JP3344377B2 - Pseudo GPS satellite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a quasi-GPS satellite, and more particularly to a quasi-GPS satellite which radiates a transmission radio wave equivalent to a GPS satellite and has an output control function.

[0002]

2. Description of the Related Art As is well known, GPS (Glob
al Positioning System: 4
This is a positioning system that calculates the position of a moving object by measuring the apparent distance from at least two artificial satellites (GPS satellites) to the moving object. At this time, the positioning accuracy is affected by the arrangement of the GPS satellites. The most accurate measurement arrangement is when the GPS satellite is located at the apex of a tetrahedron and the mobile is located at its center. The arrangement in which the accuracy degrades most is when the GPS satellites are concentrated at one point. An index called DOP (Dillution of Precision) is used as an index indicating the degree of deterioration of position accuracy due to the arrangement of satellites.

[0003] Landing systems using such GPS are being constructed worldwide. However, since the GPS satellites are all above the vehicle, there is a need to improve the altitude DOP required for landing the aircraft. For this reason, a method of improving the accuracy in the altitude direction by installing a pseudo GPS satellite on the ground is being studied. Here, the pseudo GPS satellite is
It refers to a ground device that emits transmission radio waves equivalent to GPS satellites.

However, when the accuracy in the altitude direction is improved by the pseudo GPS satellite, the following distance problem of the pseudo GPS satellite occurs. GPS satellites have an orbit altitude of 20,000
It travels around 0 km, and the average reception level on the ground is about -130 dBm. This value is inversely proportional to the square of the distance between the GPS satellite and the moving object. However, since the GPS satellite is far enough, the level fluctuation is only about 3 dB.

On the other hand, since the pseudo GPS satellite is installed on the ground, the distance between the pseudo GPS satellite and the moving object greatly changes, and the received power also greatly changes. For example, assuming the mobile is an aircraft, the aircraft enters a final approach from 25 NM,
Consider the case of landing at the runway edge (0.5 NM). In this case, the fluctuation of the received power is accompanied by a large change of 33.9 dB due to the approach from 25 NM to 0.5 NM. Therefore, a normal GPS receiver having only a dynamic range of about 10 dB, which is mounted on a moving body, has saturation of a receiving unit, and cannot receive signals normally. This is the near-far problem of the pseudo GPS satellite.

[0006] This relationship will be described in detail. Figure 9 shows GPS
FIG. 2 is a diagram illustrating a positional relationship between a satellite group and a moving object on the earth. In the figure, the GPS satellite group 21 is located at an altitude of 20,0001 km above the earth 45. Mobile object is Earth 45
When at the point A above, the distance P0 closest to the GPS satellite group 21 is P0 = 14,000 km since the radius r1 of the earth 45 is 6,000 km. On the other hand, when the moving object is located at the point B on the earth 45, the distance P1 from the GPS satellites 21 is obtained by the following equation.

[0007]

(Equation 1)

Here, in the equation (1), θ is an angle formed between the point A, the center point of the earth 45 and the point B as shown in FIG.
If θ is, for example, 60 degrees, the distance P1 is 1 from the equation (1).
7,776 km, and the increase in propagation loss is at most 0.91
dB.

Next, the principle of the occurrence of the saturation phenomenon in the receiver of the GPS receiver will be described with reference to FIGS.
FIG. 10 shows a correlation process in a normal case. When a signal having an amplitude of 1 is received from each of the satellites Nos. 1 to 4, the received signal looks like noise at first glance, as indicated by the solid line in FIG. This received signal is sampled by 1 bit, and the product of the received signal and the gold code of the satellite with the satellite number 1 shown in FIG. 10B (which is a known pseudo-random sequence as described later) is obtained. As shown in FIG. 10C, the integration result of the value of the product is “12”. This state indicates that the correlation has been obtained.

On the other hand, FIG. 11 shows a case where the signal of the satellite having the satellite number 4 is increased by 10 times (20 dB). Because of the strong signal, the received signal is partially saturated as shown by the solid line in FIG. In the example of FIG. 11A, the saturation level is set to “10”. In this state, the received signal subjected to the same correlation processing as in FIG.
When the product of the satellite number 1 and the gold code shown in (B) is taken, the multiplication result is as shown in FIG.
The integration result of the value of this product is "4". If the threshold is set to "8" with a margin from the half value of "12", which is the peak, it is not determined that the reception was correct when the correlation output was "4". That is, it is understood that reception is not possible.

[0011] As described above, the approach of the pseudo GPS satellite greatly changes the distance when the pseudo GPS satellite is approached, saturates the receiver of the GPS receiver, and makes it impossible to perform positioning in the mobile body. Called the perspective problem.

