JPH0640126B2 - Positioning device - Google Patents

Description

The present invention relates to a positioning device, and more particularly to a GPS system (Gl) for positioning using a data signal transmitted from an artificial satellite.
It is suitable to be applied to the obal Positioning System).

[Prior Art] A GPS system receives a data signal such as position information and time information sent from an artificial satellite to the ground at an observation point, and accurately knows the position time and the like of the observation point based on the received data. In the system designed to be able to do so, the i-th artificial satellite SAT _i (where its position is (x _i , y _i , z _i )) and a point P (x ₀ , y ₀ , z ₀ ) on the surface of the earth or in the sky (x _i −x ₀ ) ² + (y _i −y ^{_{0) 2 + (z i -z}} 0) 2 = _[(t i -t ₀₎ ×
c] ² ... (1) It is based on the principle that the position and time of the observation point P can be known by obtaining the unknown number by calculation.

Here t _i is the time that the data signal from the satellite is transmitted, t _o is the time that has received the data signal at the observation point P, c is the speed of light.

In order to solve the equation (1), it is necessary to formulate the equation by the unknown number. In order to actually observe the unknown number of artificial satellites at the observation point P at the same time, a large number, for example, 1
Eight satellites are planned to orbit the earth, thus formulating the necessary formulas based on the data from each satellite.

For example, when the GPS system is used as the positioning system, the error components included in the four unknowns x ₀ , y ₀ , z ₀ , and t ₀ are based on the data transmitted from the artificial satellite in the positioning device shown in FIG. Calculate and position P
It is considered to obtain (x ₀ , y ₀ , z ₀ ).

The positioning device shown in FIG. 4 receives the first to fourth channel data for solving four unknowns, that is, the positions (x ₀ , y ₀ , z ₀ ) of the observation point and the error component included in the reception time t ₀ of the data. It has circuits DTR1 to DTR4.

In the GPS system, the artificial satellites use carrier waves of frequencies 1.57542 [GHz] and 1.2276 [GHz] belonging to L band, P code of clock frequency 10.23 [MHz] and 1.0.
A spectrum-spread signal is transmitted using a C / A code of 23 [MHz].

Here, the P code and C / A code are 1023 [chips / m
[s] pseudo noise signal (this is called a PN signal),
The data is 50 [bps] BPSK (binary phase shi
ft keying) signal is converted into P code and C / A code and transmitted.

Thus, the data transmitted from each satellite includes the orbital data of that satellite, the orbital data of other satellites that are orbiting the Earth, and the highly stable atomic clock (which is called the satellite clock) mounted on the artificial satellite. The time data determined by a satellite clock, which is sent at a predetermined time interval (that is, every 6 seconds) together with the deviation data between the time system (which is referred to as a satellite time system) and the world standard time.

In the case of the positioning device shown in FIG. 4, the carrier frequency is 1.57542 [GH
The signal [z] is received by the antenna 1 and converted into the first intermediate frequency signal IF ₁ having a frequency of 75.42 [MHz] by the frequency conversion circuit 2 and then given to the post-multiplication circuit 3. The frequency generated by the local oscillation circuit 4 is 64.72 [MH
z] frequency output LO ₁ is applied, and the second intermediate frequency signal IF ₂ of frequency 10.7 [MHz] obtained at the output terminal is passed through the band pass filter 5 having a relatively wide pass band to the first to fourth channel data. Receiver circuits DTR1 to DTR
4 to the second multiplication circuit 6.

Here, the first to fourth channel data receiving circuits DTR1 to
The DTR 4 is capable of forming four equations based on the above equation (1) by receiving data from four satellites respectively. Each receiving circuit DTR
1 to DTR4 have the same configuration as each other, and accordingly
The structure of the channel receiving circuit DTR1 will be described.

The second multiplication circuit 6 converts the spread spectrum data signal transmitted from the satellite into the PN signal PNS generated from the PN signal generation circuit 7 into the second intermediate frequency signal IF ₂
The despreading processing is performed by multiplying by 1023 [chip / ms] like the C / A code included in the second intermediate frequency signal IF ₂ as the PN signal.
It consists of the code signal of.

