JPS63269080A - Position measuring system - Google Patents

Abstract

PURPOSE:To enable detection of the position of a moving body carrying a relay without using a wide frequency, by transmitting a clock signal as code signal of a spectrum diffusion signal received with the relay to a receiving station. CONSTITUTION:Distance measuring signals PDT of satellites are passed through a delay circuit 13, a multiplication circuit 12 and a filter circuit 14 of a relay 4 to obtain clock signals CK1-CK4 as C/A code signal. The signals CK1-CK4 are converted into a specified relay signal S1 through a frequency conversion circuit 15 and then, sent to a receiving station 20 through an antenna 17. At the receiving station 20, the signal S1 is demodulated into the signals CK1-CK4 through a frequency conversion circuit 31 and a filter circuit 32 and then, inputted into a phase difference detection circuit 33, which can calculate the position of a moving body based on phase differences between the signals CK1-CK4. With such an arrangement, the position of the moving body can be computed without using a wide frequency band by calculating the position thereof based on changes in the phase difference of the clock signals.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Industrial field of application B. Outline of the invention C. Conventional technology Problems to be solved by the invention E. Means for solving the problems (Figs. 1, 2, and 5) F. Effects (Fig. 1) 2 and 5) G Embodiment (FIGS. 1 to 5) H Effect of the invention
bal positioning 5yste+++)
This is suitable for application to a position measurement system using the system.

B. Summary of the Invention The present invention provides a method for transmitting a signal in a narrow frequency band to a receiving station in a position measuring system by transmitting a clock signal of a code signal used for spectrum spreading of a ranging signal from a relay device to the receiving station. Then, the position of the relay device can be calculated.

C. Prior Art Conventionally, a GPS system has been known as a system that measures the position of a moving object such as an aircraft, a ship, a vehicle, etc. moving on the ground, sea, or air from moment to moment. This GPS system uses a plurality of satellites, for example, four, as a ranging signal source, and receives the orbit information and clock information of each satellite from the ranging signal, which is a spread spectrum signal propagated from each satellite. By knowing the propagation time of the ranging signal between the satellite and the moving object whose position is to be measured, it is possible to calculate the position of the moving object.

Using the GPS system with these characteristics,
If the position of a mobile object moving within a designated controlled area on the sea or in the air could be measured in real time using a receiving station installed at a designated location on the earth as a ground station, it would be possible to use it for various purposes. It is thought that the GPS system can be applied.

One way to achieve this is to mount a GPS receiver on a moving object, which serves as a ranging signal receiver that can measure the position based on the above principle, and the position changes from moment to moment as the moving object moves. It may be possible to calculate the position on the moving body and transmit the calculation result to the receiving station through a transmission path separately provided between the mobile body and the receiving station.

However, it is inevitable that a ranging signal receiver will be relatively complex and large. Therefore, if a ranging signal receiver is mounted on a moving object, the structure of the entire moving object will become complicated and large. It is inevitable that it will be expensive.

Therefore, in practical terms, there is a problem in that the GPS system cannot be applied to small and inexpensive moving objects.

One method to solve this problem is to convert the ranging signal received by a mobile object to a predetermined frequency and transmit it to a receiving station, and the receiving station calculates the position of the mobile object by relaying a spread spectrum signal. A system has been proposed (Japanese Patent Application No. 78083/1983).

D Problems to be Solved by the Invention However, the spread spectrum signal used in this GPS system has an excellent feature in that highly confidential communication can be achieved by using a pseudo-noise (PN) code signal. In principle, it is impossible to avoid expanding the band required for spread spectrum, for example, the carrier frequency is 1575.42 (MHz) or 1227.
6 (MHz), respectively P (precis
ion) When calculating the position using a pseudo-noise code signal consisting of a code signal, the sideband is ±10.23
It is necessary to receive signals in the (MHz) frequency band. On the other hand, C/A (clear/acquisi
When calculating a position using a pseudo-noise code signal consisting of a tion) code signal, it is necessary to receive a signal in the main frequency band of 1°023 (MHz) as a sideband.

Therefore, when frequency converting and relaying such spread spectrum signals, it is necessary to secure a wide frequency band for relaying, and in frequency bands where the occupied bandwidth is subject to strict regulations, it is difficult for the GPS system to There is a problem that the ranging signal cannot be relayed.

