JP3543665B2 - GPS receiving terminal with communication function - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a GPS (Global Positioning System) receiving terminal having communication means such as a mobile phone, a satellite mobile phone, and a PHS.
[0002]
[Prior art]
FIG. 5 shows a schematic configuration of a GPS receiving terminal with a communication function. In the figure, SV1 to SV3 are GPS visible satellites, and information such as satellite numbers and Doppler frequencies are obtained from signals received by the base station 30 via the GPS antenna 31 and transmitted to the GPS receiving terminal 10 via the communication means 22 and 21. Will be informed. The GPS receiving terminal 10 performs only frequency synchronization and phase synchronization processing for capturing and tracking a signal from a visible satellite received by the GPS antenna 11, and transmits data necessary for calculating its own current position to a communication unit. It is sent to the base station 30 via 21 and 22. The base station 30 calculates the position and the like of the GPS receiving terminal 10 based on the data sent from the GPS receiving terminal 10. In order to improve the accuracy of the position calculation, the base station 30 may use DGPS correction information received from the FM broadcast receiving antenna 32 or the like. The calculated location information of the terminal 10 is used by the base station 30 or, depending on the application, transmitted to the GPS receiving terminal 10 via the communication means 22 and 21.
[0003]
[Problems to be solved by the invention]
This GPS receiving terminal with a communication function is used for a personal navigation system, a search for a wandering elderly person, a position detection system for crime prevention, and the like. It is desired that the power consumption of the battery be reduced in order to enable the above.
[0004]
In the GPS receiving terminal with a communication function, as described above, it is not necessary to perform the operation to determine the position in the terminal body, but to perform the operation to determine the position in the base station. Further, since information relating to GPS visible satellites is also provided from the base station, unlike a GPS receiver incorporated in a car navigation system, it is not necessary to perform a search process for knowing the satellite number of a visible satellite. For this reason, compared to a GPS receiving terminal without a communication function, the required circuits are smaller and the time required for positioning can be reduced.
[0005]
However, since it has a communication function, when the GPS reception function and the communication function are used at the same time, power consumption increases. Further, if a plurality of correlators are simultaneously operated in order to speed up a correlation operation for achieving phase synchronization, power consumption further increases. Further, if the correlation operation is speeded up, the possibility of erroneous satellite lock increases.
[0006]
The present invention has been made in view of such circumstances, and it is an object of a GPS receiving terminal with a communication function to obtain a maximum calculation speed with a circuit as small as possible without increasing power consumption.
[0007]
[Means for Solving the Problems]
The GPS receiving terminal with a communication function according to the present invention is based on a method in which a signal output from a GPS receiving unit is temporarily stored in a memory and is used repeatedly several times. By devising it, it is possible to obtain the maximum efficiency with the minimum circuit configuration.
[0008]
Specifically, according to the first aspect of the present invention, a GPS antenna 11, a GPS receiving unit (RF front-end unit 12) that converts the frequency of a GPS signal received by the GPS antenna 11, and a signal output from the GPS receiving unit A memory 13 for storing a signal read from the memory 13, a switch 14 for switching between a signal read from the memory 13 and a signal output from the GPS receiver, and a switch 14 for outputting a signal read from the memory 13 from the switch 14. Is a control circuit 19 for shutting off the power supply to the GPS receiver, a communication means 21 for exchanging signals with a base station 30 having an arithmetic function of a terminal position and the like, and a visible satellite transmitted from the base station 30 by the communication means 21. A pseudo-noise code signal generator 18 for generating a pseudo-noise code signal for capturing a visible satellite based on information at a plurality of different phases; A plurality of correlators 16 for obtaining a correlation between a signal output from the CDMA and a pseudo-noise code signal, and a plurality of automatic tracking units 17 for outputting data for position calculation to be transmitted to the base station 30 via the communication means 21. It is characterized by having.
[0009]
Here, the automatic tracking unit 17 has a smaller number than the correlator 16, inputs a plurality of pseudo-noise code signals having the same frequency and shifted phases to the plurality of correlators 16, respectively. By calculating the correlation, a plurality of correlations having different phases are simultaneously generated with respect to the pseudo-noise code signal of the same satellite number, and the phase at which the carrier correlation value becomes a peak is used for phase synchronization of one automatic tracking unit. The time required to establish synchronization can be reduced. Further, by calculating the sum of a plurality of carrier correlation values near the peak and comparing the sum with a predetermined threshold, a steep peak can be excluded as an erroneous satellite lock. Further, the process of sampling the signal from the GPS receiving unit a plurality of times during 1 ms, which is the code length of the C / A code, and accumulating the signal in the memory is continued for a predetermined time. The carrier-to-noise ratio can be increased by inputting the correlated data by shifting the time axis every 1 ms and superimposing data on the data corresponding to an integral multiple of the length of 1 ms.