[0012]

SUMMARY OF THE INVENTION A pseudo GPS
The satellite must synchronize with the external GPS.
Therefore, it is necessary to receive a GPS signal from a GPS satellite group. The most ideal time is the GPS time measured at the pseudo GPS transmission antenna. However, pseudo GP
The output of the S satellite is high, and when transmitting with a continuous wave, saturation of the receiving unit occurs, and the above-mentioned distance problem of the pseudo GPS satellite occurs. For this reason, it is necessary to isolate the GPS receiving antenna from the pseudo GPS transmitting antenna in terms of radio waves.

[0013] The simplest method of this isolation is to spatially separate the two antennas. However, if the antenna is far away, an error occurs between the time at which the pseudo GPS satellite should be synchronized and the measured GPS time. The time difference is equal to the time required for the radio wave to propagate between the antenna and the feeder. Therefore, there is a demand for a method of taking isolation between the two in a close state.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a pseudo GPS satellite that can improve the position determination accuracy by controlling the output of the pseudo GPS satellite without causing a GPS signal saturation phenomenon.

It is another object of the present invention to provide a pseudo-GPS satellite in which a near-far problem hardly occurs even when a continuous wave is transmitted.

[0016]

In order to achieve the above object, the present invention provides a GPS antenna for receiving a GPS signal transmitted from a GPS satellite constellation, a GPS signal received by a GPS antenna, and a GPS antenna. A GPS receiver for detecting a GPS time from absolute coordinates, a pseudo GPS signal generating means for generating a pseudo GPS signal composed of a pseudo random code for distance measurement and pseudo GPS data, and a pseudo GPS signal detected by the GPS receiver Synchronous state monitoring means for detecting a difference between the base clock of the pseudo GPS signal input from the GPS signal generation means and the detected clock difference information on the pseudo GPS signal output from the pseudo GPS signal generation means; A configuration including a GPS antenna, an optimal level calculating unit, a level varying unit, an azimuth calculating unit, and an antenna rotating unit is provided. It is.

Here, the pseudo GPS aerial is a moving object position detecting means for detecting the position of the moving object and an aerial having a null, and the pseudo GPS aerial is a pseudo aerial having the null direction set to the GPS aerial. This is an antenna for transmitting GPS signals. In addition, the above-mentioned optimum level calculation means uses the pseudo GP
The optimum transmission output of the pseudo GPS antenna is calculated based on the coordinates of the S antenna and the position coordinates of the moving object detected by the moving object position detecting means. Further, the above-mentioned level varying means outputs the pseudo GP signal output from the pseudo GPS signal generating means in accordance with the transmission output calculated by the optimum level calculating means.
The level of the signal consisting of the S signal and the clock difference information is varied and supplied to the pseudo GPS antenna. Further, the azimuth calculating means calculates azimuth information of the pseudo GPS antenna with respect to the moving object in a polar coordinate system centered on the pseudo GPS antenna based on the position coordinates with the moving object detected by the moving object position detecting means. . Further, the above-described antenna rotating means performs the pseudo G based on the azimuth information calculated by the azimuth calculating means.
While pointing the maximum gain direction of the PS antenna to the moving object,
The null direction of the pseudo GPS antenna is always directed to the GPS antenna.

According to the present invention, the optimum transmission output of the pseudo GPS antenna is calculated based on the coordinates of the pseudo GPS antenna and the position coordinates of the moving object, and the signal including the pseudo GPS signal and the clock difference information is calculated from the calculated transmission output. Since the level of a signal transmitted to be transmitted from the pseudo GPS antenna to the mobile unit is made variable, the received signal strength of the transmission signal transmitted from the pseudo GPS antenna at the mobile unit can always be made substantially constant. it can.

According to the present invention, in order to achieve the above object, the antenna rotating means includes an omnidirectional GPS antenna disposed immediately above the turntable rotation axis, and disposed around the turntable rotation axis. And a turntable structure in which a pseudo GPS antenna whose null direction is set to the GPS antenna direction is arranged. In the present invention, the direction of the null of the pseudo GPS antenna is set to the direction of the GPS antenna, and the maximum gain direction of the pseudo GPS antenna is in the opposite direction to the null direction.
Regardless of which direction the S antenna is oriented, the isolation from the GPS antenna can be maximized.