The present invention has been made in consideration of the above points, and aims to propose a position measurement system that allows a receiving station to calculate the position of a mobile object without using a wide frequency band for relaying. It is.

E Means for Solving the Problem In order to solve this problem, the present invention provides distance measurement signals that are spread spectrum with a predetermined code signal and transmitted from a plurality of signal generation sources IA, IB, IC, and ID. Based on the signals PDTI, PDT2, PDT3, PDT4, ranging signals PDTI, PDT2, PDT3, PDT4
In a position measurement system configured to calculate the reception position of distance measurement signals PDTI, PDT2, PDT3, P
D, T4 is received, and the code signal clock signal CKI,
Obtain CK2, CK3, CK4, clock signals CK1, C
The relay device 4 transmits K2, CK3, and CK4, and the clock signal C transmitted from the relay device 4 has 1, CR2, and CR.
2. Receive CR2, clock signals CKI, CR2, C
The receiving station 20 calculates the receiving position of the relay device 4 based on the phase difference between R2 and CR2.

Clock signal CK1, C of the code signal at the 2-action receiving position
If the phase difference between R2, CR2, and CR2 is known, the reception position can be determined based on the change.

Therefore, in the relay device 4, the received distance measurement signal PDT1
．． ．． Clock signals CKI, CK2, and C of code signals required for spectrum spreading of PDT2, PDT3, and PDT4
By obtaining R2 and CR2 and transmitting them to the receiving station 20, clock signals CKI and CK2 can be obtained in a narrow frequency band.
, CR2, and CR2, and the position of the relay device 4 can be calculated at the receiving station 20.

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

In Figure 1, IA, IB, IC, and ID are satellites of the GPS system, and each satellite IA-ID has information such as orbit information and clock information, and Doppler shift occurs as each satellite IA-ID moves. , the center frequency is 1575.42 (MHz) ± 5 (kHz) and 1
Transmits a ranging signal that fluctuates in the range of 227.6 (MHz) ± 5 (k, Hz).

The mobile object 2 is provided with a relay device 4 as shown in FIG. 2, and the center frequency of the ranging signals transmitted from the satellites IA to ID is 1575.42 (MHz) ±5 [kHz).
Distance measurement signal PDT (PDTI, PDT2, PDT3,
PDT4), and provides the distance measurement signal PDT to the multiplication circuit 12 and also provides it to the multiplication circuit 12 via the delay circuit 13.

Therefore, via the multiplication circuit 12, a signal SM multiplied by the delayed signal DPDT of the distance measurement signal PDT and the distance measurement signal PDT is obtained.

Here, each distance measurement signal PDT has a frequency of 1575.42 (
P S K (p
haseshift keying) and then spread spectrum with a pseudo-noise code signal consisting of a P code and a C/A code.
Expressing the distance measurement signal PDTI from the following equation 3%), 5in(ω.t+φ) on the right side of equation (1) represents the carrier wave signal, and A(t) represents the carrier wave signal 5in(ω.t+
represents a modulation signal sequence for φ).

Furthermore, the value of A(t) is expressed as the value of the following formula % formula (3) with respect to the value of the C/A code signal, and the distance measurement signal PDTI is It can be seen that the phase of is changed by 180''.

On the other hand, if the delay time of the delay circuit 13 is expressed by the value τ, then
The delayed signal DPDTI of the ranging signal PDTI transmitted from the satellite IA out of the delayed signal DPDT can be expressed by the following formula % formula % ().
Regarding the distance measurement signal PDTI, it is possible to obtain a multiplication signal SMI expressed by the following equation (3).

Here, the delay time τ of the delay circuit 13 is determined by each distance measurement signal PDTf.
7) For the carrier signal frequency 1575.42 (MHz), if the value of the following formula % is selected, the following formula sin (ωo(-τ) + φ) = sin(ω, 1+
φ)...(8) can be obtained, and by substituting this into equation (5),
The following formula % formula %) This means that the first right-hand side of (9)
This means that a signal component of the pseudo-noise code signal expressed by the second term and a spread spectrum signal consisting of a frequency component twice that of the ranging signal PDTI expressed by the second term are obtained.

Further, in each of the satellites IA to ID, a carrier wave signal is created by multiplying the clock signal of the C/A code signal by 1540 times.

