JP2921435B2 - Positioning signal receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a GPS (Global Positio).
The present invention relates to a positioning signal receiver suitable for being applied to a receiver of a positioning system using a satellite called a "ning system".

[0002]

2. Description of the Related Art Conventionally, various receivers of a positioning system using a satellite called GPS have been developed. Positioning by the receiver is performed by receiving positioning signals transmitted from a plurality of (about 24) satellites orbiting the earth, demodulating information included in the positioning signals from each satellite, and demodulating the information. The information is analyzed to determine the current position. In this case, the information contained in the positioning signal transmitted from each satellite includes time data of the satellite, orbit data for calculating the position of the satellite, and the like. The positioning signal containing these information is spread spectrum modulated. At the same time, the signal is transmitted after being subjected to quadrature phase modulation (two-phase PSK modulation) by two carriers. The frequencies of these two carrier waves are the same for all satellites (1227.6 MHz and 1575.42 MHz), and the codes used for spread spectrum modulation are different for each satellite.

At the time of positioning, positioning signals from at least three satellites are received at the same time, and information contained in the received positioning signals from the three satellites is demodulated. Analysis is performed to perform position measurement. For this reason, a GPS receiver is provided with a plurality of channel receivers, and each receiver captures a positioning signal from another satellite one by one.

[0004]

By the way, in such a GPS receiver, accurate positioning can be performed only after a positioning signal from a satellite is captured by a receiving unit of each channel, but the positioning signal is captured. It takes time to do
There is an inconvenience that it takes time from the start of reception by the receiver to the positioning of the current position. That is, the positioning signal transmitted from each satellite has a fixed frequency defined when transmitting from the satellite, but is actually received by the receiver due to the Doppler effect due to the relative speed between the satellite and the receiver. There are variations in frequency. Therefore, in order to accurately capture the positioning signal from each satellite, search processing is performed to change the reception frequency until a signal from the satellite can be received within the frequency range in which the signal from the satellite is considered to exist. ,
It took time before satellite signals could be captured and positioned.

[0005] Furthermore, it takes a long time to capture a signal from a satellite in such a GPS receiver. In addition to the frequency fluctuation due to the Doppler effect, there is a problem in the oscillation accuracy of an oscillator provided in the receiver. That is, if the oscillation frequency of the oscillator included in the receiver fluctuates for some reason, the reception frequency of the receiver fluctuates correspondingly. It cannot be captured. Therefore, at the time of the search for changing the reception frequency described above, it is necessary to set a wide range in which the reception frequency is changed in consideration of the oscillation accuracy of the oscillator, and at the time of capturing a signal from a satellite, it is necessary to perform a search over a wider frequency range. was there.

The present invention has been made in view of the above circumstances, and has as its object to reduce the time required for signal acquisition for positioning.

[0007]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides a frequency signal oscillating means for determining a receiving frequency of a positioning signal, a temperature sensor for detecting the temperature of the oscillating means, and a temperature sensor. Storage means for storing correction data for correcting the drift of the oscillation frequency of the oscillation means based on the detected data.

[0008]

According to the present invention, the drift of the oscillation frequency of the oscillating means is corrected by the correction of the receiving process based on the correction data, so that the adverse effect due to the temperature fluctuation of the oscillating frequency of the oscillating means can be eliminated. Accurate positioning signal acquisition processing becomes possible.

[0009]

An embodiment of the present invention will be described below with reference to the accompanying drawings.

In this embodiment, the present invention is applied to a receiver of a positioning system using an artificial satellite called GPS, and FIG. 1 shows a configuration of the receiver. The receiver includes an antenna 11 for receiving a positioning signal from a satellite (this positioning signal is a spread spectrum signal).
Is connected to an amplifier 12, supplies the received signal amplified by the amplifier 12 to a mixer 14 via a band-pass filter (BPF) 13, and the mixer 14 uses the PLL circuit (phase locked loop circuit) 32 , And frequency-converts a received signal of a predetermined frequency (1.5 GHz band) into a first intermediate frequency signal.