According to the present invention, in order to achieve the above object, the pseudo GPS signal generating means includes: a clock for generating a clock; a generator for generating a pseudo random sequence based on the clock; A pseudo satellite data generator for generating a navigation message indicating clock difference information, an adder for superimposing a pseudo random sequence on a publication message,
An oscillator that generates a continuous wave carrier in synchronization with a clock from a clock; and a modulator that modulates the carrier with an output signal of an adder and outputs a modulated wave signal as a signal including a pseudo GPS signal and clock difference information. The synchronization state monitoring means detects the difference between the GPS time detected by the GPS receiver and the clock input from the clock, and outputs the detected clock difference information to the pseudo satellite data generator as the clock difference information of the navigation message. It is characterized by comprising a time difference detector for input.

According to the present invention, the carrier of the signal transmitted by the pseudo GPS antenna can be a continuous wave, so that the navigation message can be superimposed.

Further, according to the present invention, the moving body position detecting means comprises:
A radar device that emits a radio wave from a rotating directional antenna and reflects it from the moving object, and detects the position of the moving object from the direction of the reflected radio wave from the moving object and the round trip time of the radio wave, and a predetermined service should be provided The target detector extracts only the position information of the moving object to be serviced by correlating the route and schedule of the moving object with the current position information of the moving object from the radar device.

Further, according to the present invention, the optimum level calculating means includes:
From the inclination distance calculated from the pseudo GPS antenna and the moving object detected by the moving object position detecting means, the carrier frequency of the signal radiated from the pseudo GPS antenna, the gain of the pseudo GPS antenna, and the gain of the GPS antenna of the moving object. It is characterized by comprising a path loss calculator which calculates a path loss and controls a variable level of the level varying means so that the calculated path loss becomes a predetermined value.

[0024]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a pseudo GPS according to the present invention.
FIG. 2 shows a block diagram of one embodiment of a satellite. In FIG. 1, a pseudo GPS satellite signal generating means 101 generates a pseudo random code for measuring the distance of a GPS signal and pseudo GPS data. Pseudo GPS satellite group 2 in pseudo GPS data
1 contains data representing the difference between the antenna position, the pseudo GPS satellite clock and the GPS time, the ID number of the pseudo satellite, and the coordinates of the pseudo satellite. The output signal of the pseudo GPS satellite signal generating means 101 is supplied to the antenna rotating means 107 after the level is changed to an optimum value by the level changing means 105.

On the other hand, the position of the moving body 20 is detected by the moving body position detecting means 103. There are various methods for this position detection. In general, the antenna 102 is used because the information from the mobile unit 20 is easily performed by a system using radio waves. The data of the position coordinates of the moving body 20 detected by the moving body position detecting means 103 are input to the optimum level calculating means 104 and the azimuth calculating means 106, respectively.

The optimum level calculation means 104 is a pseudo GPS
The distance between the antenna 108 and the position of the moving object 20 is calculated using the position coordinates, and the radio wave propagation loss is calculated from the calculated distance information. Further, the optimum level calculation means 104 calculates an optimum transmission output of the pseudo GPS satellite from the calculated radio wave propagation loss, the pseudo GPS antenna gain, and the cable loss. This calculation result is input to the level varying means 105.

The azimuth calculating means 106 converts the position of the moving body 20 into a polar coordinate system centered on the position coordinates of the pseudo GPS antenna 108, and inputs azimuth information from the obtained conversion result to the antenna rotating means 107. . Antenna rotation means 107
A normal GPS antenna 109 is mounted just above the axis, and a pseudo GPS antenna 108 is mounted around the axis away from the axis. The antenna rotating means 107 has a turntable structure, and determines the maximum gain direction of the pseudo GPS antenna 108 according to the azimuth information input from the azimuth calculating means 106.
Point to zero.

The pseudo GPS antenna 108 is an antenna having a null, and the null direction is the GPS antenna 109 on the axis.
Is set to The maximum gain direction is in the direction directly opposite to null. Therefore, the null direction of the pseudo GPS antenna 108 is GP regardless of the direction of the antenna rotating means 107.
It is characterized in that it faces the S antenna 109 direction.

A signal from the GPS satellite group 21 is received by the GPS antenna 109. The GPS antenna 109 can stably receive signals radiated from the GPS satellites 21 without being affected by the rotation of the antenna rotating means 107 and the magnitude of the pseudo GPS transmission output. This is because the null direction of the pseudo GPS antenna 108 is directed to the GPS antenna 109 and the maximum isolation is obtained.

The output signal of the GPS antenna 109 is supplied to a GPS receiver 110. The GPS receiver 110 precisely detects the GPS time from the input received GPS signal and the absolute coordinates of the GPS antenna 109. Synchronization state monitoring means 11
1 is the above GPS input from the GPS receiver 110
The difference between the time and the basic clock of the pseudo GPS input from the pseudo GPS signal generating means 101 is detected.