Here, a C / A code of a unique binary pattern is assigned to each satellite, and the PN signal generating circuit 7
Is capable of selectively generating the PN signal PNS having the C / A code pattern assigned to all satellites (for example, 18 satellites) under the control of the CPU 8.

Thus, the phase of the PN signal included in the second intermediate frequency signal IF ₂ is PN generated by the PN signal generating circuit 7.
When the correlation with the signal PNS is obtained, the despread output signal DKN having a high signal level is obtained at the output end of the multiplication circuit 6, and this is given to the third multiplication circuit 9.

The output S1 of the Doppler shift lock voltage controlled oscillator (VCO) 10 is applied to the multiplication circuit 9, and the phase shift keying signal PSS of frequency 455 [KHz] is sent to the output terminal. This phase shift keying signal PSS is given to a band pass filter 11 having a narrow pass band (for example, about ± 1 [KHz]) and the despread output signal DKN obtained when the correlation is obtained is demodulated by a Costas loop, for example. It is given to the circuit 12. As a result, the reception data LDA of 50 [bps] is output to the output terminal of the demodulation circuit 12.
Are demodulated and obtained and sent to the CPU 8.

The CPU 8 reproduces the carrier based on the received data LDA to change the relative position between the orbit of the satellite and the positioning device, or the relative deviation between the carrier frequency of the satellite and the oscillation frequency of the local oscillation circuit 4. According to the change, the Doppler shift control signal DPC is applied to the Doppler shift lock VCO 10 to control its oscillation frequency. Thus, even if the center frequency of the received signal is shifted by the Doppler effect, the phase shift keying signal PSS The frequency can be controlled to about 455 [kHz]. Thus, the demodulation circuit 12-CPU 8-VCO 10-multiplication circuit 9 forms a Doppler shift lock loop.

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 its detection output ENV is sent to the VCO 15 for PN lock through the low pass filter 14 to the oscillation frequency control signal CO.
Given as NT.

The PN lock VCO 15 has a first oscillation circuit whose oscillation frequency changes in accordance with a change in the control signal CONT and a second oscillation circuit which oscillates at a predetermined frequency.
When the slide mode signal SLID is given from the PU 8, the oscillation frequency output S2 of a predetermined frequency is given to the PN signal generating circuit 7 by using the second oscillating 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 PN
An operation mode is obtained in which the phase of the signal PNS continuously shifts 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 the correlation between S and the PN signal included in the received signal is obtained, a peak waveform that rises in a triangular wave shape is exhibited, and the signal level becomes small in the other intervals where there is no correlation.

The CPU 8 crosses the threshold value L when the envelope detection signal ENV rises to the peak value.
_When the envelope detection signal ENV has _th and the envelope detection signal ENV does not exceed the threshold level L _th , the slide mode signal SLID is applied to the PN lock VCO 15 to maintain the slide mode state. On the other hand, when the envelope detection signal ENV exceeds the threshold level L _th , the slide mode signal SLID disappears.

In this way, the phase of the PN signal PNS is controlled so as to follow the phase of the PN signal contained in the received signal, thus maintaining a correlated state. As a result, the envelope detection circuit 13-the low-pass filter 14 and the CPU 8-PN VCO 15-PN for the lock
A PN lock loop is formed by the loop of the signal generating circuit 7 and the multiplying circuit 6.

In addition to this, the positioning device has a timer 16 and measures the time when the positioning device receives a signal from a satellite. The timer 16 is a predetermined time (for example, 1
The reset signal PPS given every [s]) is received and reset, counted by the clock signal CK coming every predetermined time (for example, 20 [ns]), and the PN signal generation circuit 7 gives the epoch signal EP. At this time, the count value N representing the reception time information is sent to the CPU 8 to calculate the propagation time.

