JPH071303B2 - Positioning device - Google Patents

Description

The present invention relates to a positioning device, and more particularly to a GPS system (Globa) for positioning using a data signal transmitted from an artificial satellite.
l Positioning System).

[Background technology and its problems]

The GPS system receives data signals such as position information and time information sent from the satellite to the ground at the observation point, and can accurately know the position, time, etc. of the observation point based on the received data. In the system planned for, the i-th artificial satellite SAT _i (its position is (x _i , y _i , z _i ) And) and a point P on the surface of the earth or in the sky
_{(X o, y o, z} o) holds the formula (x _i -x _o) with respect to the distance between the ^{_{2 + (y i -y o)}} 2 + (z i -z o) 2 = [[t _i −t _o ) × c] ² …… Based on (1), it is possible to know the position and time of the observation point P by calculating the unknowns x _o , y _o , z _o , t _o by calculation. It is a principle.

Where t _i is the time when the data signal was transmitted from the satellite,
t _o is the time when this data signal was received 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 fact, in order to simultaneously observe the unknown number of artificial satellites at the observation point P, a large number, for example, 18
Individual satellites are planned to orbit the earth,
Thus, the necessary formula is created based on the data from each satellite.

For example, when the GPS system is used as a positioning system, four unknowns x _o , y _o , z _o , t _o are calculated based on the data transmitted from the artificial satellite in the positioning device shown in FIG. It is considered to find (x _o , y _o , z _o ).

The positioning device of FIG. 3 is the first for solving four unknowns, that is, the position (x _o , y _o , z _o ) of the observation point and the reception time t _{o of the} data.
-Has fourth channel data receiving circuits DTR1-DTR4.

In the GPS system, artificial satellites use carrier waves of frequencies 1.57542 [GHz] and 1.2276 [GHz] belonging to the L band, P code of clock frequency 10.23 [MHz] and 1.023 [MH].
z] C / A code is used to transmit the spread spectrum signal.

Here, the P code and C / A code are pseudo-noise signals of 1023 [chips / ms] (this is called PN signal), and the data is 50
Set the [bps] BPSK (binary phase shift keying) signal to P
It is converted and transmitted by the code and C / A code.

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. 3, the carrier frequency is 1.57542 [GHz]
Signal is received by the antenna 1 and the frequency conversion circuit 2
At the frequency of 75.42 [MHz], the first intermediate frequency signal IF ₁ is converted to the first intermediate frequency signal IF ₁ which is then applied to the multiplication circuit 3. The frequency output LO _{1 of} the frequency 64.72 [MHz] generated in the local oscillation circuit 4 is given to the multiplication circuit 3, and the frequency 10.
Providing through the second intermediate frequency signal IF ₂ is bandpass filter 5 having a relatively wide pass band of 7 [MHz] to the second multiplying circuit 6 of the first to fourth channel data receiving circuit DTR1～DTR4.

Here, the first to fourth channel data receiving circuits DTR1 to DTR4
By receiving the data from each of the four satellites, the four equations can be created based on the above equation (1). The receiving circuits DTR1 to DTR4 have the same configuration as each other, and therefore the configuration will be described below by using the receiving circuit DTR1 of the first channel.

This second multiplication circuit 6 reverses by multiplying the spread spectrum data signal transmitted from the satellite by the PN signal PNS generated by the PN signal generation circuit 7 with the second intermediate frequency signal IF ₂ . The spread processing is performed, and the PN signal PNS is a code signal of 1023 [chips / ms] like the C / A code included as a PN signal in the second intermediate frequency signal IF ₂ .

Here, each satellite has a unique binary pattern
The C / A code is assigned, and the PN signal generation circuit 7 selectively selects 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. It is designed to be able to occur.

