pseudo range between said GPS terminal and the selected satellite from the delay time.

4. The Global Positioning System according to claim 2, wherein the correlation calculation is terminated when even a very small peak of the correlation calculation values is obtained.

6. The Global Positioning System according to claim 2, wherein the correlation calculation is performed with scanning the navigation data until a maximum peak of the correlation calculation values is obtained.

8. The Global Positioning System according to claim 2, wherein said GPS terminal comprises a GPS radio frequency stage;

a frequency converter;

a local oscillator;

an oscillation frequency deviation detector;

an A/D converter; and

a digital signal processor that includes a memory for storing C/A codes of all satellites and a computing section.

17. The Global Positioning System according to claim 2, wherein said GPS terminal generates I signal data and Q signal data with their carrier components removed by multiplying the GPS signal read from said memory by GPS carrier sine data and GPS carrier cosine data which are orthogonal to each other and pass through the frequency conversion;

multiplies the I signal data and Q signal data by sine data and cosine data of a frequency shift obtained by summing Doppler correction data fed from an oscillator frequency deviation detector and the Doppler data which is provided by said external apparatus or detected by said GPS terminal itself;

extracts from resultant signals C/A code signals which are Doppler corrected and orthogonal to each other; and

carries out correlation calculation of I and Q signals of the C/A code signals, followed by vector composition.

24. A Global Positioning apparatus including an external apparatus that receives a GPS signal from a satellite and extracts navigation data and Doppler information from the GPS signal, and a GPS terminal that is connected to the external apparatus through a communication medium and receives the GPS signal from the satellite, said GPS terminal comprising:

storing means for storing for a predetermined time interval the received GPS signal that passes through a frequency conversion and an A/D conversion using a sampling signal consisting of a predetermined number of pulses per unit time;

dividing means for dividing the GPS signal stored in said storing means by navigation data which is detected by said GPS terminal itself or provided by said external apparatus;

sum-up means for performing over a prescribed interval a processing in which the divided GPS signal are multiplied by the navigation data to align polarity, followed by summing up over the prescribed interval;

iterating means for iterating similar processing by a number of the navigation data to obtain cumulative results;

correlation calculation means for carrying out correlation calculation between the cumulative sums and the C/A code sequence of a selected satellite held in said GPS terminal, and for obtaining a delay time to a peak position of the correlation values; and

pseudo range detecting means for determining a pseudo range between said GPS terminal and the selected satellite from the delay time to the peak position.