In the configuration shown in FIG. 4, when all of the first to fourth channel data receiving circuits DTR1 to DTR4 are in the lock state and the received data LDA and the reception time information N are given to the CPU8, the CPU8 causes the above-mentioned (1). The position of the positioning device (observation point) is calculated from four relational expressions according to the formula. The calculation result is displayed on the display device 17.

[Problems to be solved by the invention]

In the positioning apparatus shown in FIG. 4, the first PN lock loop and the Doppler shift lock loop are brought into the lock state when the positioning operation is started, for example, when the power is turned on.
In addition, it is necessary to input initial information such as time and approximate position via the input device 18 indicated by a broken line. In this case, there are disadvantages that the operation becomes complicated and the operation of collecting the input initial information is required.

Secondly, 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 the backup memory 19 to be used at the time of starting the operation. However, since the latest information at the start of the operation is not used as the initial information, there is a possibility that the positioning operation cannot be started when the information is significantly different.

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 capable of automatically setting initial information and shifting to a normal positioning operation without bothering an operator.

[Means for solving problems]

In order to achieve such an object, in the present invention, the CPU 8 controls the PN signal PNS and the Doppler shift control signal DPC sequentially at the start of operation to control both the PN lock loop and the Doppler shift lock loop to lock them. It receives a signal from an artificial satellite and tries to obtain initial information from the received signal LDA.

[Action]

The CPU 8 executes the program of the start time at the start of the operation. First, a PN signal PNS is generated from the PN signal generating circuit 7, and a VCO1 for Doppler shift lock is generated.
A center frequency of 0 is set and is sequentially changed to lock the PN lock loop and the Doppler shift lock loop. When locked, the CPU 8 fetches the time information and the satellite orbit information from the received signal LDA from the demodulation circuit 12 and calculates the approximate position of the observation point. Finally C
The PU 8 takes in the orbit information of all artificial 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. CPU
Reference numeral 8 is a program for setting initial information at the start of operation, for example, at power-on, in addition to a program for performing normal positioning operation.
Run the program shown.

In step SP1, the CPU 8 supplies the first channel data receiving circuit DTR1 with the PN signal PNS and the Doppler shift control signal DPC indicating the center frequency of the Doppler shift lock VCO 10. Next, in step SP2, the CPU 8 determines whether or not the first channel data receiving circuit DTR1 is in the lock state, and when a negative result is obtained, the CPU 8 returns to step SP1 and reapplies the PN signal and the Doppler shift control signal DPC. .

To obtain the initial information, it is sufficient to receive one of the signals from the incoming satellites. However, when the power is turned on, the satellite that can be received at the observation point side cannot be specified,
In addition, its position cannot be specified. Therefore, step SP
1 and the signal of one artificial satellite is searched for and received through step SP2.

Since the PN signal is different for each artificial satellite as described above (therefore, 18 signals exist), the CPU 8 arbitrarily selects the PN signal PNS to determine from the envelope detection circuit 13 whether the PN signal of the artificial satellite is obtained. Of the output signal ENV and the variable band of the signal due to Doppler shift 10
[KHz] is approximately 6 considering C / N (Carrier / Noise)
The center frequency of the VCO 10 for Doppler shift lock is set to one of the divisions every 00 [Hz], and it is judged from the output LDA of the demodulation circuit 12 whether the received signal is obtained. As a result, when a negative result is obtained, the central frequency of the VCO 10 for Doppler shift lock is switched, the judgment is made again, and the operation is repeated. For one PN signal, if the center frequency of the VCO for the Doppler shift lock is switched over the entire Doppler shift variable band and the signal from the artificial satellite cannot be received, the above operation is performed for the other PN signals. .

By doing so, an affirmative result is eventually obtained at step SP2. When a positive result is obtained, the CPU 8 fetches the time information from the received signal LDA in step SP3,
At step SP4, the orbit information of the satellite is fetched. The position of the satellite can be specified from the time information and the orbit information.

