JPH11326487A - Gps receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize an access at a short time which is not restricted by a temperature condition by accumulating a temperature characteristic information and using it without previously measuring and storing a characteristic variation of TCXO (temperature compensation quartz generator). SOLUTION: A GPS receiver 1 is provided with an antenna 2 receiving an electric wave transmitted from a satellite; a high-frequency amplification circuit 3 amplifying the electric wave received by the antenna 2; a frequency conversion circuit 4 converting an output signal of the amplification circuit 3 to an intermediate frequency signal; an A/D conversion circuit 5 digital-converting the intermediate frequency signal outputted from the frequency conversion circuit 4; a digital processing circuit 6 getting back a digital signal converted by the converter 5; a synthesizer 7 transmitting a clock signal to the respective portions; TCXO 8 operating the synthesizer 7; and a temperature sensor 9 disposed at the neighborhood to the TCXO 8.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS receiver and, more particularly, to a technology for improving a temperature compensation function of a reference oscillator for supplying a high frequency signal for frequency conversion to a signal processing circuit.

[0002]

2. Description of the Related Art GPS receivers usually provide a tracking system to enable more accurate positioning of the current position. The band width of the loop is narrowed to receive radio signals from artificial satellites.

By the way, immediately after the GPS receiver is turned on, the transmission frequency changes rapidly due to the temperature characteristic of the transmission frequency of a temperature compensated crystal oscillator (hereinafter referred to as TCXO) as a reference signal generating means. If you want to supplement the radio wave of the above, first, during the period until the transmission frequency of TCXO is stabilized, the range of the frequency to search for the signal is expanded and received, and the orbit data is demodulated from the obtained measured value. , It was necessary to measure the distance and perform accurate positioning of the current position.

[0004] However, in such a method, the time required to execute an accurate positioning operation is considerably long.

To reduce the time from power-on to measurement, Japanese Patent Laid-Open No.
Japanese Patent Application Publication No. 08587 discloses an example. According to the invention described in this publication, the temperature characteristic of the transmission frequency of the receiving TCXO is stored in a readable storage means, and a temperature sensor is disposed near the TCXO,
When turning on the power of the GPS receiver, the TCXO stored in the storage means based on the temperature information derived from the temperature sensor.
By reading the predicted frequency related to the temperature characteristic of the above, the time from when the power is turned on to when the GPS satellite signal is captured is shortened.

However, such a temperature compensation means for TCXO has the following technical problems.

[0007]

That is, the deviation between the output of the temperature sensor and the output frequency of the TCXO is not a simple relationship. To determine the output frequency of the TCXO from the output of the temperature sensor, It is necessary to divide the output of TCXO in an appropriate range, and to store in advance the deviation amount of the output frequency of TCXO within this range. To this end, the temperature fluctuation of TCXO is measured in advance, There is a disadvantage that an operation for storing the information in a storage means such as a ROM table is required, and an extra production cost is required.

Further, in the case of the temperature compensating means disclosed in the above-mentioned publication, it is not possible to compensate for the drift amount outside the previously measured temperature range. For example, there were restrictions on use in cold and extremely hot regions. The present invention has been made in view of such a conventional problem, and an object of the present invention is to accumulate temperature characteristic information with use without measuring and storing the characteristic fluctuation of TCXO in advance. Another object of the present invention is to provide a GPS receiver which can be accessed in a short time without being restricted by temperature conditions.

[0009]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides an antenna for receiving radio waves transmitted from an artificial satellite, and a digital signal transmitted from a plurality of artificial satellites received via the antenna. And convert to
GPS equipped with a signal processing circuit for obtaining coordinate values on the earth
In the receiver, a reference oscillator that supplies a high-frequency signal for frequency conversion to the signal processing circuit, a temperature sensor disposed near the reference oscillator, and a storage that stores frequency characteristic information corresponding to the temperature of the reference oscillator. Means, comparing the storage content of the storage means and the detected value of the temperature sensor, determining the presence or absence of frequency characteristic information corresponding to the detected value and the presence or absence of approximate frequency characteristic information of the detected value, When it is determined that the frequency characteristic information is present in the determination unit, a high-speed positioning mode to narrow the search range of the received radio wave is executed, when the determination unit determines that there is the approximate frequency characteristic information, The high-speed positioning mode is executed after calculating the virtual frequency characteristics by the interpolation method, and when the determination means determines that there is no approximate frequency characteristic information, the reception power A switching command means to perform the positioning mode to the search range and wide band, when it is determined that there is the approximate frequency information in the determination unit, and,
When it is determined that there is no approximate frequency characteristic information, after positioning is completed, based on the Doppler amount calculated in each of the positioning modes, calculating means for calculating a frequency of the reference oscillator corresponding to a corresponding temperature, and the calculating means And a writing means for writing the result of the calculation in the storage means. According to the GPS receiver configured as described above, in the initial state of the GPS receiver, if there is no frequency characteristic information, or if there is only limited frequency characteristic information that is initially set, the entire band is subjected to frequency search. In many cases, the frequency characteristic information is executed in the positioning mode in which
Since the information is sequentially added to the storage means, the accuracy of the frequency measurement information is increased by repeating the measurement. When the frequency of use is increased, the positioning can be performed in a shorter time. If there is no corresponding frequency characteristic information, the frequency characteristic corresponding to the temperature is virtually determined from the frequency characteristic information corresponding to the temperature already stored in the storage means, so that positioning in a short time can be performed. Becomes possible.