The clock difference between the external GPS satellite group 21 and the pseudo GPS satellite causes an error in the position calculation result in the mobile unit 20. Therefore, the difference between the GPS time obtained by the synchronization status monitoring means 111 and the pseudo GPS clock is added to the satellite information superimposed on the pseudo GPS satellite.
The pseudo GPS signal is incorporated in the signal generating means 101 and the pseudo GPS signal is passed through the level varying means 105.
8 to the mobile unit 20.

A conventional method for maximizing isolation between transmitting and receiving antennas is disclosed in Japanese Patent Application Laid-Open No. 10-2003.
An antenna device described in Japanese Patent Publication No. 26 is known. This antenna device is arranged as a transmitting and receiving antenna formed on a plane, polyhedron or curved ground conductor, and so as to substantially maximize the isolation between the transmitting and receiving antennas. It has a structure that rotates by a specific angle with respect to the vertical axis, and has a transmission and reception microstrip antenna for circularly polarized wave excitation. However, in this device, the isolation is maximized by using a partition plate or reflection scattering between the transmitting antenna and the receiving antenna that do not have directivity. Not used, and the pseudo GPS antenna 108 as a transmitting antenna is for directing radio waves to the mobile unit 20 with directivity, and the GPS antenna 109 as a receiving antenna is omni. This is a completely different configuration.

Next, the operation of this embodiment will be described. The GPS signal transmitted from the GPS satellites 21 is received by the GPS antenna (not shown) of the mobile unit 20, while the GPS antenna 109 of the present embodiment also receives the pseudo GP signal.
It is received stably without being affected by the magnitude of the S transmission output.
The GPS signal from the GPS satellites 21 received by the GPS antenna 109 is supplied to a GPS receiver 110, where the GPS time is precisely detected from the received GPS signal and the absolute coordinates of the GPS antenna 109.

The synchronization status monitoring means 111 compares the GPS time input from the GPS receiver 110 with the pseudo GPS
The pseudo GPS signal generating means 101 detects the difference between the basic clocks of the pseudo GPS input from the signal generating means 101 and uses the pseudo GPS signal generating means 101 as clock difference information (clock correction value) for correcting an error in the position calculation result in the moving body 20. Supplied to The pseudo-GPS signal generating means 101 generates a pseudo-random code (gold code described later), and also outputs the positions of the antennas 108 and 109, the clocks of the pseudo-GPS satellites, and data such as satellite identification numbers from the synchronization state monitoring means. The difference information is added and output to the level varying means 105. Further, the clock of the pseudo GPS satellite is also supplied to the synchronization state monitoring means 111.

On the other hand, the position coordinates of the moving body 20 are detected by the moving body position detecting means 103 using the radio wave from the antenna 102 and the moving body 20, and the position coordinate data is converted into the optimum level calculating means 104 and the azimuth calculating means 106. Supplied to each. As described above, the optimum level calculation means 104 sequentially calculates distance information and radio wave propagation loss using the pseudo GPS antenna 108 and the position coordinates of the moving object 20, and further calculates the radio wave propagation loss and the pseudo GPS antenna gain. Then, the optimum transmission output of the pseudo GPS satellite is calculated from the cable loss and input to the level varying means 105. As a result, a pseudo GPS signal (including clock difference information) controlled so that the transmission level is optimized, that is, the signal strength received by the mobile unit 20 is constant, is extracted from the level varying unit 105. It is supplied to the pseudo GPS antenna 108 and transmitted therefrom.

The azimuth calculating means 106 determines whether the moving object 20
Is converted to a polar coordinate system centered on the position coordinates of the pseudo GPS antenna 108, and of the obtained conversion results, the azimuth information is input to the antenna rotating means 107, and the maximum gain direction of the pseudo GPS antenna 108 is 20 directions
The rotation of the antenna rotating means 107 is controlled. As a result, the signal strength of the pseudo GPS signal received by the mobile unit 20 becomes constant, and the GPS signal saturation phenomenon in the mobile unit 20 equipped with the GPS receiver can be greatly reduced. For this reason,
It is possible to solve deterioration of GPS positioning accuracy due to a change in signal strength, that is, a so-called bias problem.

In the present embodiment, since the signal strength is constant, the mobile unit 20 can perform positioning after receiving each transmission signal from the pseudo GPS satellite and the GPS satellite group 21 until reaching the vicinity of the pseudo GPS satellite. Improved positioning accuracy by improving GPS, and the effectiveness of GPS positioning service (Av
ailability) can be improved. In addition, pseudo GPS antenna 1
08 and the GPS antenna 109 while keeping them isolated, the time synchronization of the pseudo GPS satellite can be made to exactly match the GPS time of the world, and thus the emission radio wave of the pseudo GPS satellite can be obtained. Accuracy can be increased.