Next, in step SP5, the CPU 8 calculates the approximate position of the observation point by hyperbolic navigation based on the information. Let's assume that the artificial satellite from which the signal was received is SAT _i ,
The trajectory is TR shown in FIG. 2, and the positions at three different time points are P1, P2, and P3. The propagation time of the signal transmitted at the position P1 (ΔT shown in FIG. 3) and the position P2
It is considered that the approximate position PE of the observation point is on the rotating hyperboloid C1 having the two points P1 and P2 as the focal points from the difference with the propagation time of the signal transmitted at. Further, the approximate position PE of the observation point is 2 from the difference between the propagation time of the signal transmitted at the position P2 and the propagation time of the signal transmitted at the position P3.
It is considered to be on the rotating hyperboloid C2 having the points P2 and P3 as the focal points. Therefore, more rotational hyperboloids can be obtained from the information at different times, and the approximate position PE can be calculated as the intersection.

After that, the CPU 8 fetches orbit information of other artificial satellites from the received signal LDA. Here, the signals from the artificial satellites include the orbital information of the artificial satellites as described above and the orbital information of other artificial satellites although the accuracy is lowered.

Thus, the elevation angle of each artificial satellite is calculated from the approximate position of the observation point and the orbit information of each artificial satellite, and the
Select each satellite and select each channel data receiving circuit D
The operation is assigned to TR1 to DTR4, and based on the received signals LDA from the four channel data receiving circuits DTR1 to DTR4, the above described four equations (1) are set up and the operation proceeds to the normal operation step SP7.

According to the embodiment for executing the processing sequence of FIG.
Since the signal from each artificial satellite is received to obtain the initial information necessary for the positioning operation, it is possible to improve the operability without inputting the initial information again, and to have the initial information in advance. You don't have to.

In the above embodiment, the first channel data receiving circuit D
Although the signal from one artificial satellite is searched and received by using TR1, the signal from one artificial satellite may be searched by using all the channel data receiving circuits DTR1 to DTR4. In this case, it is possible to shorten the time required from turning on the power to receiving a signal from one artificial satellite.

〔The invention's effect〕

As described above, according to the present invention, the initial information necessary for shifting to the normal operation is obtained by receiving the signal from one artificial satellite, so that it is necessary to store the initial information in advance. It is possible to obtain a positioning device that does not have to be input again at the start of operation.

[Brief description of drawings]

FIG. 1 is a flow chart for explaining the operation of the CPU 8 of the positioning device according to the present invention, FIG. 2 is a schematic diagram for explaining the hyperbolic navigation used to calculate the approximate position of the observation point, and FIG. 3 is a GPS system. FIG. 4 is a block diagram showing a positioning device which has been conventionally considered, and FIG. 5 is a signal waveform diagram showing an envelope detection output in the slide mode. 1 ... Antenna, 4 ... Local oscillation circuit, 5, 11 ... Bandpass filter, 8 ... CPU, 10 ... VCO for Doppler shift lock, 13 ... Envelope detection circuit, 15 ... VCO for PN lock , 16 ... Timer, D
TR1 to DTR4 ... First to fourth channel data receiving circuits.

Claims (1)

[Claims] 1. A PN lock loop which maintains this state after obtaining a despread output signal by correlating with a PN signal included in a received signal which is a spread spectrum signal coming from an artificial satellite, and said despreading. A Doppler shift lock loop for correcting a Doppler shift occurring in a signal obtained based on an output signal and demodulating the received signal, and an orbit of the artificial satellite included in the received signal demodulated for a predetermined number of the artificial satellites. In a positioning device comprising a calculation means for calculating the position of an observation point based on information and time information, the calculation means has both the PN lock loop and the Doppler shift lock loop for one artificial satellite at the start of operation. When the state is reached, the position of the artificial satellite and the position of the artificial satellite are determined based on the information included in the demodulated received signal. Means for calculating the approximate position of the observation point by calculating the signal propagation time up to the measurement point multiple times at different times, and selecting a predetermined number of artificial satellites from the artificial satellites that can be received at this approximate position And a means for calculating the position of the observation point.