In this case, the frequency signal output from the PLL circuit 32 is a signal generated by dividing a substantially constant frequency signal output from the crystal oscillator 31 by a frequency divider in the PLL circuit 32, and the frequency signal is divided. By controlling the ratio and the like, the frequency of the signal output from the PLL circuit 32 changes. The oscillation frequency of the PLL circuit 32 determined by the frequency division ratio and the like is controlled by a central controller 35 described later.

The first intermediate frequency signal output from the mixer 14 is passed through a band-pass filter 15 to the mixer 16.
To supply. This mixer 16 converts the first intermediate frequency signal into
An almost constant frequency signal output from the crystal oscillator 31 is mixed and frequency-converted into a second intermediate frequency signal.

The second intermediate frequency signal output from the mixer 16 is supplied to a demodulation unit 19 via a high-pass filter (HPF) 17 and an amplifier 18, and a GPS positioning signal is demodulated. The demodulation processing in the demodulation unit 19 includes spectrum despreading processing by multiplying the second intermediate frequency signal by a PN code (pseudo random code), and demodulation of transmission data by PSK demodulation of the spectrum despread signal. Processing to obtain data (time data, orbit data, etc.) transmitted from the satellite. In this case, the PN code used for the spectrum despreading processing is a value determined for each satellite, and the satellite to be received can be selected by selecting the PN code. The selection of this receiving satellite (ie, P
The central control unit (CPU) 35 which is a microcomputer for controlling the receiving operation of the receiver is selected.
The central control unit 35 determines whether a desired satellite has been captured by the demodulation unit 19.

The demodulation unit 19 of the present embodiment is capable of simultaneously performing a plurality of demodulation processes (eg, demodulation processes of eight channels), and is capable of receiving and demodulating positioning signals from a plurality of satellites at the same time. It is. The configuration for simultaneously performing the plurality of demodulation processes includes a case where there are a plurality of demodulation circuits themselves and a case where one or several demodulation circuits perform acquisition processing of different satellites in a time-division manner. In some cases, positioning signals from satellites exceeding the number of circuits are received and demodulated at the same time.

The transmission data from each satellite obtained by demodulation by the demodulation unit 19 is supplied to an arithmetic processing unit 20, and the orbit of each captured satellite indicated by the transmission data and the signal from each satellite are transmitted. (Determined by the phase of the PN code generated at the time of spectrum despreading), and the current position is calculated by an operation using the determined data. As a process of calculating the current position, for example, when positioning signals from four GPS satellites can be acquired at the same time, the positions of the four satellites at a certain time are received and obtained in orbit data. The distance between each satellite and the positioning point (current position) is calculated from the detected propagation delay,
The position of the positioning point is obtained by solving a quaternary simultaneous equation derived from the position data and the distance data of these satellites.

The data of the calculated current position is supplied to the display unit 21. The display unit 21 displays the supplied current position in a predetermined manner (for example, display of latitude, longitude, and altitude).
Let it. Alternatively, in the case of a receiver for a navigation device, the current position and a map near the current position are displayed on the display unit 21.

In this embodiment, a temperature sensor 32 is provided in the vicinity of the position where the crystal oscillator 31 is arranged, and temperature data detected by the temperature sensor 32 (voltage data whose potential changes in proportion to the temperature) is converted into an analog signal. Digital converter 34
The analog / digital converter 34 converts the digital data into digital data corresponding to the potential, and supplies the converted digital data to the central controller 35. The central controller 35 includes a memory (not shown) for storing the supplied temperature data and the data of the drift amount of the oscillation frequency of the oscillator 31 at that time, and sequentially stores the data in this memory. . In this case, the drift amount of the oscillation frequency of the oscillator 31 can be detected when the signal from the satellite is captured by the search processing and the current position can be measured. That is, in the case of the positioning system by GPS,
When the signal from the satellite is captured by the search process and the current position can be located, the exact oscillation frequency of the oscillator 31 can be determined by a predetermined calculation.
The data of the difference from the frequency determined so that the oscillator 31 oscillates is stored together with the temperature data as the data of the drift amount. The storage state of the temperature data and the drift amount data will be described later.