[0010]
Further, the calculation time can be further reduced by diverting the offset unique to the circuit obtained when the first satellite is captured and tracked during the capture and tracking of the second and subsequent satellites. After capturing and tracking the first satellite, when capturing and tracking the second and subsequent satellites, a specific chip (for example, the first chip) of the pseudo noise code of the first satellite and the second A difference in time for receiving the same chip of the pseudo noise code of the third and subsequent satellites may be calculated for each chip number and transmitted to the base station. In addition, when accumulating the signal from the GPS receiver in the memory, the amount of accumulation is variable, so that the positioning time can be shortened when the reception condition is good.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
(Example 1)
FIG. 1 is a block diagram showing an example of the configuration of the GPS receiving terminal 10 according to the first embodiment. In the figure, reference numeral 11 denotes a GPS antenna, and reference numeral 12 denotes an RF front end unit serving as a GPS receiving unit, which receives a 1.57542 GHz high frequency from a GPS satellite, converts the frequency, and outputs a digital signal of about several MHz. Reference numeral 13 denotes a memory that stores digital signals output from the RF front-end unit 12 over a predetermined time. Reference numeral 14 denotes a switch for selecting whether to send the data output from the RF front-end unit 12 to the correlator 16 as it is, or to send the data read from the data once stored in the memory 13 to the correlator 16. . Reference numeral 15 denotes an adder, which is used in Example 4 to improve the carrier-to-noise ratio by adding data every 1 ms. Reference numeral 16 denotes a correlator, which operates n (n is an integer of 3 or more) correlators at the same time so that phase synchronization can be quickly established. That is, the pseudo-noise code signal generator 18 generates a pseudo-noise code of the number of the visible satellite, and generates n pseudo-noise code signals whose phases are slightly shifted from the first to n-th. To the correlator 16, and takes a correlation with the signal output from the switch 14. This makes it possible to find the phase at which the carrier correlation value has a peak in a short time. Reference numeral 17 denotes an automatic tracking unit, which locks signals from different visible satellites by m (m is an integer of 3 or more and n> m) automatic tracking units, and transmits the signals via the communication units 21 and 22 of FIG. To the base station 30. The base station 30 analyzes signals from three or more satellites and calculates the position of the GPS receiving terminal 10. The base station 30 notifies the GPS receiving terminal 10 of information on visible satellites via the communication means 22 and 21 in advance. Accordingly, the GPS receiving terminal does not need to search for the number of the visible satellite, and the plurality of correlators 16 start from the processing for achieving phase synchronization with the pseudo noise code of the satellite number notified from the base station 10. And the time required for positioning can be reduced. Further, the control circuit 19 controls the operation of each unit, and stops the operation of the RF front-end unit 12 during the period of reading data from the memory 13 to the correlator 16, thereby reducing power consumption. .
[0012]
In the present embodiment, (n−m + 1) correlators 16 share one automatic tracking unit 17. When the numbers of the correlators 16 and the automatic tracking units 17 are different from each other, a plurality of correlators are assigned to one automatic tracking unit. In general, the number of visible tracking satellites is sufficient for the automatic tracking unit, so that the number is often smaller than the number of correlators. In addition, the circuit-specific offset (that is, the difference between the pseudo-noise code from the satellite and the pseudo-noise code of the receiver) obtained when the first satellite is acquired and tracked is determined by the acquisition of the second and subsequent satellites. -By diverting during tracking, it is possible to easily capture and track the second and subsequent satellites. After capturing and tracking the first satellite, when capturing and tracking the second and subsequent satellites, a specific chip (for example, the first chip) of the pseudo noise code of the first satellite is used. The difference between the times at which the same chip of the second and subsequent satellites receives the same chip may be calculated in units of chips and transmitted to the base station.
[0013]
(Example 2)
FIG. 2 is an explanatory diagram of the second aspect. The curve in the figure shows the curve of the carrier correlation value. The horizontal axis of the graph is the phase shift, the vertical axis is the carrier correlation value, and the point x plotted on the graph is the carrier correlation value obtained by the first to n-th correlators at a certain time. is there. As described above, since a plurality of carrier correlation values are obtained simultaneously by a plurality of correlators, a phase at which the carrier correlation value has a peak can be obtained in a short time. Also, instead of operating the GPS receiver and the correlator simultaneously, when the GPS receiver is operating, the operation of the correlator is stopped, the received data is temporarily stored in the memory, and the data is stored from the memory. In the reading period, the peak of the power consumption can be reduced by stopping the operation of the GPS receiving unit and starting the operation of the correlator. Furthermore, by making the speed of reading data from the memory faster than the speed of storing data in the memory, the speed of the correlation operation in the correlator can be increased, and the data from the GPS receiver is directly used. Compared with the case, the time required to capture all visible satellites can be reduced, and the total power consumption can be reduced accordingly.
