JP2001004737A - Monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a monitoring system in which constitution can be simplified. SOLUTION: This monitoring system is equipped with two monitoring apparatuses L1, L2, which transmit communication waves toward an object A to be monitored. In this case, the monitoring apparatuses L1, L2 make only the transmitting timing of the communication waves synchronous. Consequently, the object A to be monitored detects at least two points as gauge marks, so that detection of existing positions of the monitoring apparatuses L1, L2 can be prevented. Since the monitoring apparatuses L1, L2 make only the transmitting timing of the communication waves synchronous, it is unnecessary to install a phase synchronizing circuit as in the case that a synthesized wave is formed. As a result, constitution of the monitoring apparatuses L1, L2 can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monitoring system for monitoring a counterpart monitoring device and the like.

[0002]

2. Description of the Related Art In a conventional monitoring system, one monitoring device is installed on the ground, and the presence of the monitored object is detected by receiving a communication wave from the monitored object such as a counterpart monitoring device. On the other hand, the monitored object generally has a plurality of sensors arranged to receive communication waves from different directions. Therefore, the monitored object can detect the source of the communication wave, that is, the location of the monitoring device from the arrival direction of the communication wave received by each sensor. Therefore, the monitoring device may be found in the monitored object.

A technique for coping with this is disclosed, for example, in Japanese Patent Application Laid-Open No. 5-45445. According to the technique disclosed in this publication, two radars are arranged at different positions, a combined wave is created in each radar, and the created combined wave is radiated to a flying object that is a monitored object. According to this technique, it is determined that the frequency of the pulse received by the flying object is the same. Therefore, it can be expected that the flying object will erroneously recognize a point different from the installation position of the two radars as the radio wave generating source.

[0004]

However, in the technique disclosed in the above-mentioned publication, since a composite wave is created using two radars, both the phase and the transmission timing of each radar wave are changed. Synchronized. in this case,
In order to synchronize the phases, it is necessary to provide a reference signal serving as a phase reference to the radar. Therefore, each radar must have a circuit for receiving the reference signal and a circuit for actually synchronizing the phase. Therefore, there is a problem that the configuration of the radar is complicated.

Therefore, an object of the present invention is to provide a monitoring system whose configuration can be simplified.

[0006]

According to the present invention for achieving the above object, a plurality of monitoring devices for transmitting a communication wave toward a monitored object are installed at different positions, and communication is performed from each of the monitoring devices. Waves are transmitted by synchronizing only the transmission timing.

[0007]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

Embodiment 1 FIG. 1 is a conceptual diagram showing a configuration of a monitoring system according to Embodiment 1 of the present invention. This monitoring system is for monitoring an object to be monitored. The monitored object is a monitoring system of the other party. This monitoring system includes a plurality of monitoring devices L1 and L2 (hereinafter, collectively referred to as “monitoring device L”). Each monitoring device L1, L2 is installed at a different position on the ground. The monitoring device L has a function of transmitting a communication wave.
Further, the monitoring device L detects the monitored object A by receiving the communication wave emitted from the monitored object A.

On the other hand, the monitored object A generally has a function of detecting a source of a communication wave. That is, the monitored object A
Includes a sensor device 1 and a computing unit 2. The sensor device 1 includes two sensors, a first sensor 1a and a second sensor 1b. First sensor 1a and second sensor 1b
Are provided at positions spatially separated from the monitored object A. The first sensor 1a and the second sensor 1b are, for example, antennas having directivity in a plurality of directions. Each of the first sensor 1a and the second sensor 1b receives a communication wave and obtains a direction of arrival of the received communication wave. Specifically, the first sensor 1a and the second sensor 1b
Is used to determine the direction of arrival of a radio wave using a conventionally known interferometer method, MUSIC method, or the like.

The arithmetic unit 2 detects the source of the communication wave, that is, the position of the monitoring device L, based on the radio wave arrival directions obtained by the first sensor 1a and the second sensor 1b, respectively. More specifically, the arithmetic unit 2 includes the monitoring device L
Is detected by the two-point intersection method. In the two-point intersection method, an intersection of two radio wave arrival directions is obtained.

As described above, the monitored object A has a plurality of sensors including the first sensor 1a and the second sensor 1b provided at different positions, thereby detecting the position of the monitoring device as a radio wave generating source. can do. on the other hand,
When the position of the monitoring device L is detected, the monitoring device L may not be able to function as a monitoring device. Therefore,
In the first embodiment, only the transmission timing of each communication wave transmitted from the two monitoring devices L1 and L2 is synchronized, thereby preventing the detection position of the monitoring device L from being detected.