Therefore, in equation (7), the delay time τ of the delay circuit 13 is 1/2 n=770 for the carrier signal multiplication ratio 1540.
By setting the time expressed by (approximately 0.5 (#sec)), the signal component expressed by formula A(t) becomes
There is a delay of 1/2 clock period with respect to one clock period MT of the C/A code signal.

As a result, as shown in FIG. 3, the multiplication signal 5Ml0 formula A (
In the signal component represented by t)・A (−τ), the C/A code signal 5CAI (Fig. 3 (A)) included in the signal component represented by the formula A(t), The C/A code signal 5CAt (Fig. 3 (B )), a multiplication signal 5cA (FIG. 3(C)) is obtained.

The filter circuit 14 is a narrow-band bandpass filter circuit whose center frequency is set to a value equal to the clock frequency of 1.023 (MHz) of the C/A code signal, and converts the multiplication signal SMI to the 3i! The overband signal components are extracted and output to the frequency conversion circuit 15.

As a result, the multiplication signal 5Ml0 is transmitted through the filter circuit 14.
From the signal component expressed by the formula A(t)・A(−τ), C/
Clock signal CK1 of A code signal 5CAI can be extracted.

Similarly, ranging signals PDT obtained from other satellites IB to ID
2 to PDT3, the multiplication signal SM2.3M is also applied to each ranging signal PDT2 to PDT3 via the multiplication circuit 12.
3. SM4 is obtained, and thus the ranging signal PDTI~ transmitted from each satellite MIA~ID via the filter circuit 14
Clock signals CKI to CK4 of the C/A code signal used for spectrum spreading of PDT4 can be obtained.

In this way, the delay circuit 13 and the multiplication circuit 12 have a delay time of 1/2 clock period and a C circuit having the same configuration as the delay detection circuit.
/A code signal clock signal demodulation circuit is configured.

The frequency conversion circuit 15 converts the frequency of the clock signals CKI to CK4 to, for example, a center frequency of 500 [MHz].
, and transmits the relay signal S1 to the receiving station 20 via the adding circuit 16 and the antenna 17.

Here, as shown in FIG. 4, when the mobile object 2 moves on the ground surface f from the point P1 to P2 in the direction from the satellite IB to the satellite IA, the distance from the satellite IB to the mobile object 2 changes accordingly. The distance from i%1RB1 increases to distance RB2, and conversely, the distance from satellite IA to mobile object 2 increases from distance RAI to distance RA.
It will be shortened to 2.

Therefore, as the distance from the mobile object 2 to the satellites IA and IB changes, the difference in propagation time between the ranging signals PDTI and PDT2 changes, and accordingly
The phase difference of K2 begins to change.

As described above, when the phase difference between the clock signals CKI and GK2 changes, the distance traveled by the mobile object 2 on the ground surface in the direction of the satellite NIB and IA can be determined based on this change.

Furthermore, including other clock signals CK3 and CK4,
By determining the change in phase difference between each of the clock signals CKI to CK4, the moving distance and moving direction of the moving body 2 within a predetermined region can be determined.

The distance measurement signal PDT actually transmitted from the satellites IA to ID
In I to PDT4, the center frequency changes slightly due to Doppler shift.

Therefore, in each of the clock signals CKI to CK4 obtained via the filter circuit 14, the distance measurement signals PDTI to
The frequency varies slightly with the variation of the center frequency of PDT4, and according to measurements, each clock signal CKI~CK4
have different frequencies within a range of approximately ±2 (Hz).

Therefore, based on this frequency difference, each clock signal C
Detects K1 to CK4 and outputs each clock signal CKI to CK4.
By detecting changes in the phase difference between them, the moving distance and moving direction of the moving body 2 can be determined.

Incidentally, in order to transmit the clock signals CKI to CK4 to the receiving station 20, the frequency must be ±2 (Hz).
Furthermore, since the sideband components are suppressed through the filter circuit 14 and only the fundamental wave component is transmitted, it is difficult to transmit the relay signal to the receiving station 20 as in the conventional method. , it is possible to transmit using an extremely small frequency band without having to prepare a wide frequency band.