[0010]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG.
Shows an embodiment of the GPS receiver according to the present invention. The GPS receiver 1 shown in FIG. 1 includes an antenna 2 for receiving a radio wave transmitted from a satellite, a high-frequency amplifier circuit 3 for amplifying the radio wave received by the antenna 2, and an output signal of the amplifier circuit 3 as an intermediate frequency signal. A frequency conversion circuit 4 for conversion, an A / D conversion circuit 5 for digitally converting an intermediate frequency signal output from the frequency conversion circuit 4, a digital processing circuit 6 for demodulating the digital signal converted by the converter 5, It includes a synthesizer 7 for sending a clock signal to each section, a TCXO 8 for operating the synthesizer 7, a temperature sensor 9 arranged near the TCXO 8, and the like.

An output terminal of the A / D conversion circuit 5 is connected to a PN signal generator 12 and an NCO 1 through mixers 10 and 11.
3, connected to the I / O port 15 of the computer for control and operation through the LPF 14 and sends out a detection signal to the computer through the LPF 14 and is operated by a search control signal and a control signal from the computer. It has become so.

Further, the positioning data demodulated by the digital processing circuit 6 and the measured value of the temperature sensor 9 are also taken into the computer, and the result of the arithmetic processing is output to a display (not shown).

The computer has a CPU 16 and a ROM 1
7, a RAM 19 for storing almanac data, a RAM 20 for storing a temperature drift table, and a backup power supply 21 for the RAMs 19 and 20 in addition to a general configuration such as a RAM 18.

The RAMs 19 and 20 thus configured are:
Even in the power-off state, since the power is backed up by the power supply 21, the written contents are always retained, and the stored contents can be used next time.

It is needless to say that a read / write rewritable flash PROM which does not lose data even in the power-off state can be used in place of such a backup-held RAM.

The CPU 16 executes the positioning mode according to the input state from the GPS receiver 1 and the temperature sensor 9 and the arithmetic control according to the program according to the program stored in the ROM 17 according to the procedure shown in FIG. I do.

When the procedure starts, first, the detected value of the temperature sensor 9 is read (step 101), and it is determined whether frequency characteristic information (hereinafter referred to as drift information) of the TCXO 8 corresponding to the detected value is stored in the RAM 20. Is determined (step 102). If it is determined in step 102 that there is corresponding drift information, the process proceeds to step 103.

In step 103, the drift information corresponding to the corresponding temperature stored in the RAM 20 is fetched (step 103), and the measurement is executed in the normal high-speed positioning mode after step 114.

If it is determined in step 102 that there is no drift information corresponding to the detected value, it is determined whether there is at least two pieces of approximate drift information close to the drift information corresponding to the corresponding detected temperature. , Step 104
Is determined.

If it is determined that the approximate drift information is present, a drift amount for the approximate drift information is extracted (step 105), and an operation by an interpolation method (also referred to as an interpolation method) is executed. The result is calculated as virtual drift information (step 106), and then the high-speed positioning mode from step 114 is executed.

On the other hand, if it is determined in step 104 that there is no approximate drift information, step 107
A positioning mode for performing a frequency search in all the subsequent bands is executed.

Here, in the GPS receiver 1 according to this embodiment, in the initial stage of its use, for example, in a default setting state immediately after factory shipment, the drift information stored in the RAM 20 is 0 to basic information. Is only stored. Therefore, in the initial stage of use, there is a high possibility of the full-band search mode from step 107 onward.

That is, in this positioning mode, the band of the search frequency is widened, the frequencies of all the bands are searched and synchronized (steps 107 to 108).

The time required for the positioning is long as in the conventional case. However, the Doppler amount obtained by the positioning is read from the synchronous circuit, and the temperature drift is calculated (steps 109 and 110). The drift information at the temperature at the time of the measurement is obtained.

This temperature-drift information is obtained as follows.

Temperature drift = (Doppler amount calculated from positioning result and satellite position information) − (Doppler amount by synchronous circuit)

This drift information is written in the RAM 20 (step 112), and the drift information is stored at an address corresponding to the temperature, and is used as temperature compensation data at the next measurement. .