[0014]
(Example 3)
FIG. 3 is an explanatory diagram of claim 3. Two curves in the drawing show curves of the carrier correlation value. The horizontal axis of the graph is the phase shift, the vertical axis is the carrier correlation value, and the point x plotted on the graph is the carrier correlation value obtained by the first to n-th correlators at a certain time. is there. The curve on the left is a curve of a carrier correlation value of a desired satellite (SV1), and the curve on the right is a curve of a carrier correlation value of another satellite (SV2) other than the desired satellite. When there is an obstruction between the desired satellite SV1 and the receiver and the receiving condition is poor, and there is little obstruction between the other satellite SV2 which is not the desired satellite and the receiver, the signal received from each satellite is thus obtained. The intensity may be approximately equal. In such a case, it is necessary to set a low threshold value represented by a broken line, and if the correlation value is only one point, the correlation of another satellite that is not the desired satellite is also the same as the correlation of the desired satellite. It can be mistaken. However, since the curve of the correlation value of another satellite that is not the desired satellite is generally steeper than the curve of the correlation value of the desired satellite, the sum of the correlation values represented by x is calculated, and the sum is used as a criterion. Accordingly, when the correlation is determined based on only one correlation value, it is possible to avoid occurrence of erroneous satellite lock in which the correlation value of another satellite other than the desired satellite is mistaken for the correlation value of the desired satellite.
[0015]
(Example 4)
FIG. 4 is an explanatory diagram of claim 4. In this example, when data output from the GPS receiving unit is stored in the memory, sampling is performed 2048 times per 1 ms, the time axis is shifted every 1 ms, and the data is overlapped by 3 ms, and another address of the memory is stored. In the example shown in FIG. Here, 1 ms corresponds to the code length of the C / A code that is open to the public among the pseudo noise codes (PN codes). When the data stored at the different address is read from the memory and sent to the correlator, the superimposed data also appears to the correlator as if sampling was performed 2048 times in 1 ms. The ratio is improved. This is because the carrier component has a correlation every 1 ms, which is the code length of the C / A code, but the noise component has a Gaussian distribution, and when superimposed, the increase rate of the carrier component exceeds the increase rate of the noise component. is there. As a result, with a simple circuit configuration, it is possible to increase the carrier-to-noise ratio and minimize the influence of noise components. In the case of performing a process of superimposing data in the memory by shifting the time axis as in this embodiment, a large amount of data to be stored in the memory is required. By omitting the above processing, the amount of data stored in the memory can be reduced and the processing can be speeded up.
[0016]
In the present embodiment, an example has been described in which data superimposed by shifting the time axis is stored at another address of the memory 13. However, as shown in the configuration of FIG. In the case where the adder 15 is arranged, the data of 3 ms in FIG. 4A is read out from the memory 13 in a short time within 1 ms and stored in the buffer of the adder 15, and as shown in FIG. The data after the addition by shifting the time axis may be output from the adder 15 to the correlator 16 at a rate of 2048 samples per ms. In this case, the capacity of the memory 13 can be reduced.
[0017]
【The invention's effect】
According to the first aspect of the present invention, it is possible to perform high-speed operation by temporarily storing a signal from the GPS receiving unit in the memory, and there is a problem of erroneous locking which is usually in a trade-off relation with high-speed operation. Can also be avoided. In addition, since the power supply to the GPS receiving unit can be cut off during a period in which a signal is being read from the memory, power consumption can be reduced and the circuit scale can be reduced.
[0018]
According to the second aspect of the present invention, a plurality of pseudo-noise code signals having the same frequency and shifted in phase are input to a plurality of correlators, and a correlation with a signal output from a switch is obtained, thereby obtaining the same satellite. By simultaneously generating a plurality of correlations having different phases with respect to the pseudo-noise code signal of the number, the peak of the carrier correlation value can be calculated at high speed.
According to the third aspect of the present invention, the sum of the plurality of carrier correlation values near the peak is obtained and compared with a predetermined threshold value. Can be prevented from being locked to the signal.