[0038]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing one embodiment of the pseudo GPS satellite according to the present invention. In the figure, the same components as those in FIG. 1 are denoted by the same reference numerals. In FIG. 2, a cesium clock 1, a gold code generator 2, a pseudo satellite data generator 3, an exclusive OR circuit (hereinafter abbreviated as XOR) 4,
The BPSK modulator 5 and the phase locked oscillator 6 are pseudo GPS
The signal generating means 101 is included.

The radar device 7 and the target detector 8 connected to the antenna 102 constitute a moving body position detecting means 103. Further, the propagation loss calculator 9 includes the optimum level calculating unit 104, and the variable attenuator 10 includes the level varying unit 10.
5, the polar coordinate conversion calculator 11 sets the azimuth calculating means 106,
The antenna rotating table 12 constitutes the antenna rotating means 107, and the time difference detector 13 constitutes the synchronization state monitoring means 111.

First, the pseudo GPS signal generating means 101 will be described. Figures 3-6 show the Department of Defense (Department of
Defense) ("GLOBAL POSITIONING
SYSTEM STANDARD POSITIONING SERVICE SIGNAL SPECIFI
CATION "(2nd Edition June 2, 1995). FIG. 3 shows a method of generating a C / A code open to the private sector, and shows the gold code generator 2 of FIG. In the figure, a G1 generator 31 and a G2 generator 32 are a shift register 3 having feedback.
3 and 34, two predetermined bit output signals S1 and S2 of the shift register 34 are selected by a phase selector 35, and the selected signal is added to an output signal of the G1 generator 31 by an adder 36. , A pseudo random sequence (C / A code) called a GOLD CODE.

The clock generator 37 has 1.023M.
A BPS clock is generated, and the initial setting circuit 38 sets all "1" in the shift registers 33 and 34 at the start. The decoder 38 decodes the output of 1.023 MBPS and outputs a signal of 1 KBPS.
Divides by 20 to generate a 50 BPS data clock and outputs it to the pseudo satellite data generator 3 in FIG.

FIG. 4 is a configuration diagram of an example of the G1 generator 31, and FIG. 5 is a configuration diagram of an example of the G2 generator 32. In both figures, the same components as those in FIG. 3 are denoted by the same reference numerals. The setting method of the satellite number and the phase selector 35 is determined, and is shown in FIG. Currently there are less than 30 GPS satellites (28 as of February 1999), and 33-3
By broadcasting the signal of the seventh satellite, it is possible to recognize that it is a pseudolite existing on the ground.

According to FIG. 6, in the case of the 33rd satellite, tap number 5 and tap number 10 are XORed in the G2 generator 32 shown in FIG. 5, and if G2I is generated, the pseudo GPS signal is used for distance measurement. Can be generated. 1.023MBPS CL in FIG.
1.023M divided from cesium clock 1 in OCK part
Hz clock signal.

On the other hand, identification of pseudo GPS satellites and coordinates,
The data indicating the clock correction value is “50B” shown in FIG.
Using “PS DATA CLOCK” as a clock, FIG.
Is generated by the pseudo satellite data generator 3. This data is generally called a navigation message because it is necessary for the mobile unit to perform the navigation calculation. A method of superimposing a navigation message on a pseudo-random sequence (gold code) is widely known (newly revised edition "GPS-precise positioning system by artificial satellite-", edited by the Geodetic Society of Japan, p. 72).

The bit string created by superimposing the navigation message on the pseudo random sequence (gold code) by the adder 4 is a BPSK (Binary Phase Shift Key).
ing) The data is supplied to the modulator 5 and BPSK modulated. The BPSK modulator 5 modulates the continuous wave carrier signal (1575.42 MHz) input from the phase locked oscillator 6 into two phase states of 0 degree and 180 degrees according to the bit string from the adder 4. This method is well known and may use a ring modulator using a mixer or a phase shifter type in which a signal path having a phase difference of 180 degrees is switched by a PIN diode or the like. The phase-locked oscillator 6 is based on a stable clock input from the cesium clock 1
1575.4 which is the carrier frequency of the GPS L1 signal
Generates 2 MHz.

On the other hand, the radar device 7 and the antenna 102 shown in FIG. 2 are used to accurately grasp the position of the mobile unit 20. The radar device 7 is well known,
Radio waves are emitted from the directional antenna 102 rotating with respect to 0, and the distance is calculated from the direction and the time the radio waves reciprocate.

