GPS position measuring method and GPS position measuring system

• US 20050116860A1
• Filed: 09/03/2004
• Published: 06/02/2005
• Est. Priority Date: 12/01/2003
• Status: Active Grant

• Current Assignee: Magellan Systems Japan, Inc.
• Original Assignee: Magellan Systems Japan, Inc.
• Inventors: Kishimoto, Nobuhiro, Hirata, Seiichiro
• Granted Patent: US 7,408,504 B2
• Time in Patent Office: Days
• US Class Current: 342/357.630
• CPC Class Codes: G01S 19/24 Acquisition or tracking or demodulation of signals transmitted by the system synchronisation aspects of direct sequence spread spectrum modulation H04B1/7073
• CPC Class Codes: G01S 19/246 involving long acquisition integration times, extended snapshots of signals or methods specifically directed towards weak signal acquisition

Abstract

A GPS positioning method to obtain pseudorange between a receiver terminal and a satellite by capturing a portion of received satellite signals of a predetermined time duration. A predetermined number of first input signals, equivalent to 1-bit of navigation data, are obtained with various delays in the starting point of processing. The first input signals are synchronously summed up to obtain second input signals. A PN code replica (pseudopattern) prepared by the receiver terminal operates on the second input signals to detect the polarity of the navigation bits and correct the polarity of the bits so that the bit polarity of the second input signals are always positive. Synchronous summation is conducted on the resulting signals, which have been derived from the complete captured signal, and a correlation calculation is conducted on the obtained synchronously summed signal using a replica PN code prepared by the receiver terminal, the signal delay value is detected and pseudorange is obtained using the result of the correlation calculation.

Claims

1. A GPS position measuring method in which a receiver terminal receives a signal from a satellite and calculates pseudorange between the satellite and the receiver terminal by capturing a portion of the received satellite signal having predetermined time duration, comprising the steps of:

obtaining a predetermined number of first input signals, each having a length equivalent to one bit of navigation data, from the received satellite signal of predetermined time duration, and using a plurality of delays of the beginning of data processing with spacing of the delays being small relative to the duration of a navigation data bit;

synchronous summation of the first input signals to make second input signals;

a polarity modifying calculation process in which a pseudo pattern prepared by the receiver terminal is applied to the second input signals to homogenize the polarity of the navigation data bits;

synchronous summation of the signals obtained by the polarity modifying calculation process from the received satellite signals having predetermined time duration;

correlation calculation of the obtained synchronous summation signals and a replica PN code prepared by the receiver terminal;

detecting the signal delay value by using the results of the correlation calculation; and

calculating the pseudorange by using the delay value.

3. The GPS position measuring method as set forth in claim 1, wherein the pseudopattern in the polarity modifying calculation process is a data column of a predetermined bit number equivalent to a unit frame of the signal from the satellite, and composed of groups of the data columns of the same number as the predetermined bit number serially changed for one bit respectively.

2. A GPS position measuring method in which a receiver terminal receives a signal from a satellite and calculates pseudorange between the satellite and the receiver terminal by capturing a portion of the received satellite signal having predetermined time duration, comprising the steps of:

an early signal process, in which a predetermined number of first input signals, each having a length of 20 msec, are obtained from the received satellite signal of predetermined time duration, and using a plurality of delays of the beginning of data processing with spacing of delays being small compared to the length of a navigation data bit, conducted on the received satellite signal of predetermined time duration;

synchronous summation of the first input signals to make second input signals;

a polarity modifying calculation process in which result of multiplication or division and average calculation of the second input signals by a pseudopattern prepared by the receiver terminal multiplies the second input signals further;

synchronous summation of the signals obtained by the polarity modifying calculation process;

correlation calculation of said synchronously summed signals and a replica PN code prepared by the receiver terminal;

detecting the delay value using the results of the correlation calculation; and

calculating the pseudo range using the delay value.

6. The GPS position measuring method as set forth in claim 2, wherein the pseudopattern in the polarity modifying calculation process is a data column of a predetermined bit number equivalent to a unit frame of the signal from the satellite, and composed of groups of the data columns of the same number as the predetermined bit number serially changed for one bit respectively.

4. A GPS position measuring system in which a receiver terminal receives a signal from a satellite and calculates pseudorange between the satellite and the receiver terminal using the received satellite signal of predetermined time duration, comprising a receiver terminal provided with;

a first calculation block portion to obtain a predetermined number of first input signals, each having a length equivalent to one bit of navigation data, from the received satellite signal of predetermined time duration, and using a plurality of delays of the beginning of data processing with the spacing of delays being small compared to the length of a navigation data bit;

a second calculation block portion to synchronously sum up the first input signals to make a second input signal;

a polarity modifying calculation block portion in which the result of multiplication or division and average calculation of the second input signals by a pseudopattern prepared by the receiver terminal multiplies the second input signals further;

a synchronous summation block portion to conduct synchronous summation of the signals obtained by the polarity modifying calculation block portion from the received satellite signal having predetermined time duration;

a correlation calculation block portion to conduct correlation calculation of the obtained synchronous summation signals and a replica PN code prepared by the receiver terminal; and

a pseudo range detecting block portion to detect delay value using the results of the correlation calculation and calculate the pseudorange using the delay value.

5. The GPS position measuring system as set forth in claim 4, wherein the polarity modifying calculation block portion has a multiplying-dividing portion to multiply or divide the second input signal with the pseudo pattern prepared by the receiver terminal, an average calculation portion to average the result by the multiplying-dividing portion, and a polarity modifying calculation portion to multiply the second input signal by the result of the average calculation portion.