[0019]
According to the fourth aspect of the present invention, the process of sampling the signal from the GPS receiving unit a plurality of times during 1 ms which is the code length of the C / A code and storing it in the memory is continued for a predetermined time, and the sampling start time , The carrier-to-noise ratio can be reduced by inputting data obtained by superimposing the data corresponding to an integer multiple of 1 ms which is the code length of the C / A code by shifting the time axis every 1 ms to the correlator. The difference can be sensed between the Doppler frequency from the base station and the actual Doppler frequency.
[0020]
According to the fifth aspect of the present invention, the offset unique to the circuit obtained when the first satellite is captured and tracked is used at the time of capturing and tracking the second and subsequent satellites. The time required for satellite acquisition and tracking can be reduced.
According to the invention of claim 6, after capturing and tracking the first satellite, when capturing and tracking the second and subsequent satellites, a specific chip of the pseudo noise code of the first satellite and 2 The difference between the times of receiving the same chip of the pseudo-noise code of the second and subsequent satellites is calculated per chip number and transmitted to the base station, so the time required for acquisition and tracking of the second and subsequent satellites is reduced. Can be shortened.
According to the invention of claim 7, when the signal from the GPS receiving unit is stored in the memory, the amount of storage is variable, so that the correlation can be obtained at high speed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a GPS receiving terminal with a communication function of the present invention.
FIG. 2 is an explanatory diagram of the invention of claim 2;
FIG. 3 is an explanatory view of the invention of claim 3;
FIG. 4 is an explanatory view of the invention of claim 4;
FIG. 5 is an explanatory diagram showing a usage state of a conventional GPS receiving terminal with a communication function.
[Explanation of symbols]
Reference Signs List 10 GPS receiving terminal 11 GPS antenna 12 RF front end unit 13 Memory 14 Switcher 15 Adder 16 Correlator 17 Automatic tracking unit 18 Pseudo noise code generator 19 Control circuit 21 Communication means (GPS receiving terminal side)
22 Communication means (base station side)
30 base stations

Claims (7)

A GPS antenna, a GPS receiver for frequency-converting a GPS signal received by the GPS antenna, a memory for storing a signal output from the GPS receiver, a signal read from the memory and a signal output from the GPS receiver. Signals are exchanged between a switch for switching, a control circuit for shutting off power supply to a GPS receiving unit during a period in which a signal read from a memory is output from the switch, and a base station having an arithmetic function for a terminal position and the like. Communication means, a pseudo-noise code signal generator for generating a pseudo-noise code signal for capturing a visible satellite at a plurality of different phases based on information on the visible satellite notified from the base station by the communication means, and a switch. And a plurality of correlators for obtaining a correlation between the signal output from the base station and the pseudo-noise code signal, and data for calculating the position to be transmitted to the base station via the communication means. GPS receiving terminal with a communication function, characterized in that it comprises a plurality of automatic tracking unit for outputting. In claim 1, the number of auto-tracking units is smaller than the number of correlators, a plurality of pseudo-noise code signals having the same frequency and shifted in phase are input to a plurality of correlators, and the correlation with the signal output from the switch is determined. A plurality of correlations having different phases are simultaneously generated with respect to the pseudo-noise code signals having the same satellite number, and a phase having a peak carrier correlation value is used for phase synchronization of one automatic tracking unit. GPS receiver with function. 3. The GPS receiving terminal with a communication function according to claim 2, wherein a sum of a plurality of carrier correlation values near the peak is compared with a predetermined threshold. 2. The method according to claim 1, wherein the process of sampling the signal from the GPS receiving unit a plurality of times during 1 ms, which is the code length of the C / A code, and accumulating the signal in the memory is continued for a predetermined period of time. A GPS receiving terminal with a communication function, characterized in that, for data corresponding to an integral multiple of 1 ms, which is the code length of the code, data obtained by superimposing the data by shifting the time axis every 1 ms is input to the correlator. 2. The GPS receiving terminal with a communication function according to claim 1, wherein an offset unique to a circuit obtained when the first satellite is captured and tracked is used when capturing and tracking the second and subsequent satellites. 2. The method according to claim 1, wherein after capturing and tracking the first satellite, when capturing and tracking the second and subsequent satellites, a specific chip of the pseudo noise code of the first satellite and the second and subsequent satellites are used. A GPS receiving terminal with a communication function, which calculates a difference in time for receiving the same chip with a pseudo noise code of a satellite in units of the number of chips and transmits the result to a base station. 2. The GPS receiving terminal with a communication function according to claim 1, wherein when the signal from the GPS receiving unit is stored in the memory, the amount of storage is variable.

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