Under the control of the central controller 35, when the signal from each satellite is captured by the demodulation unit 19, the temperature data detected by the temperature sensor 33 at that time and the temperature data stored in this memory are stored. And the drift amount data are used to shift the frequency range in which signals from the satellite are captured and processed. That is, the central controller 35 determines the temperature data detected by the temperature sensor 33, refers to the stored data of the corresponding temperature in the memory, and estimates and estimates the drift amount of the oscillation frequency of the oscillator 31 at that time. The frequency range in which the received data is searched by the demodulation unit 19 is offset by the drift amount (that is, the search range is changed).
Perform control.

Next, a state where temperature data and drift amount data are stored in a memory in the central control unit 35,
Processing for estimating the drift amount based on the storage state will be described.

First, the state of storing the temperature data and the drift amount data in the memory will be described. The data is stored as shown in Table 1 below.

[0021]

[Table 1]

The temperature representative values T _1x , T _2x , T shown in Table 1
_3x , T _4x , ΔT _kx , and ΔT _nx are temperatures set at predetermined intervals within a temperature range in which the GPS receiver may be used. For example, when the temperature range in which the receiver can be used is approximately −20 ° C. to + 50 ° C., a value set every 10 ° C. within this range (eg, −20 ° C., −10 ° C.)
° C, ± 0 ° C, + 10 ° C, + 20 ° C, + 30 ° C, +40
° C., + at 50 ° C.), the temperature representative value T _1x through T _nx is are predetermined values stored in the memory.

When the positioning signal from the GPS satellite is actually received, the central controller 35 monitors the temperature detected by the temperature sensor 33 at that time, and the temperature at that time is represented by each temperature representative value. When the temperature becomes close to one of the values of T _{1x to} T _nx , the detected temperature at that time and the drift amount of the oscillation frequency of the oscillator 31 obtained by the positioning calculation at that time are represented by the corresponding temperature representative value. The temperature and the drift amount of the immediately preceding temperature are stored in the data storage area. For example, the temperature representative value T
When it detects a temperature T ₁₁ close to _1x (for example, when it detects a temperature in the range of ± 2 ℃ representative temperature value), and a drift amount D ₁₁ of the temperature T ₁₁ and the frequency at that time, the temperature representative value T _1x Is stored in the data storage area of the temperature and the drift amount one immediately before corresponding to.

A plurality of data storage areas of the temperature and the drift amount for each of the temperature representative values T _{1x to} T _nx are prepared for each of the temperature representative values, and the number of data storage areas is m (m is an arbitrary integer:
If a new data is stored in the previous temperature and drift amount data storage area up to a temperature and drift amount data storage area of up to about 3), each area of the temperature representative value is stored. Are sequentially moved to the previous storage area one by one. Then, the data stored in the data storage area of the m-th previous temperature and drift amount (that is, the oldest data related to the representative temperature value) is deleted.

[0025] Then, for each temperature representative value T _1x through T _nx, m pieces of temperature corresponding to the respective temperature representative value T _1x through T _nx,
The average temperature of the stored data of the drift amount, and the average drift determined by the arithmetic processing of the central control device 35, the mean temperature T ₁ of its _{value, T 2, T 3, T} 4, ‥‥ T k, ‥‥ T _n and the average drift amount _{D 1, D 2, D 3} , D 4, ‥‥ D k, as ‥‥ D _n, is stored in the corresponding area.

Therefore, every time new data is stored in the temperature and drift amount data storage area immediately before the representative temperature values T _{1x to} T _nx , the average temperature and the average drift amount of the representative temperature values are calculated. Data is updated.

When positioning is performed by this GPS receiver using the data stored in the memory as described above, the drift amount of the oscillation frequency of the crystal oscillator 31 is estimated. This estimated drift amount D is calculated based on the following equation, where the current temperature obtained by the temperature sensor 33 is T (T _k <T <T _{k + 1} ).

[0028]

(Equation 1)

The calculation of the drift amount based on the equation (1) is performed according to the principle shown in FIG. In other words, the detected current temperature T is the measured average value T _{k of} a certain temperature representative value T _{kx and} the measured average value T _k of the temperature representative value T _{kx + 1 immediately} above it.
When the value is between _{k + 1} and _{k + 1} , the average values T _k and T _{k + 1} are plotted on the horizontal axis, and the average drift amounts D _k and D _{k + 1} corresponding to the respective average values are plotted on the vertical axis. Then, a straight line α connecting both points is obtained. Then, the drift amount D of the current temperature T during that time is detected using the straight line α.