Further, in the relay device 4, the distance measurement signal PDT obtained via the antenna 11 is converted into a predetermined low frequency signal via a frequency conversion circuit 21 and a filter circuit 22, and then
Carrier wave signals SCI to SC4 of the ranging signals PDTI to PDT4 converted into predetermined low frequency signals are obtained via the east circuit 23 and the filter circuit 24.

That is, the squared signal SM2 of the ranging signal PDT1 obtained from the satellite IA is obtained by substituting the formula A(t) in place of the formula A(t-τ) in the formula (9).・(1
0) can be expressed as

Here, the formula A(t) is expressed as a value of 1 or -1 with respect to a change in the C/A code signal, so if the square component of the signal component is extracted with a predetermined filter circuit, A signal component having twice the frequency of the carrier signal expressed by the following equation can be obtained.

Therefore, in FIG. 2, after frequency-converting the distance measurement signal PDT1 into a low-frequency signal, the carrier signal component is extracted via the 2-east circuit 23 and the filter circuit 24. A signal SCI can be obtained.

Similarly, ranging signals PDT obtained from other satellites IB to ID
2 to PDT4 as well, carrier wave signals SC2 to SC4 converted into low frequency signals can be obtained.

In reality, the carrier wave signal of the ranging signal PDT has a shorter wavelength than the C/A code signal, so if the moving distance of the moving object 2 is determined based on the phase difference of the carrier wave signal, the C/A code signal can be
The moving distance of the moving body 2 can be calculated with much higher accuracy than when the moving distance of the moving body 2 is measured using the clock signals CKI to CK4 of the A code signal.

However, when measuring the moving distance of a moving object based on the phase difference between two signals in this way, if the moving object moves a large distance compared to the wavelength during the measurement period, it is difficult to calculate the correct moving distance. There are problems that make it difficult.

Therefore, by transmitting a short-wavelength carrier wave signal and a long-wavelength C/A code signal clock signal from the moving body 2, the moving distance can be calculated using one or both of the carrier wave signal and the clock signal as necessary. Therefore, even when the mobile object 2 moves a long distance, the distance traveled can be calculated with high accuracy using both signals.

The frequency conversion circuit 25 converts the carrier wave signals SCI to SC4 into
is frequency-converted to a predetermined frequency to obtain a relay signal S2, and the relay signal S2 is transmitted to the receiving station 20 via the adding circuit 16 and the antenna 17.

In this case, the carrier wave signals S01 to SC4 are used as the clock signal CK.
Even if it is transmitted at the same time as I to CK4, the distance measurement signal P
The center frequency of DTI to PDT4 as a whole is ±5 (kHz
), the frequency bandwidth required for transmission can be extremely narrow compared to the conventional one.

As shown in FIG. 5, the receiving station 20 receives the relay signals S1 and S2 via the antenna 30, and then receives the clock signal C via the frequency conversion circuit 31 and the filter circuit 32.
KI to CK4 are demodulated and output to the phase difference detection circuit 33.

The phase difference detection circuit 33 detects changes in the phase difference between the clock signals CKI to CKJ and calculates the moving distance and moving direction of the moving body 2 based on the above-mentioned measurement principle.

Furthermore, the phase difference detection circuit 33 calculates the position of the moving body 2 based on the initial installation position information of the moving body 2 obtained in advance when the moving body 2 was installed based on the negative detection signal.

On the other hand, the frequency conversion circuit 34 converts the relay signal S2 into
After frequency conversion, the carrier wave signal 5CI-3 is outputted via the filter circuit 35 to the phase difference detection circuit 33.
Output C4.

The phase difference detection circuit 33 corrects the movement distance and movement direction of the mobile body 2 obtained based on the clock signals CK1 to CK4 based on the change in the phase difference of the carrier wave signals SCI to SC4, and detects the movement distance and movement direction of the mobile body 2. Calculate the position.

In the above configuration, the distance measurement signal PDT of each satellite IA to ID
Clock signals CKI to CK4 of C/A code signals are obtained from I to PDT4 via a delay circuit 13, a multiplication circuit 12, and a filter circuit 14.

On the other hand, carrier wave signals SCI to SC4 obtained by low frequency conversion of the ranging signals PDTI to PDT4 are obtained via the square amplification circuit 23 and the filter circuit 24.

Clock signals CK1 to CK4 and carrier signals 5C1-3
C4 is converted into predetermined relay signals S1 and S2 via frequency conversion circuits 15 and 25, and then transmitted to receiving station 20 via addition circuit 16 and antenna 17.

