JPH06289117A - Gps receiver having conjecturing sensor - Google Patents

Abstract

PURPOSE:To shorten time from the point of time when continuous positional detection becomes impossible till the restarting of positional detection by obtaining a relative velocity between a satellite and a vehicle from the position and velocity of the vehicle determined through dead-reckoning navigation, and obtaining the quantity of Doppler shift of received frequency from the relative velocity. CONSTITUTION:When the reception of a satellite signal becomes impossible, the Doppler shift quantity forming means 1 of an initial value setting means 4 obtains a relative velocity vector between a vehicle and each satellite from the position and velocity of the satellite which are estimated on the almanac data of the satellite and the position and velocity of the vehicle which are conjectured on the data of sensors 28 to 30 for the distance, direction and velocity of the vehicle for obtaining the Doppler shift quantity of carrier frequency between the vehicle and each satellite. In addition, timing for accurately synchronizing a C/A code with a satellite atomic clock is formed on a distance between the satellite and the vehicle to generate 18 the C/A code, and the frequency shift quantity equivalent to the Doppler shift quantity is set up 3 in a C/A code tracking means 19 as the initial value. Thus at the time of restarting the receiving of the satellite signal, the frequency can be instantly tuned to the satellite signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a GPS (Global Positioning System) using satellites covering the entire globe, and in particular, in the present invention, when the GPS mounted on a vehicle cannot continuously perform positioning. Related to shortening the repositioning start time.

[0002]

2. Description of the Related Art Conventionally, there have been techniques described below as techniques in such a field. GPS is a worldwide radio wave measurement system using artificial satellites, which is being planned and implemented by the US Department of Defense. Eventually, 24 satellites, including 3 spare satellites, will be launched into each of the 6 orbital planes, 4 each. By sequentially receiving radio waves from four of these satellites, it is possible to perform three-dimensional positioning (longitude, latitude, altitude) of the receiving point.
By receiving radio waves from three satellites, two-dimensional positioning (longitude, latitude) of the receiving point is possible. In receiving satellite radio waves,
The radio signal from each satellite has a frequency of 1575.42 MHz, and the C / A code (pseudo noise (P
N) is transmitted after being spread spectrum to a digital code called code). The frequency of the radio signal of the satellite is affected by the Doppler shift and fluctuates up to ± 5 kHz according to the moving speeds of the vehicle and the satellite.
The receiver demodulates the data by synchronizing the phase of the C / A code and despreading the spectrum in synchronization with the frequency of the satellite radio wave affected by the Doppler shift.

[0003]

However, in the conventional GPS receiver, when the vehicle enters a tunnel or a shadow of a building where radio waves from the satellite are shielded, the receiver is not synchronized with the satellite radio waves. Since it falls off, when the vehicle comes out of the tunnel or the shadow of the building etc., it is necessary to newly synchronize with the satellite radio wave, but it takes a certain amount of time to obtain new synchronization and positioning is obtained. However, if the vehicle frequently enters a tunnel or gets into the shadow of a building or the like, it often happens that positioning cannot be immediately obtained when exiting from the tunnel.

Therefore, in view of the above problems, it is an object of the present invention to provide a GPS receiver which can quickly synchronize even if the radio wave is temporarily cut off.

[0005]

In order to solve the above-mentioned problems, the present invention receives a C / A code which is an identification code of a plurality of satellites, and an almanac data relating to the information of the satellites to obtain the C / A code. C / A code generating means for demodulating C / A code, and C / A code tracking for generating the C / A code of the C / A code generating means according to the frequency of the signal from the satellite and the phase of the C / A code A GPS receiver having means for positioning the vehicle is provided with a Doppler shift amount forming means, a synchronization supplementing means, and a tracking initial value setting means.

The Doppler shift amount forming means predicts the position and speed of the satellite from the almanac data, obtains the relative speed between the satellite and the vehicle from the position and speed obtained from the dead reckoning of the vehicle, and from this relative speed The Doppler shift amount of the frequency is calculated. The Doppler shift amount may be obtained after it is determined that the data cannot be received from the phase shift amount data.

The synchronization supplementing means obtains the distance between the satellite and the vehicle from the predicted position of the satellite and the estimated position of the vehicle, and from this distance, C of the C / A code generating means is obtained.
/ Form timing for generating A code. The tracking initial value setting means sets the Doppler shift amount as an initial value for frequency adjustment in the C / A code tracking means.