Then, the PLL is controlled by the central controller 35 by the frequency corresponding to the obtained drift amount D.
The frequency output by the circuit 32 is changed to perform a process of removing a frequency variation due to a temperature, and a search process of acquiring a positioning signal from a satellite is performed based on the drift-corrected frequency.

Next, a search process for capturing a positioning signal from the satellite will be described with reference to the flowchart of FIG. First, when a search process for capturing a satellite is started (step 101), the central control device 35 sends the temperature sensor 3
3 to determine the current temperature detected from the crystal oscillator 31
Estimate the offset of the oscillation frequency (step 10)
2). This estimating process uses the data stored in the memory shown in Table 1 described above to make an estimation based on Expression (1).

When the offset of the oscillation frequency of the crystal oscillator 31 is estimated, the center frequency of the frequency range in which the demodulator 19 searches for a positioning signal from a satellite is shifted by the estimated offset (step 10).
3). Then, the frequency to be demodulated by the demodulation unit 19 is slightly changed up and down around the shifted center frequency, and a positioning signal from the satellite is captured. Here, it is determined whether or not the positioning signal from the satellite has been captured, that is, the demodulation unit 19
Then, it is determined whether or not the positioning signal from the satellite has been successfully demodulated (step 104). When it is determined that the positioning signal has been successfully captured, reception at that frequency is continued, and the satellite search process ends (step 105).

If no signal from the satellite is detected in step 104, the frequency searched by the demodulation unit 19 is changed (step 106). Then, after the change, it is determined whether or not the entire area set to detect the signal has been searched (step 107). If the entire area has not been searched, the process returns to step 104 and returns to step 104. Judgment as to whether or not the capture is successful and frequency change when the capture is not possible are repeatedly performed. If it is determined in step 107 that all areas have been searched, step 1
Returning to step 02, the offset frequency is set again based on the temperature detected by the temperature sensor.

In this way, by performing the search process by correcting the frequency at which the signal from the satellite is captured by the demodulation unit 19 based on the temperature, the time required for the search process can be reduced. That is, even if the oscillation frequency of the crystal oscillator 31 fluctuates due to a temperature change, the frequency demodulated by the demodulation unit 19 is appropriately corrected, and the center frequency when searching for a positioning signal from a satellite is always set to an appropriate frequency. In anticipation of fluctuations in the oscillation frequency of the oscillator due to temperature,
The search frequency range can be narrowed as compared with the conventional receiver in which the search frequency range is widened, and the search time until receiving positioning signals from three or four satellites required for positioning is obtained. Can be shortened, and the time from the start of the positioning operation to the actual positioning can be shortened.

In addition to shortening the positioning time at the start of positioning, signals from satellites captured for some reason
The time required for re-acquisition in the case where re-acquisition is performed when the user has temporarily lost sight can also be shortened.

In the above-described embodiment, the average drift amount used for calculating the drift amount of the oscillator and the average temperature are obtained from a simple average of the data stored in the memory in the central control unit 35. However, the past temperature and drift amount data stored in the memory and the newly stored temperature and drift amount data may be weighted to obtain the average temperature and the average drift amount. good.

For example, the newly detected temperature and drift amount data T _k and D _k, and the immediately preceding temperature and drift amount data T _k1 and D _{k1 to} m-th previous temperature and drift stored in the memory. The average data T _km and D _km may be multiplied by different weighting factors a, b and c ‥‥ m to obtain the average temperature T _kx and the average drift amount D _kx as in the following equations.

[0038]

(Equation 2)

By calculating the average by weighting as described above, the average data is calculated while respecting the past data, and good data which does not depend on a temporary error in the temperature measurement value can be obtained. Thus, good temperature correction can always be performed.

In the above embodiment, a plurality of past temperatures and a drift amount at that time are stored for each temperature representative value. Then, the weighting coefficient may be set to 1: 1 and the average temperature T _kx and the average drift amount D _kx may be obtained based on the following equation and stored in the memory.