Thus, the phase of the PN signal included in the second intermediate frequency signal IF ₂ is the PN signal PNS generated by the PN signal generating circuit 7.
When the correlation is obtained, the despread output signal DKN having 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 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 transmitted to the output end. This phase shift keying signal PSS is applied 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, for example, a Costas loop. Feed to circuit 12. As a result, 50 at the output terminal of the demodulation circuit 12.
The received data LDA of [bps] is 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 satellite orbit and the positioning device, or the relative deviation between the carrier frequency of the satellite and the oscillation frequency of the local oscillator circuit 4. The oscillation frequency of the VC010 for Doppler shift lock is controlled accordingly, and even if the center frequency of the received signal is shifted by the Doppler effect, the frequency of the phase shift keying signal PSS is almost 455
Be able to control to [kHz]. Thus demodulation circuit 12
-CPU8-VCO10-The 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 bandpass filter 11 is given to the envelope detection circuit 13, and its detection output ENV is passed through the lowpass filter 14 to the PN
It is given to the lock VCO 15 as the oscillation frequency control signal CONT.

The PN lock VCO 15 has a first oscillation circuit whose oscillation frequency changes according to the change of the control signal CONT, and also has a second oscillation circuit which oscillates at a predetermined frequency. Then, the oscillating frequency output S2 having a predetermined frequency is applied 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 the phase of the PN signal PNS continuously changes with respect to the PN signal included in the received signal. An operation mode in which the phases are shifted can be obtained. At this time, the envelope detection output ENV of the envelope detection circuit 13 is P as shown in FIG.
When the correlation between the N signal PNS and the PN signal contained 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 CPU8 has a threshold level L _th that crosses the envelope detection signal ENV when it rises to the peak value, and a slide mode signal when the envelope detection signal ENV does not exceed this threshold level L _th. SLID
To the VCO 15 for PN lock to maintain this 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-low-pass filter 14 and
A PN lock loop is formed by a loop of the CPU 8-PN lock VCO 15-PN signal generation circuit 7-multiplication 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 receives a reset signal PPS given every predetermined time (for example, 1 [S]) from a clock mounted on the positioning device (this is called a user clock) and resets, and at every predetermined time (for example, 20 [ns]) Clock signal arriving at
Counting is performed by CK, and when an epoch signal EP is given from the PN signal generating circuit 7, a count value N representing signal time information is sent to the CPU 8 to calculate a propagation time.

In the configuration of FIG. 3, when all of the first to fourth channel data receiving circuits DTR1 to DTR4 are in the locked state and the received data LDA and the received time information N are given to the CPU 8, C
The PU 8 calculates the position of the positioning device (observation point) from the four relational expressions according to the above-mentioned expression (1). The calculation result is displayed on the display device.
Displayed by 17.

However, according to the apparatus shown in FIG. 3, since only four channel data receiving circuits are provided, if any channel data receiving circuit is not in the lock state, four equations based on the equation (1) are used. However, there was a drawback that it was not possible to locate the position. For example, when an airplane equipped with this positioning device makes a sharp turn, the Doppler shift fluctuates greatly, and the lock state of the channel 1 and 2 data reception circuits is released, and positioning cannot be performed for a while after that.

Further, in practice, the resolution of the counter 16 is selected to be, for example, about 20 [ns]. Therefore, in principle, the error must be included. An error is included in the value obtained by solving the four unknowns.

[Object of the Invention]

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 enhancing positioning accuracy and performing positioning without interruption.

[Outline of Invention]

In order to achieve such an object, in the present invention, the number of channel data receiving circuits provided is larger than the unknown number in the positioning calculation, positioning can be performed using more information, and the positioning operation is actually continued even if the amount of information is slightly reduced. To be able to.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG. 1 in which parts corresponding to those in FIG. In this positioning device, six channel data receiving circuits DTR1 ~
DTR6 is provided, the received data LD from the satellite to comply with these channel data receiving circuit DTR1~DTR6 the PN signal assigned to input second intermediate frequency signal IF ₂ respectively
The A and the reception time information N are sent to the CPU 8.

The positioning device of FIG. 1 executes the processing sequence of FIG. The CPU8 calculates the elevation angle of each artificial satellite by using the orbital data and the like stored in the internal memory in step SP1, and proceeds to the next step SP2 to obtain the PN signal PNS assigned to the satellites whose elevation angle is 5 degrees or more. It is selected and assigned to the PN signal generating circuit 7 of each channel data receiving circuit DTR1 to DTR6. Here, the elevation angle is calculated in order to detect artificial satellites that are orbiting above the horizon and horizon and whose signals contain as little error as possible due to the ionosphere, etc. If there are more than 6 in descending order of elevation angle
Select one and assign PNS.