[0008]

According to the GPS receiver having the estimation sensor of the present invention, the Doppler shift amount forming means predicts the position and velocity of the satellite from the almanac data, and obtains the position and velocity obtained from the dead reckoning of the vehicle. From this, the relative velocity between the satellite and the vehicle is obtained, and the Doppler shift amount of the frequency is obtained from this relative velocity. The Doppler shift amount may be obtained after it is determined that the data cannot be received from the phase shift amount data. In the synchronization supplementing means, the distance between the satellite and the vehicle is obtained from the predicted position of the satellite and the estimated position of the vehicle, and the distance is accurately transmitted to the atomic clock mounted on the satellite. C /
The C of the C / A code generating means is synchronized with the A code.
/ A code can be generated. In the tracking initial value setting means, the Doppler shift amount is the C / A.
It is set as an initial value for frequency matching by the code tracking means. Therefore, even if the vehicle temporarily loses synchronization with the satellite due to entering a tunnel, the initial value of the Doppler shift amount is given during repositioning, and the C / A code can be searched at a timing very close to the synchronization. , The time required to start repositioning can be shortened.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a GPS receiver having an estimation sensor according to an embodiment of the present invention. The GPS receiver having the estimation sensor shown in the figure firstly includes the antenna 10. The antenna 10 has a unique C from a plurality of artificial satellites.
/ Receives a transmission signal modulated with an A code. This transmission signal is phase-modulated with a digital code called C / A code having a carrier frequency of 1575.42 MHz. This C / A code is called a pseudo noise code (PN), and there are 36 types of patterns, and different C / A codes are assigned to each satellite, which is known to the user. This C / A code has a chip rate of 1.02
3 Mbps, code length 1023 bits (1 ms)
Is. The above-mentioned phase modulation is called spread spectrum, and enables each satellite to be identified even at the same frequency.
Further, data required for positioning called "navigation message" is superimposed on the C / A code. This navigation message includes orbital information of each satellite, correction values of atomic clocks mounted on the satellites, propagation delay correction counts by the ionosphere, and general information (almanac data) of all satellites. The navigation message has a chip rate of 50 bps,
One mainframe is constructed in 30 seconds. The ground station of the satellite has a measurement system for the precise orbital elements of the satellite, and in addition to operation management to maintain an accurate orbit, G
In order to maintain the PS function, daily corrections such as time bases, orbital elements, position correction parameters, etc. are made and quality control is performed.

Returning to FIG. 1, the RF amplifier 11 connected to the antenna 10 receives the R signal received by the antenna 10.
Amplify the F signal. The reference oscillator 12 is a temperature-compensated crystal oscillator and forms a reference signal. The local oscillator 13 connected to the reference oscillator 12 converts the frequency of the signal from the RF amplifier 11 from 1575.42 MHz to an intermediate frequency of 4.0.
A signal for local oscillation is formed for conversion into a 92 MHz signal (IF signal). The mixer 14 connected to the RF amplifier 11 mixes the RF signal from the RF amplifier 11 with the signal from the local oscillator 13 to convert the RF signal into an intermediate frequency signal. An intermediate frequency filter amplifier 15 connected to the mixer 14 outputs the signal converted by the mixer 14 by about 1
Amplify 10 dB. A / D converter (Analog to Digital Converte) connected to the intermediate frequency filter amplifier 15
r) 16 converts the analog signal amplified by the intermediate frequency filter amplifier 15 into a 1-bit digital signal. The mixer 17 connected to the A / D converter 16 sequentially performs, for example, spectrum despread demodulation on digital signals from each satellite. The C / A code generating means 18 for supplying the C / A code to the mixer 17 sequentially generates the C / A codes of the satellites used for positioning. A /
The C / A code tracking means 19 connected to the D converter 16 uses the reference signal of the reference oscillator 12 to synchronize with the carrier frequency whose frequency and phase are shifted during propagation. The code generation means 18 will generate a C / A code. The C / A code tracking means 19 forms a delay lock loop, and surveys at about 100 types of frequencies for a maximum Doppler shift of about ± 5 kHz,
The phase is surveyed at a sampling period of 2.026 MHz with respect to the chip rate of C / A code of 1.023 Mbps. Further, the generation of the C / A code is reset based on the accurate distance between the vehicle equipped with the receiver and the satellite, and the timing of synchronization is taken. In this way, the C / A code in the C / A code generating means 18 is generated by the signal synchronized with the carrier frequency and phase of the satellite radio wave. For these reasons, it is expected that a certain amount of time will be required for frequency adjustment and timing adjustment when a new synchronization is taken once the synchronization is lost.