The radar device 7 can obtain position information of a plurality of moving objects. From these, it is necessary to detect the target to be serviced by the pseudo GPS satellite. The target detector 8 correlates a predetermined route and schedule with the current position of the mobile unit, and determines the mobile unit 20 to be serviced. If a secondary radar is used, the mobile unit 20
, And this processing can be enhanced. The position of the moving object to be serviced is decomposed into X and Y coordinates corresponding to the earth's surface and Z coordinates corresponding to the vertical direction and output.

In the propagation loss calculator 9, the coordinates of the mobile unit 20 to be serviced outputted from the target detector 8 and the pseudo GPS
The propagation loss is calculated from the relative relationship between the coordinates of the antenna 108. Now, assuming that the coordinates of the moving object 20 are (x, y, z) and the coordinates of the pseudo GPS antenna 108 are (x0, y0, z0), the inclination distance ρ between the pseudo GPS antenna 108 and the moving object 20 is as follows. It can be obtained by the formula.

[0049]

(Equation 2) Further, the propagation loss L0 can be obtained by the following equation.

(Equation 3)

Here, in equation (3), λ is the wavelength of the GPS L1 signal (1575.42 MHz), and G1 is the pseudo GPS
G2, the gain of the antenna 108, is the gain of the GPS antenna of the mobile unit 20. These can be known in advance when designing the system.

Now, the service for the mobile unit 20 is 25
0.5 NM from NM (NM is nautical miles). The propagation loss at 25 NM is L1, and the propagation loss at a certain time is L2.
Then, when the moving body 20 approaches, it is L1L2.
Assuming that the current setting value of the variable attenuator 10 is α, α is obtained by the following equation.

Α = L1 / L2 (4) When the variable attenuator 10 indicates the set value α,
The strength of the pseudo GPS signal received by the mobile unit 20 at a certain time is the same as the strength at the time of 25 NM.

The signals output from the target detector 8 and indicating the coordinates of the moving object 20 to be serviced and the coordinates of the pseudo GPS antenna 108 are also supplied to the polar coordinate conversion computer 11. The polar coordinate conversion computer 11 uses the x and y coordinates to calculate x
The angle θ from the axis is obtained by the following equation.

[0054]

(Equation 4)

The polar coordinate conversion computer 11 sends a drive signal to the antenna turntable 12 based on the angle θ obtained by the equation (5) so that the maximum gain direction of the pseudo GPS antenna 108 is directed to the direction of the mobile unit 20. Supply.

The antenna turntable 12 has, for example, a turntable structure shown in FIG. As shown in the figure, the antenna turntable 12 has a rotary joint 4 inside a center of a disk-shaped base (turntable) 42 having a center as a rotation axis.
3 is provided to connect the antenna to the outside at high frequency regardless of rotation. The GPS antenna 109 is omnidirectional, and can capture signals from the GPS satellites 21 regardless of the rotation of the antenna turntable 12. The pseudo GPS antenna 108 has directivity characteristics. In this example, an antenna is shown in which the power supply of the element e2 is delayed by 90 ° with respect to the element e1 and the spatial interval is arranged at an electrical length of 120 °. Further, e3 indicates a reflector. FIG. 8 shows the directivity characteristics of the pseudo GPS antenna 108.

As shown in the figure, a null is formed in the direction opposite to the maximum gain direction, and there is an attenuation of about 20 dB with respect to the maximum gain. The half width of the pattern is 135 °, and the moving body 2
If the direction of 0 is captured within ± 10 °, the change in G1 due to the pattern can be ignored.

Returning to FIG. 2, the GPS receiver 110 receives the output signal of the GPS antenna 109 provided on the antenna turntable 12 and detects the GPS time by the positioning calculation. This is a 1-Hz pulse called 1PPS, which is input to the time difference detector 13. The time difference detector 13 detects the GPS time and the pseudo GPS signal
The difference from the main clock from the cesium clock 1 is measured. This difference is output to the pseudo satellite data generator 3 as the satellite time difference of the navigation message. By this series of processing, the GPS time and the delay system of the pseudo GPS satellite are synchronized,
The navigation calculation in the moving body 20 can proceed smoothly.

According to this embodiment, by controlling the amount of attenuation of the variable attenuator 10 by the value of the equation (4), the moving body 20 is controlled.
Is always at the level of 25 NM. Therefore, in this embodiment, since the signal strength of the receiving unit of the GPS receiver in the mobile unit 20 is constant, the saturation phenomenon does not occur, so-called distance problem can be solved, and the GPS positioning accuracy due to the change of the signal strength can be solved. Degradation, a so-called bias problem, can be solved.

Further, positioning using both the GPS and the pseudo GPS is possible in the mobile unit 20 up to the vicinity of the pseudo GPS satellite, the accuracy of position determination is improved by improving the DOP, and the effectiveness of the GPS positioning service is improved. Can be improved. Further, since the signal of the pseudo GPS satellite can be a continuous wave, the positioning time can be made longer than that of the pseudo GPS satellite using pulses, the accuracy by averaging is improved, and the navigation message can be superimposed. It is possible to carry GPS augmentation data in this navigation message. Thereby, a highly reliable system can be constructed.

Further, since the GPS antenna 109 and the pseudo GPS antenna 108 can be installed close to each other while isolating them, the time synchronization of the pseudo GPS satellite can be made to exactly coincide with the global GPS time.

The present invention is not limited to the above embodiments and examples. For example, the moving object position detecting means 103 may be provided not only with the radar device 7 but also with a system capable of notifying the position by communication. Obviously, the configuration can be replaced.

In the case of an aircraft, a typical example of other monitoring systems is ADS-C or -B (Automatic Dependent Surv.
As in the case of eillance -Contract or -Broadcast, a method of measuring the arrival time of SSR signals normally transmitted by an aircraft at three antennas on the ground and calculating the position of the aircraft from the difference is conceivable.

In the case where the moving object is an automobile, a method of transmitting the position of the car by using a mobile phone, spread spectrum radio, or the like is conceivable.

[0065]

As described above, according to the present invention,
Since the received signal strength at the mobile body of the transmission signal transmitted from the pseudo GPS antenna can always be almost constant,
The saturation phenomenon does not occur, so that the so-called distance problem can be solved, and the deterioration of the GPS positioning accuracy due to the change in the signal strength, that is, the so-called bias problem can be solved.

Further, according to the present invention, since the distance problem can be solved, it is possible to perform positioning of a moving object using both the GPS and the pseudo GPS up to the vicinity of the pseudo GPS satellite.
The position determination accuracy of the moving object can be improved by improving the DOP,
Further, the effectiveness of the GPS positioning service can be improved.

Further, according to the present invention, since the signal of the pseudo GPS satellite can be converted into a continuous wave, the pseudo GPS
The positioning time can be longer than that of a satellite, and the accuracy by averaging can be improved.

According to the present invention, since a continuous wave is used, a navigation message can be superimposed, and GPS augmentation data can be carried in the navigation message. Thereby, a highly reliable positioning system can be constructed.

Further, according to the present invention, since the GPS receiving antenna and the pseudo GPS transmitting antenna can be installed close to each other while isolating them, the time synchronization of the pseudo GPS satellite can be accurately synchronized with the global GPS time. Can be matched. For this reason, the accuracy of the radio wave emitted from the pseudo GPS satellite can be improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram of one embodiment of the present invention.

FIG. 3 is a circuit diagram of an example of a gold code generator in FIG. 2;

FIG. 4 is a configuration diagram of an example of a G1 generator in FIG. 3;

FIG. 5 is a configuration diagram of an example of a G2 generator in FIG. 3;

FIG. 6 is a diagram showing a setting method of a satellite number and a phase selector.

FIG. 7 is a configuration diagram of an example of the antenna turntable in FIG. 2;

FIG. 8 is a diagram illustrating directivity characteristics of a pseudo GPS antenna.

FIG. 9 is a diagram showing a positional relationship between a GPS satellite group and a moving object on the earth.

FIG. 10 is an explanatory diagram of a correlation process when the receiving unit of the GPS receiver is in a normal state.

FIG. 11 is an explanatory diagram of a correlation process when the receiving unit of the GPS receiver is in a saturated state.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Cesium clock 2 Gold code generator 3 Pseudo satellite data generator 4 Exclusive OR (XOR) circuit 5 BPSK modulator 6 Phase synchronous oscillator 7 Radar device 8 Target detector 9 Propagation loss calculator 10 Variable attenuator 11 Polar coordinate conversion Computer 12 Antenna turntable 13 Time difference detector 20 Moving object 21 GPS satellite group 101 Pseudo GPS signal generating means 102 Antenna 103 Moving object position detecting means 104 Optimal level calculating means 105 Level variable means 106 Azimuth calculating means 107 Antenna rotating means 108 Simulator GPS antenna 109 GPS antenna 110 GPS receiver 111 Synchronization state monitoring means

Continuation of front page (56) References JP-A-11-298225 (JP, A) JP-A-11-72548 (JP, A) JP-A-6-222128 (JP, A) JP-A-7-113860 (JP, A) JP-A-7-159508 (JP, A) JP-A-8-62323 (JP, A) JP-A-9-9916 (JP, A) Bradford et al., Optimal Locations of Pseudolites for Differential GPS, NAVIGATA. ION: Journal of The Institute of Navigation, United States, The Institute of Navigation, Vol. 33, No. 4, pp. 259-283, Winter 1986-87 Kurt R.C. Zimmerman et al., Experimental Demonstration of an Indoor GPS-Based Sensing System for Robotic Application ins, NAVIGATION in the United States of America. 43, No. 4, pp. 375-395, Winter 1996-1997 (58) Fields investigated (Int. Cl. ⁷ , DB name) G01S 5/00-5/14 G01C 21/00-21/24 G01C 23/00-25/00 H01Q 3/00-3/46 H01Q 21/00-25/04

Claims (6)

(57) [Claims] [Features of the invention] 1. A GPS antenna for receiving a GPS signal transmitted from a GPS satellite constellation; the GPS signal received by the GPS antenna;
GPS that detects GPS time from the absolute coordinates of PS antenna
A receiver; a pseudo GPS signal generating means for generating a pseudo GPS signal comprising a pseudo random code for distance measurement and pseudo GPS data; input from the pseudo GPS signal generating means and the GPS time detected by the GPS receiver A synchronous state monitoring means for detecting a difference between the pseudo GPS signal and a basic clock to be detected and superposing the detected clock difference information on the pseudo GPS signal output from the pseudo GPS signal generating means; A pseudo-GPS antenna for transmitting a pseudo-GPS signal to the moving object, wherein the pseudo-GPS antenna is an antenna having a null, and the direction of the null is set to the GPS antenna. Based on the coordinates of the antenna and the position coordinates of the moving object detected by the moving object position detecting means, the optimum GPS antenna An optimum level calculating means for calculating a signal output, and a level of a signal consisting of the pseudo GPS signal and clock difference information output from the pseudo GPS signal generating means in accordance with the transmission output calculated by the optimum level calculating means. Level varying means for variably supplying the pseudo GPS antenna to the pseudo GPS antenna, and the pseudo GPS in a polar coordinate system centered on the pseudo GPS antenna based on the position coordinates of the moving object detected by the moving object position detecting means. Azimuth calculating means for calculating azimuth information for the moving body of the antenna, based on the azimuth information calculated by the azimuth calculating means,
An antenna rotating means having a structure in which a maximum gain direction of the pseudo GPS antenna is directed to the moving object, and a null direction of the pseudo GPS antenna always faces the GPS antenna direction. satellite. 2. The antenna rotating means, wherein the omnidirectional GPS antenna is disposed immediately above a turntable rotation axis, and around the distance from the turntable rotation axis, and
The pseudo G whose null direction is set to the GPS antenna direction.
The pseudo GPS satellite according to claim 1, wherein the pseudo GPS satellite has a turntable structure in which a PS antenna is arranged. 3. The pseudo GPS signal generating means generates a clock for generating a clock, a generator for generating a pseudo random sequence based on the clock, and a navigation message indicating satellite identification, coordinates and clock difference information. A pseudo-satellite data generator, an adder that superimposes the pseudo-random sequence on the publication message, an oscillator that generates a carrier of a continuous wave in synchronization with the clock from the clock, A modulator for modulating with an output signal and outputting a modulated wave signal as a signal comprising the pseudo GPS signal and the clock difference information, wherein the synchronization state monitoring means includes the GPS time detected by the GPS receiver and the GPS time. A difference from a clock input from a clock is detected, and the detected clock difference information is transmitted to the pseudo-satellite data generator by a clock of the navigation message. 2. The pseudo GP according to claim 1, further comprising a time difference detector for inputting the information as a clock difference information.
S satellite. 4. The moving body position detecting means emits a radio wave from a rotating directional antenna and reflects the radio wave on the moving body,
A radar device for detecting the position of the moving object from the direction of the reflected radio wave from the moving object and the round-trip time of the radio wave; a predetermined route and schedule of the moving object to be serviced; 2. The pseudo-GPS satellite according to claim 1, further comprising a target detector that extracts only the position information of the moving object to be serviced by correlating with the position information of the moving object. 5. The method according to claim 1, wherein the optimum level calculating means is configured to calculate the pseudo G
An inclination distance calculated from a PS antenna and the moving object detected by the moving object position detecting means;
The carrier frequency of the signal radiated from the antenna and the pseudo G
A path loss calculator configured to calculate a path loss from a gain of a PS antenna and a gain of a GPS antenna of the moving object, and to control a level variable amount of the level variable means so that the calculated path loss becomes a predetermined value. The pseudo GPS satellite according to claim 1, wherein 6. The pseudo GPS satellite according to claim 1, wherein the mobile unit position detecting means detects the position of the mobile unit by receiving and analyzing a signal transmitted by the mobile unit. .