Next, the CPU 8 calculates the Doppler shift of the artificial satellite assigned in step SP3, and sends a control signal to the VCO 10 for Doppler shift lock to control it.

After that, in step SP4, it is determined whether or not any four or more channel data receiving circuits are in the lock state. If a negative result is obtained, the process returns to step SP2 and the four or more channel data receiving circuits are in the lock state. Repeat steps SP2 to SP4 until. On the other hand, when a positive result is obtained in step SP4, the CPU 8 causes the position information (x _i , y _i , z _i ) of each satellite SAT _i corresponding to each channel data receiving circuit locked in step PS5.
Is obtained from the orbit information of the satellite included in the reception data LDA, and the reception time information N is fetched from the timer 16.

After that, the CPU 8 calculates the above equation (1) for each channel data receiving circuit in step SP6 and minimizes the influence of the error contained in the calculation result, for example, the position of the observation point by the least square approximation method. Find P (x _o , y _o , z _o ). The obtained value is converted into, for example, north latitude, east longitude, and altitude and displayed on the display device 17 at step SP7.

After this display, return to the above-mentioned step SP4, and if the lock state is maintained for four or more channel data receiving circuits, take the satellite orbit information and time information at the next timing (step SP5). The position of the observation point is measured in the same manner as described above. This positioning operation (step SP4
Up to SP7), most of the six channel data receiving circuits DTR1 to DTR6 are in the lock state during the most of the repetition time, and the calculation based on the above equation (1) is executed.

In addition, in the GPS system, it is always 6 ~ at any observation point.
Orbiting the satellites so that eight satellites can be seen.

If the lock state in three or more channel data receiving circuits is released while repeating the positioning operation, a negative result is obtained in step SP4 and the process returns to the initial step SP2.
However, in practice, the six channel data receiving circuits DT are used for most of the time when the positioning operation (steps SP4 to SP7) is repeated.
Since R1 to DTR6 are both in the lock state, even if an airplane or the like equipped with this positioning device makes a sharp turn, for example, the channel data receiving circuit that is out of the lock state is only 1-2.
There are only a few, and it is extremely rare that a negative result will occur at step SP4.

As described above, according to the positioning device of FIG. 1, six channel data receiving circuits are provided, and six relational expressions can be used to solve four unknowns including the parameter for specifying the position. The error included in the result can be reduced. That is, the positioning accuracy can be improved. Further, even if the reception data LDA is not obtained from the channel data receiving circuits 1 and 2 due to the Doppler shift, positioning can be performed using the reception data from the other channel data receiving circuits, so that the positioning operation is stable. It can be performed.

In the above embodiment, the embodiment in which six channel data receiving circuits are provided has been shown, but the present invention is not limited to this, and it is sufficient if there are five or more.

〔The invention's effect〕

As described above, according to the present invention, by providing the number of channel data receiving circuits larger than the unknown number, the positioning accuracy can be improved and the positioning operation can be stably performed even when some information is lost. It is possible to easily obtain a positioning device capable of performing.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a positioning device according to the present invention, FIG. 2 is a schematic diagram showing the principle of a GPS system, and FIG.
FIG. 4 is a block diagram showing a conventional positioning device, FIG. 4 is a signal waveform diagram showing the envelope detection output in the slide mode, and FIG. 5 is a flow chart for explaining the operation of the CPU 8. 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, DTR1 to DTR6 ... First to sixth
Channel data receiving circuit.

Claims (1)

[Claims] 1. A positioning device having a channel data receiving circuit for receiving orbit information and time information of satellites coming from different artificial satellites, and calculating the position of an observation point based on the received orbit information and time information. In the above, at least 5 channels of the channel data receiving circuits are provided, and when the channel data receiving circuits of 5 channels or more are locked, orbit information and time information obtained from the channel data receiving circuits of 5 channels or more, respectively. A positioning device that calculates the position of an observation point so as to reduce the error by five or more relational expressions using