The decoding unit 20 connected to the mixer 17 has a code for decoding the navigation message superimposed on the synchronized C / A code. The mixer 21 connected to the mixer 17 has a synchronized C /
The A code is mixed with the code from the decoding unit 20 and decoded. A low-pass filter 22 connected to the mixer 21 extracts a signal having a chip rate of 50 bps, and a data filter 23 connected to the low-pass filter 22 orbit information of each satellite and an atomic clock mounted on the satellite. The bit synchronization means 24 connected to the data filter 23 extracts the correction value, the propagation delay correction count by the ionosphere, the outline information (almanac data) of all satellites, etc.
A sync signal for data extraction is output to 3.

A topler counter 25 connected to the C / A code tracking means 19 uses the reference signal of the reference oscillator 12 and a Doppler shift amount by a decoding signal of the decoding part 20 from a signal synchronized with the carrier frequency and phase. , C
The phase shift amount of the / A code is derived. The clock forming means 26 connected to the reference oscillator 12 forms a clock signal used for forming data to be processed by the microcomputer 27 described later. The C / A code generating means 18, the C / A code tracking means 19, the data filter 23, the topler counter 25, the clock forming means 2
The microcomputer 27 connected to the CPU 6 has a central processing unit, an interface circuit for communicating with the outside, a ROM (R
EAD ONLY MEMORY), RAM (Random Access Memory), etc., and positioning derivation means for holding the almanac data etc. in the RAM to obtain positioning in order to speedily perform the next positioning, and further the features of the present invention The initial value setting means 4 is provided for performing speedy processing in the case of out of synchronization. The mixer 17 and the C / A code generating means 1
8, C / A code tracking means 19, topler counter 2
5 and the like are formed by a DSP (Digital Signal Processor) and are controlled by the microcomputer 27.

A distance sensor 28, a direction sensor 29 and a speed sensor 3 for inputting signals to the microcomputer 27.
0 is provided. The distance sensor 28, the direction sensor 29, and the speed sensor 30 are used for so-called dead reckoning. The distance sensor 28 is, for example, a Hall element sensor inserted in the speedometer cable outlet of the transmission, It consists of a circular magnet that rotates with the speedometer cable and is magnetized with 16 poles on the outer circumference. An output signal of 8 pulses per rotation is generated by the Hall element sensor, and the traveling distance of the vehicle is derived from this output signal. The azimuth sensor 29 detects, for example, the geomagnetic direction with respect to the vehicle itself, and includes a permalloy core on the ring, an exciting coil that is wound around the permalloy core and applies an AC voltage, and goes straight to the ring. It consists of two winding coils. In this case, the output voltages V1 and V2 of the two coils are V1 = αHE sin θ, V2 =, where θ is the angle of the vehicle with respect to the geomagnetic vector.
αHE cos θ. (Where HE is the magnitude of the geomagnetism) Therefore, θ ⁼ tan - V2 / V1 vehicle traveling direction can be known with respect to the geomagnetism by determining the. The speed sensor 30 is installed, for example, in the middle of the speedometer cable, and includes a photo interrupter and a shutter,
An output signal of 8 pulses is output for each rotation of the cable, and the speed of the vehicle is derived from this output signal.

The display 31 connected to the microcomputer 27 outputs the position, speed and direction of the vehicle. FIG. 2 is a diagram showing a configuration of data processing of the microcomputer of FIG. As shown in the figure, the microcomputer 27 has a C / A code control 5 for designating the C / A code of the satellite to be synchronized with the C / A code generating means 18.

Further, the microcomputer 27 comprises a positioning derivation means 6. The positioning derivation means 6 derives the pseudo distance RP from the phase shift amount from the topler counter 25, and positions the vehicle from the satellite data of the data filter 23 by the following formula. RPi = [(ui −x) ² + (vi −y) ² + (wi −
z) ² ] ^1/2 + CΔtr where the vehicle position is x, y, z, the pseudo range with each satellite is RPi, and the satellite position is ui, vi, wi (i = 1,2,
3, 4). The positions ui, vi, and wi of each satellite are obtained by solving the Kepler's equation from the orbital parameters in the navigation message. The position of each satellite can be predicted in advance from orbital data. C is the speed of light and Δtr is G
Indicates the difference between the PS reference time and the receiver clock. Further, the positioning derivation means 6 stores the almanac data from the data filter 23.

The initial value setting means 4 of the microcomputer 27 includes a Doppler shift amount forming means 1. In the Doppler shift amount forming means 1, when a vehicle enters a tunnel or a shadow of a building or the like makes it impossible to receive a signal from a satellite, a phase shift cannot be obtained from the data from the topler counter 25 and reception is impossible. to decide. Then, the position and speed of the satellite are predicted from the Almac data of the satellite. Further, the position of the vehicle is estimated from the data of the distance sensor 28 and the direction sensor 29. A relative velocity vector between the vehicle and each satellite is derived from the estimated position of the vehicle, the velocity from the velocity sensor 30, and the predicted position and velocity of the satellite. The Doppler shift amount of the carrier frequency between each satellite is derived from the relative velocity vector with each satellite.

The initial setting means 4 comprises a synchronization acquisition means 2. In the synchronization acquisition means 2, the position of the satellite is predicted from the Almac data of the satellite from the positioning derivation means 6, and the position of the vehicle is estimated from the data from the distance sensor 28 and the direction sensor 29. Predict the distance between the two from the position. From this distance, the timing shift of the C / A code that is accurately synchronized with the atomic clock mounted on the satellite is obtained. From this shift, the timing for synchronizing the C / A code is formed. Then, at this timing, the code of the C / A code generating means 18 is generated through the C / A code control 5.

The initial setting means 4 comprises a tracking initial value setting means 3. In the tracking initial value setting means 3, the shift amount of the frequency corresponding to the Doppler shift amount formed by the Doppler shift amount forming means 1 is described as an initial value C
/ A code tracking means 19 is set. Therefore, according to the present embodiment, immediately after the vehicle exits the tunnel or the like, the Doppler shift amount and the synchronization timing that are offset during the period in which the signal from the satellite cannot be received are corrected,
The frequency can be instantly adjusted to the radio wave received from the satellite, and the timing of synchronization can be taken.

[0019]

As described above, according to the present invention, the position and speed of the satellite are predicted from the almanac data, and the relative speed between the satellite and the vehicle is obtained from the position and speed obtained from the dead reckoning of the vehicle. The Doppler shift amount of the frequency is obtained from this relative speed, and the C / A code is sent in synchronization with the C / A code sent from the satellite according to the distance between the predicted vehicle position and the estimated vehicle position and the vehicle position. Generate code,
Since the Doppler shift amount is set as the initial value for frequency adjustment, even if the vehicle enters the tunnel and is temporarily out of synchronization with the satellite, the C / A code is close to the frequency from the satellite and close to the synchronization when repositioning. Can be generated, and C /
The time required for searching the A code can be shortened.

[Brief description of drawings]

FIG. 1 shows a G having a guessing sensor according to an embodiment of the present invention.
It is a figure which shows a PS receiver.

FIG. 2 is a diagram showing a configuration of data processing of the microcomputer of FIG.

[Explanation of symbols]

 1 ... Doppler shift amount forming means 2 ... Synchronization supplementing means 3 ... Tracking initial value setting means 4 ... Initial setting means 18 ... C / A code generating means 19 ... C / A code tracking means 25 ... Topler counter 27 ... Microcomputer 28 ... distance sensor 29 ... direction sensor 30 ... speed sensor

Claims (1)

[Claims] 1. A C / A code generating means (18) for receiving a C / A code, which is an identification code of a plurality of satellites, and almanac data concerning satellite information, and demodulating the C / A code. The C / A code generating means (18) according to the frequency of the signal from the satellite and the phase of the C / A code.
C / A code tracking means for generating the C / A code of (1
A GPS receiver having 9) for positioning a vehicle, the satellite position and velocity being predicted from the almanac data,
Doppler shift amount forming means (1) for obtaining the relative velocity between the satellite and the vehicle from the position and velocity obtained from the dead reckoning of the vehicle, and for obtaining the Doppler shift amount of the frequency from this relative velocity, and the predicted satellite From the position and the estimated position of the vehicle, the distance between the satellite and the vehicle is calculated, and from this distance, the C /
The Doppler shift amount is set as an initial value for frequency adjustment in the synchronization supplementing means (2) for forming the timing of generating the C / A code of the A code generating means (18) and the C / A code tracking means (19). GP having an estimation sensor including tracking initial value setting means (3)
S receiver.