[0041]

(Equation 3)

By doing so, the amount of data stored in the memory can be reduced, and the storage capacity of the memory can be reduced.

The receiving circuit shown in the above embodiment is an example, and can be applied to a positioning signal receiving circuit having another configuration. That is, if the temperature of the frequency signal generating means for determining the reception frequency is detected and the reception frequency range or the reception frequency itself is corrected based on the temperature, the reception circuit of the positioning signal of various circuit configurations may be used. Applicable to Further, in the above embodiment, the present invention is applied to the GPS receiver, but it is needless to say that the present invention can be applied to other positioning system receivers.

[0044]

According to the present invention, the drift of the oscillation frequency of the oscillating means is corrected by the correction of the reception processing based on the correction data, so that the adverse effect due to the temperature fluctuation of the oscillating frequency of the oscillating means can be eliminated. As a result, accurate positioning signal capture processing without the influence of temperature fluctuations can be performed, and positioning signals can be quickly captured and positioned.

In this case, the oscillating frequency of the oscillating means is calculated by analysis based on the demodulated information, and the calculated oscillating frequency and the detected data of the temperature sensor at that time are stored in the storing means, and the correction is performed. Since the data is updated, correction based on the latest data is always performed.

Further, when the correction data is updated, the average value of the updated correction data and the previously stored correction data is used as new correction data, so that more accurate data can be obtained. Since the correction data is updated to higher correction data, a more accurate and quick acquisition process can be performed.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing one embodiment of the present invention.

FIG. 2 is a flowchart illustrating a process of searching for a signal from a satellite according to one embodiment.

FIG. 3 is a characteristic diagram showing a relationship between a drift amount and a temperature according to one embodiment.

[Explanation of symbols]

 14, 16 mixer 19 demodulation unit 20 arithmetic processing unit 31 crystal oscillator 32 PLL circuit (phase locked loop circuit) 33 temperature sensor 35 central control unit (CPU)

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-6-242208 (JP, A) JP-A-5-347513 (JP, A) JP-A-7-218612 (JP, A) JP-A-6-242 326516 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G01S 5/14 H03B 5/32

Claims (5)

(57) [Claims] 1. A method for receiving a plurality of positioning signals transmitted at predetermined frequencies from different positions, demodulating information included in the received positioning signals, analyzing the demodulated information, and determining a current position. In a positioning signal receiver for positioning, oscillating means of a frequency signal for determining a receiving frequency of the positioning signal, a temperature sensor for detecting a temperature of the oscillating means, temperature data detected by the temperature sensor, and oscillating of the oscillating means.
Storage means for storing the correction data in correspondence with the drift amount data of resonance frequency, in the corrected data the storage means is storing, the temperature was
Temperature data within the specified temperature range including the temperature detected by the sensor
Based on the drift amount data corresponding to
The drift of the oscillating frequency
A positioning signal receiver comprising: a control unit for determining a frequency . 2. An oscillation frequency of the oscillating means is calculated by analysis based on demodulated information, and the calculated oscillating frequency and an oscillating frequency determined by the control means are calculated.
A drift amount data determined based on the number, the oscillation hands
Stage was above <br/> SL temperature sensor is associated with the temperature data detected when oscillates at the calculated oscillation frequency data
Data and be stored in the storage means, the positioning signal receiver according to claim 1, wherein which is adapted to update the correction data. 3. The positioning signal receiver according to claim 2, wherein an average value of said updated correction data and previously stored correction data is used as new correction data. 4. A plurality of positioning signals transmitted at predetermined frequencies from different positions are received, information included in the received positioning signals is demodulated, and the demodulated information is analyzed to determine a current position. in positioning signal receiver for positioning, a temperature sensor for detecting the temperature of the local oscillation means receiving portion, the temperature data and the local oscillation means for temperature sensor detects
With the local oscillation frequency drift amount data
Storage means for storing the positive data; and the temperature sensor in the correction data stored in the storage means.
Temperature data within the specified temperature range including the temperature detected by the sensor
Local oscillation based on the drift amount data corresponding to
The local oscillation frequency drift of the
And a control means for determining a local oscillation frequency of the vibration means . 5. The search frequency range of said local oscillation means is changed by correcting said drift.
The positioning signal receiver as described.