In the receiving station 20, the relay signals S1 and S2 are demodulated into clock signals CK1 to CK4 and carrier signals sci to SC4 via frequency conversion circuits 31 and 34 and filter circuits 32 and 35, respectively, and then demodulated to a phase difference detection circuit. 3
3 is input.

In the phase difference detection circuit 33, each clock signal CK1~
Changes in phase difference between GK4 and carrier signals 301 to 304
After the moving direction and moving distance of the moving body 2 are calculated based on the change in the phase difference between .

According to the above configuration, the clock signal of the C/A code signal is obtained from the ranging signal, and after transmitting this to the receiving station, the position of the moving object 2 is calculated based on the change in the phase difference of the clock signal. Therefore, the position of the mobile object can be calculated at the receiving station without using a wide frequency band for transmitting the relay signal.

In addition, in the above-mentioned embodiment, a case was described in which the position of the moving object is calculated based on information on the initial setting position of the moving object, but the present invention is not limited to this. Even if there is no IA of each satellite at the receiving station.
If the orbit information of the ~ID is obtained, the position of the moving object can be calculated based on the orbit information of the satellite IA~ID by measuring the change in the phase difference of each clock signal over a predetermined period of time. can.

Further, in the above embodiment, a case was described in which the clock signal and carrier wave signal of the C/A code signal are transmitted to the receiving station, but the present invention is not limited to this. You may also send

Furthermore, instead of the clock signal of the C/A code signal, a clock signal of the P code signal may be transmitted. In this case, the delay time of the delay circuit 13 may be selected to be 1/10 of the time for the C/A code signal.

Further, in the above-described embodiment, a case was described in which the clock signal of the C/A code signal is obtained from a ranging signal with a center frequency of 1575.42 (MHz), but in the present invention, instead of this, a clock signal with a center frequency of 1227.6 (MHz) is obtained. ) may be obtained from the ranging signal.

Furthermore, in the above-described embodiment, a case has been described in which the clock signal is frequency-converted and transmitted to the receiving station, but the present invention is not limited to this. It is also possible to send it by

In this case, even if frequency modulation is performed, the frequency band will be approximately 100 (
The clock signal can be transmitted with sufficient accuracy for practical use in a band of about kHz), and the frequency bandwidth for transmission may be narrower than that of the conventional technology.

Furthermore, in the above-described embodiments, the present invention has been described with respect to the case where the position of one moving object is detected, but the present invention is not limited to this and can be applied to cases where there are a plurality of moving objects.

Furthermore, in the above-mentioned embodiment, the case where the present invention is applied to the position measurement of a moving body has been described, but the present invention is not limited to this. It can be widely applied to measurements, etc.

Further, in the above-described embodiment, the case where the present invention is applied to a GPS system has been described, but the present invention is not limited to this, and the present invention is not limited to this. It can be widely applied to position measurement systems that calculate information.

Effects of the Invention As described above, according to the present invention, by transmitting the clock signal of the code signal of the spread spectrum signal received by the repeater to the receiving station, it is possible to operate the middle W and equipment without using a wide frequency band. The position of the mounted moving object can be calculated.

Fig. 2 is a block diagram showing the configuration of the relay equipment, Fig. 3 is a signal waveform diagram explaining the clock signal of the C/A code signal, and Fig. 4 is an explanation of the principle of position measurement. The route map provided in FIG. 5 is a block diagram showing the configuration of the receiving station.

IA, IB, IC, ID...Satellite, 2...
・・Mobile object, 12・・・・Multiplication circuit, Engineering 3・・・・
...Delay circuit, 14.22.241.32.35...
...Filter circuit, 15.21.25.31.34.
... Frequency conversion circuit, 20 ... Receiving station,
33... Phase difference detection circuit.

Claims (1)

[Scope of Claims] A position measurement system configured to calculate the receiving position of the distance measurement signal based on the distance measurement signal spread spectrum with a predetermined code signal and transmitted from a plurality of signal generation sources. a relay device that receives the ranging signal, obtains a clock signal of the code signal, and transmits the clock signal; and a relay device that receives the clock signal transmitted from the relay device and calculates the phase difference between the clock signals. and a receiving station that calculates the receiving position of the relay device based on the information.