On the other hand, in the high-speed positioning mode, the presence or absence of almanac information is determined (step 114). If the information is present, the Doppler amount is calculated in step 115, and the Doppler amount and the drift amount are converted into a synchronous circuit. (Step 117), high-speed synchronization can be achieved (step 117).

If it is determined in step 114 that there is no almanac information, a frequency search is performed centering on the obtained drift amount, and synchronization is performed (step 119).
Move to step 120. Note that almanac data is automatically updated regardless of whether or not it is present.

In step 120, it is determined whether or not the virtual drift information has been used. If the virtual drift information has not been used, the processing procedure ends. On the other hand, if it is determined in step 121 that the virtual drift information has been used, steps 111 to 113 are executed to obtain the temperature drift at that time, and the drift information is stored in the RAM.
Is written to.

Now, according to the GPS receiver 1 configured as described above, T.sub.
If there is no drift information of the CXO 8 and there is no approximate drift information at the approximate temperature, it takes a long time to measure. However, when measuring at the same temperature or with the approximate drift information, high-speed positioning is performed. Becomes possible.

Further, as the number of times the GPS receiver 1 is used increases, the drift information in the RAM 20 increases. Therefore, the AI function is updated every time the user uses the GPS receiver 1, and as the number of uses increases, the total temperature increases. High-speed positioning in the area becomes possible, and the positioning accuracy is also improved.

The TCXO8 has a temperature drift of 1 p.pm at -40 ° C. and 3 p.pm at + 70 ° C., for example.
The operating temperature range is, for example, −30 ° C. to + 80 ° C., whereas when a SiIC sensor or the like is used as the temperature sensor, the measured temperature range is −100 ° C. to + 150 ° C.
° C, it is possible to perform temperature compensation over the entire use temperature range of TCXO8.

[0034]

As described in detail in the above embodiment, the GPS receiver according to the present invention has no frequency characteristic information in the initial state of the GPS receiver.
Alternatively, when there is only initially set limited frequency characteristic information, it is often executed in a positioning mode in which frequency search is performed in the entire band, but every time positioning is performed, the frequency characteristic information is written to the storage unit. Therefore, the accuracy of the frequency measurement information is sequentially increased, and the positioning can be performed in a short time every time the frequency of use by the user increases.

Even when there is no corresponding frequency characteristic information, the frequency characteristic corresponding to the temperature virtually corresponding to the temperature is obtained from the frequency characteristic corresponding to the temperature already stored in the storage means from the read temperature. By determining the information, the positioning can be performed in a short time, and accurate frequency characteristic information after the positioning can be stored as data.

For this reason, in the present invention, the TCXO frequency variation is measured in a wide range in advance, and the data is stored in the ROX.
Since there is no need to write in M or the like, and it is sufficient to ship the factory with the minimum settings, it can be provided at low cost and TCXO with low temperature stability is not subject to temperature regulation of TCXO. , TCXO itself has the advantage that it can be configured at low cost.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a hardware configuration of a GPS receiver according to the present invention.

FIG. 2 is a flowchart showing a positioning processing procedure of the receiver.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 GPS receiver 2 Antenna 6 Digital processing circuit 7 TCXO 8 Temperature sensor 20 RAM for temperature drift table (storage means) 16 CPU (reading, judgment, switching command, calculation, writing means)

Claims (1)

[Claims] An antenna for receiving radio waves transmitted from artificial satellites, and radio waves transmitted from a plurality of artificial satellites received via the antennas are converted into digital signals for arithmetic processing,
GPS equipped with a signal processing circuit for obtaining coordinate values on the earth
In the receiver, a reference oscillator that supplies a high-frequency signal for frequency conversion to the signal processing circuit, a temperature sensor disposed near the reference oscillator, and a storage that stores frequency characteristic information corresponding to a temperature of the reference oscillator. Means, comparing the storage content of the storage means and the detection value of the temperature sensor, determining the presence or absence of frequency characteristic information corresponding to the detected value and the presence or absence of approximate frequency characteristic information of the detected value, When it is determined that the frequency characteristic information is present in the determination unit, a high-speed positioning mode to narrow the search range of the received radio wave is executed, when the determination unit determines that there is the approximate frequency characteristic information, After calculating the virtual frequency characteristics by interpolation, the high-speed positioning mode is executed, and when the determination means determines that there is no approximate frequency characteristic information, the reception is performed. A switching command means for executing a positioning mode in which a radio wave search range is set to a wide band; and when the determination means determines that there is the approximate frequency information, and when it is determined that there is no approximate frequency characteristic information, An arithmetic unit for calculating a frequency of the reference oscillator corresponding to a corresponding temperature based on the Doppler amount calculated in each of the positioning modes; and a writing unit for writing an arithmetic result of the arithmetic unit to the storage unit. A GPS receiver, characterized in that: