JPS6134486A - Position measuring apparatus - Google Patents

Abstract

PURPOSE:To automatically set initial information, by receiving a signal from one artificial satellite to obtain initial information necessary for shifting to the normal operation. CONSTITUTION:A CPU8 executes a program of starting time at the start up of the operation. First, a PN signal PNS is generated from a PN signal generation circuit 7 while the center frequency of a Doppler shift locking VCO10 is set and changed sequentially until a PN lock loop and a Doppler shift lock loop are locked. With the locking thereof, the CPU8 pick up time information and orbit information of a satellite from a received signal LDA fed by a demodulation circuit 12 to compute the rough position of an observing point. Finally, the CPU8 pick up orbit information of all artificial satellites from the signal LDA and then, executes the normal operation program. This eliminates the preliminary storage of initial information.

Description

[Detailed description of the invention] [Industrial application field].

The present invention relates to a positioning device, and in particular to a GPS system (GPS) that performs positioning using data signals transmitted from artificial satellites.
global positioning system
It is suitable for application to m).

[Conventional technology]

The GPS system receives data signals such as position information and time information sent from artificial satellites to the ground at observation points, and based on the received data, the position and time of the observation point, etc.
You can know exactly what the first artificial satellite SAT is, considering the rectangular coordinate system with the origin at 41 inside the globe as shown in Figure 3.
(Let the position be (X5, yi, 2!))
A point P on the earth's surface or in the sky (X11,)Fll, 21
1) (x!-xo)"+C'ji 3111) Word+
(Zz-2,)”=((tt to)×C] 2
Based on (1), the principle is that the position and time of the observation point P can be known by calculating the unknowns.

Here, ti is the time when the data signal was transmitted from the artificial satellite, to is the time when this data signal was received at the observation point P, and C is the speed of light.

In order to solve equation (1), it is necessary to create equations for the number of unknowns, and in practice, in order to be able to observe the unknown number of satellites at the same time at observation point P, a large number of, for example, one
Eight artificial satellites are planned to orbit the earth, thus allowing the necessary equations to be developed based on data from each satellite.

For example, when using a GPS system as a positioning system, the error included in the four unknowns Xo, 3'6.26, and and position P
It is considered to obtain (Xo, '10, Zo>).

The positioning device in Figure 4 has four unknowns, namely the digit 1 of the observation point.
! It has first to fourth channel data receiving circuits DTR1 to DTR4 for solving (Xo, 3'o, 20) and the error included in the data reception time t0.

In the GPS system, satellites use frequencies 1.57542 (GHz) and 1.2276 (GHz), which belong to the L band.
(G11z) with a clock frequency of 10.
P code of 23 (MHz) and 1.023 (M
A spread spectrum signal is transmitted using a C/A code (Hz).

Here, the P code and C/A code are 1023 (chips/ms) suspicious noise signals (this is called a PN signal), and the data is 50 (bps) BPSK (binar).
y phase 5hift keying) signal is converted into P code and C/A code and transmitted.

Thus, the data transmitted from each satellite includes the coordinate position data of each satellite, relative to its orbit around the Earth □
Location data of other satellites and highly stable atomic clocks installed on artificial satellites (this is called a satellite clock)
The satellite time system is transmitted at predetermined time intervals (i.e., every 6 seconds) along with the deviation data between the time system determined based on the time system (this is called the satellite time system) and the world standard time.

In the case of the positioning device in Figure 4, the carrier frequency is 1.57542
(GHz) is received by the antenna 1, and the frequency conversion circuit 2 converts the signal to a frequency of 75.42 (MHz).
The first intermediate frequency signal IF is converted into a first intermediate frequency signal IF of l, and then applied to the multiplication circuit 3. The multiplier circuit 3 is given the frequency output LO, with a frequency of 64.72 CM ) Iz ) generated in the local oscillation circuit 4, and the frequency 10 obtained at its output terminal is
．． 7 (MHz) second intermediate frequency signal IP, is passed through a bandpass filter 5 having a relatively wide passband to the first to second intermediate frequency signals IP.
It is applied to the second multiplication circuit 6 of the fourth channel data receiving circuits DTR1 to DTR4.

Here, the first to fourth channel data receiving circuits DTRI~
The DTR 4 is configured to be able to formulate four equations based on equation (1) above by receiving data from four satellites. Each receiving circuit DTR
1 to DTR4 have the same configuration, therefore, the first
The configuration will be explained using the channel receiving circuit DTR1.

This second multiplier circuit 6 converts the spread spectrum data signal transmitted from the satellite into a PN signal PNS generated from the PN signal generation circuit 7 into a second intermediate frequency signal IP;
The despreading process is performed by multiplying the PN
The signal PNS is 1021 (chip/
m s ) code signal.

Here, each satellite is assigned a C/A code with a unique binary pattern, and the C/A code pattern assigned to all the satellites (for example, 18 satellites) in the PNN signal generation circuit 7 is The PN signal PNS having the following value can be selectively generated under the control of the CPU 8.

Thus, the PN contained in the second intermediate frequency signal IF
The phase of the signal is P generated in the PN signal generation circuit 7.
When the correlation with the N signal PNS is established, a despread output signal DKN with a high signal level is obtained at the output terminal of the multiplication circuit 6, and this is given to the third multiplication circuit 9.

The output S1 of a voltage controlled oscillator (VCO) 10 for Doppler shift locking is applied to the multiplication circuit 9, and thereby a phase shift keying signal PSS with a frequency of 455 (kHz) is sent to the output terminal.

This phase shift keying signal PSS has a narrow passband (
For example, the despread output signal DKN obtained when the despread signal DKN is applied to a band pass filter 11 having a frequency of about ±1 (kHz) and the correlation is taken is applied to a demodulation circuit 12 formed of, for example, a Costas loop. As a result, the output terminal of the demodulation circuit 12 has a
(bpS) received data LDA is demodulated and obtained, C
It is sent to P U 8.

The CPU 8 reproduces the carrier based on the received data LDA to determine the orbital position of the satellite and relative position changes between positioning devices, or the carrier frequency of the satellite and the local oscillation circuit 4.
A Doppler shift control signal DPC is given to the Doppler shift lock C010 to control its oscillation frequency in accordance with changes in the relative deviation from the oscillation frequency of the Doppler shift lock. Also, the frequency of the phase shift keying signal PSS is approximately 4
55 (kllz). Thus, a Doppler shift lock loop is formed by the demodulation circuit 12, the CPU 8, the VCOI O, and the multiplication circuit 9.

On the other hand, the phase shift keying signal obtained at the output end of the band pass filter 11 is given to the envelope detection circuit 13, and the detection output ENV is sent to the PN lock VCOI 5 through the low pass filter 14 as the oscillation frequency control signal C0.
Given as NT.

The PN lock VCO 15 has a first oscillation circuit whose oscillation frequency changes according to changes in the control signal C0NT, and a second oscillation circuit which oscillates at a predetermined frequency.
When the slide mode signal 5LID is applied from the PU 8, an oscillation frequency output S2 of a predetermined frequency is applied to the PN signal generation circuit 7 using the second oscillation circuit. At this time, the frequency of the PN signal PNS deviates from the frequency of the PN signal included in the received signal by a predetermined frequency, so that the PN
An operating mode is obtained in which the phase of the signal PNS is continuously shifted out of phase with respect to the PN signal included in the received signal. At this time, the envelope detection output ENV of the envelope detection circuit 13 is the PN signal PN as shown in FIG.
When there is a correlation between S and the PN signal included in the received signal, a peak waveform that rises in the shape of a triangular wave is exhibited, and in other sections where there is no correlation, the signal level is low.

The CPU 8 sets a threshold level L that the envelope detection signal ENv crosses when it rises to the peak value.
tk, and when the envelope detection signal ENV does not exceed the second threshold level L, this slide mode state is maintained by applying the slide mode signal SLID to the PN lock VCO 15. On the other hand, when the envelope detection signal ENV exceeds the threshold level Ltk, the slide mode signal 5
Disappear LID.

In this way, the phase of the PN signal PNS is controlled to follow the phase of the PN signal included in the received signal, thus maintaining a correlated state. As a result, a PN lock loop is formed by the envelope detection circuit 13-low-pass filter 14, CPU 8-PN lock VCO 15-PN signal generation circuit 7-multiplication circuit 6.

In addition, the positioning device has a timer J6, and is configured to measure the time when the positioning device receives a signal from the satellite. The timer 16 clocks a predetermined time (for example, 1 (s)) from a clock (this is called a user clock) installed in the positioning device.
), the clock signal CK that arrives every predetermined time (for example, 20 (ns)) is used to reset the signal, and when the epoch signal EP is given from the PN signal generation circuit 7, the reception time is determined. The count value N representing the information is sent to the CPU 8 and the count value N representing the information is sent to the CPU 8.
C' 411 L V' Q a In the configuration shown in FIG. 4, the first to fourth channel data receiving circuits DTR1
~All DTP4 are in lock state, and the received data LD
When A& and reception time information N are given to the CPU 8, the CPU
U8 calculates the position of the positioning device (observation point) from the four relational expressions according to the above-mentioned equation (1). The calculation results are displayed on the display device 17.

[Problem that the invention seeks to solve]

In the positioning device shown in FIG. 4, the first
Initial information such as time and approximate location had to be input via an input device 18 shown by a broken line. In this case, the operation becomes complicated and there is a drawback that an operation for collecting initial information to be input is required.

Second, there is a method in which a backup memory 19 shown by a broken line in FIG. 4 is provided, and initial information is stored in this backup memory 19 and used at the start of operation. However, since the latest information at the start of the operation is not used as the initial information, there is a risk that the positioning operation cannot be started if the information differs significantly.

The present invention has been made in consideration of the above points, and an object of the present invention is to provide a positioning device that can automatically set initial information and shift to normal positioning operation without bothering the operator.

Means for Solving Problem C] In order to achieve the above object, in the present invention, at the start of operation, the CPU 8 sequentially changes the PN signal PNS and the Doppler shift control signal DPd to create a PN lock loop and a Doppler shift lock. The loops are controlled to lock together to receive a signal from one artificial satellite, and initial information is obtained from the received signal DA.

[Effect]

The CPU 8 executes a startup time program at the start of operation. First, the PN signal PNS is generated from the PN signal generation circuit 7, and the VCOI for Doppler shift lock is
The center frequency of O is set and successively changed to lock the PN lock loop and Doppler shift lock loop. When locked, the CPU 8 takes in time information and satellite orbit information from the received signal LDA-iJ- from the demodulation circuit 12 and calculates the approximate position of the observation point. Finally, the CPU 8 takes in the orbit information of all the satellites from the received signal LDA, and then executes a normal operation program.

〔Example〕

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

In addition to the program for performing normal positioning operations, the CPU 8 executes a program shown in FIG. 1 that causes initial information to be set at the start of operation, for example, when the power is turned on.

In step SPI, the CPU 8 provides the first channel data receiving circuit DTR1 with a PN signal PNS and a Doppler shift control signal DPC instructing the center frequency of the Doppler shift locking VCOIO. Next, in step SP2, the CPU 8 determines whether or not the first channel data receiving circuit DTR1 is in a locked state, and if a negative result is obtained, the process returns to step SPI to reapply the PN signal and Doppler shift control signal DPC. .

In order to obtain initial information, it is sufficient to receive one of the signals from the incoming artificial satellites. However, when the power is turned on, it is not possible to identify the satellites that can be received at the observation point.
Also, its location cannot be specified. Therefore, step S
An attempt is made to find and receive a signal from one artificial satellite through PI and step SP2.

As mentioned above, the PN signal differs from satellite to satellite (therefore, there are 18 signals), so the CPU 8 arbitrarily selects the PN signal P.
NS is selected and it is determined whether the correlation with the PN signal of the satellite is established based on the output ENV from the envelope detection circuit 13, and the variable band 1G (1G) of the signal by Doppler shift is determined.
The center frequency of the Doppler shift lock VCOIO is set to one of the 600 (Ilz) intervals considering the C/N (Carrier/No.1se), and the demodulation circuit checks whether a received signal is obtained. 12 output L
Judging from DA. As a result, if a negative result is obtained, the center frequency of the Doppler shift lock VC010 is switched, the judgment is made again, and the operation is repeated. If a signal from a satellite cannot be received for one PN signal even if the center frequency of the Doppler shift locking vCO is switched over the entire Doppler shift variable band, the above operation is performed for other PN signals.

By doing so, a positive result will be obtained in step SP2. When a positive result is obtained, the CPU 8 takes in time information from the received signal LDA in step SP3, and
In step SP4, the orbital information of the satellite is acquired.The position of the satellite can be specified from these time information and orbital information.

Next, in step SP5, the CPU 8 calculates the approximate position of the observation point based on the information, for example, by hyperbolic navigation. Let us assume that the artificial satellite from which the signal was received is referred to as SAT, its orbit as TR shown in FIG. 2, and its positions at three different points in time as Pi, P, 2, and P3. The propagation time of the signal sent out at position P1 (ΔT shown in FIG. 3) and the position P2
From the difference in the propagation time of the signal sent out in , it is considered that the approximate position PR of the observation point is on a hyperboloid of revolution C1 with two points P1 and P2 as focal points. Also, from the difference between the propagation time of the signal transmitted at position P2 and the propagation time of the signal transmitted at position P3, the approximate position PE of the observation point is 2
It is considered to be on a hyperboloid of revolution C2 with focal points at points P2 and P3. Therefore, it is possible to obtain many rotational hyperboloids using information at different times and calculate the approximate position PE as the intersection point.

Thereafter, the CPU 8 acquires orbit information of other artificial satellites from the received signal LDA. Here, the signals from each artificial satellite include not only its own orbit information as described above, but also orbit information about other artificial satellites, although the accuracy is lower.

In this way, the elevation angle of each satellite is calculated from the approximate position of the observation point and the orbit information of each satellite, and the 4
Each channel data receiving circuit D
The process proceeds to a normal operation step SP7 in which four equations (1) are established based on the received signals LDA from the four channel data receiving circuits DTR1 to DTR4 and a positioning calculation is performed.

According to an embodiment implementing the processing sequence of FIG.
Since the initial information necessary for positioning operation is obtained by receiving signals from several artificial satellites, it is possible to improve operability without having to input the initial information again, and it is possible to improve operability by having the initial information stored in advance. It's fine without it.

Note that in the above embodiment, the first channel data receiving circuit D
Although the TRI is used to search for and receive a signal from one artificial satellite, all the channel data receiving circuits DTR1 to DTR4 may be used to search for a signal from one artificial satellite. In this case, the time required from turning on the power to receiving a signal from one artificial satellite can be shortened.

〔Effect of the invention〕

As described above, according to the present invention, the initial information necessary for transitioning to normal operation is obtained by receiving a signal from one artificial satellite, so there is no need to store the initial information in advance. Furthermore, it is possible to obtain a positioning device that does not require new input at the start of operation.

[Brief explanation of drawings]

Figure 1 is a flowchart explaining the operation of the CPU 8 of the positioning device according to the present invention, Figure 2 is a route map explaining hyperbolic navigation used to calculate the approximate position of an observation point, and Figure 3 is the principle of the GPS system. FIG. 4 is a block diagram showing a conventional positioning device, and FIG. 5 is a signal waveform diagram showing envelope detection output in slide mode. 1...Antenna, 4...Local oscillation circuit, 5.11...Band pass filter, 8...
...CPU, 10...VCO113 for Doppler shift lock...Envelope detection circuit,
15... VCo for PN lock, 16...
・Timer, DTR1 to DTR4...1st to 4th
Channel data receiving circuit.

Claims (1)

[Claims] A PN lock loop that maintains this state after obtaining a despread output signal by correlating it with a PN signal included in a received signal consisting of a spread spectrum signal arriving from an artificial satellite, and a PN lock loop that maintains this state after obtaining a despread output signal. A Doppler shift lock loop that corrects the Doppler shift that occurs in the converted input signal obtained by the input signal and demodulates the data by passing it through a narrow band pass filter, and position information and propagation of the satellite contained in the demodulated received signal. time information 4
In the positioning device, the calculation means is configured to switch control signals at the start of operation until both the PN lock loop and the Doppler shift loop are locked. A positioning device characterized in that when a locked state is obtained for one of the artificial satellites, initial information necessary for calculating the position of an observation point is taken in and set.