FIG. 2 is a block diagram showing the internal configuration of the monitoring device L. The monitoring device L includes a transmitting unit 10 that transmits a communication wave, a receiving unit 11 that receives a communication wave emitted from the monitored object A, a data processing unit 12, and a timing control unit 1.
3 and GPS (Global Positioning System) receiver 14
And The data processing unit 12 obtains the direction of the monitored object A based on the communication wave received by the receiving unit 11. The GPS receiver 14 receives a GPS wave radiated from a GPS satellite traveling in orbit around the earth. The GPS wave includes accurate time information serving as a reference time. The GPS receiving unit 14 extracts time information from the received GPS wave, and supplies the extracted time information to the timing control unit 13 as reference time information. The timing control unit 13 controls the transmission unit 10 so as to synchronize the transmission timing of the communication wave with another monitoring device.

More specifically, the transmission timing control unit 1
3 includes a timing storage unit 13a. The timing storage unit 13a stores a transmission time at which a communication wave is transmitted. A plurality of the stored times are set at very accurate and fine intervals. The timing control unit 13 uses G
It is determined whether or not the time indicated by the reference time provided from the PS receiver 14 matches the transmission time stored in the timing storage 13a. The timing control unit 13
If the times do not match, the communication wave is not transmitted. On the other hand, if the times match, the timing control unit 13 unconditionally controls the transmission unit 10 to start transmitting the communication wave. That is, the transmission unit 10 transmits a communication wave by synchronizing only the transmission timing with another monitoring device.

As described above, the monitoring devices L1 and L2 simultaneously transmit communication waves by the operation of the timing control unit 13. Therefore, the monitored object A includes the respective monitoring devices L1,
Two communication waves transmitted from L2 will be received simultaneously. When the monitored object A receives two communication waves simultaneously, it operates as follows.

More specifically, referring to FIG. 1, the first sensor 1a and the second sensor 1b of the monitored object A are two sensors transmitted from two monitoring devices L1 and L2 at the same time. The communication waves W1 and W2 are received simultaneously. Therefore, the first sensor 1a has two communication waves W
1. The arrival directions D1 and D2 of W2 are simultaneously detected. Similarly, the second sensor 1b simultaneously detects the arrival directions D3 and D4 of the two communication waves W1 and W2. In this case, since the arithmetic unit 2 of the monitored object A obtains the control points by the two-point intersection method,
The two directions D1, D2 detected by the first sensor 1a and the second
Intersection E with two directions D2 and D4 detected by sensor 1b
1, E2, E3, and E4 are simultaneously obtained as control points.

In the arithmetic unit 2, the detected 4
It is also conceivable to narrow down the control points by appropriately combining the three directions D1 to D4. Specifically, the arithmetic unit 2 calculates (D1,
When D3) and (D2, D4) are selected, intersections E1 and E2 are detected as control points. In addition, arithmetic unit 2
When (D2, D3) and (D1, D4) are selected, the intersections E4 and E3 are detected as the control points. Further, the arithmetic unit 2 calculates (D1, D3) and (D1, D4)
Is selected, the intersections E1 and E3 are detected as the control points. Furthermore, when (D2, D3) and (D2, D4) are selected, the arithmetic unit 2 detects the intersections E4 and E2 as the control points. Further, the arithmetic unit 2 calculates (D
When (1, D4) and (D2, D4) are selected, intersections E3 and E2 are detected as control points. Furthermore,
When selecting (D1, D3) and (D2, D3), the arithmetic unit 2 detects intersections E1 and E4 as control points.

As described above, even when the detected directions D1 to D4 are appropriately combined, the arithmetic unit 2 cannot narrow down the control points to one point, and detects two points as control points. become.

As described above, according to the first embodiment, 2
The two monitoring devices L1, L2 are installed, and each monitoring device L1, L2
By synchronizing the transmission timing of the communication wave transmitted from 2, at least two points in the monitored object A can be detected as control points. Since the monitored object A does not know that a plurality of monitoring devices are installed, if two control points are obtained, it is impossible to detect the position of the monitoring device. Therefore, detection of the position where the monitoring device L exists can be prevented.

Further, the monitoring device L synchronizes only the transmission timing, not the phase. Therefore, a circuit for receiving the phase reference signal and a phase synchronization circuit are not required. Therefore, a monitoring device having a simple configuration can be provided. Therefore, for example, a simple monitoring system can be constructed at low cost.

In the above description, a case where two monitoring devices L are installed is taken as an example. However, it goes without saying that, for example, three or more monitoring devices L may be installed, and only the transmission timing of the communication wave transmitted from each of them may be synchronized.

Embodiment 2 FIG. FIG. 3 is a conceptual diagram showing a configuration of a monitoring system according to Embodiment 2 of the present invention. 3, the same reference numerals are used for the same functional parts as in FIG.

In the first embodiment, the two monitoring devices L
No particular mention is made of the arrangement positions of 1, L2. On the other hand, in the second embodiment, two monitoring devices L are arranged on substantially the same straight line for each of the first sensor 1a and the second sensor 1b, which are the two sensors of the monitored object A. Have been placed.

More specifically, in this monitoring system,
The three monitoring devices L1, L2, L3 are arranged in a triangular shape in plan view. More specifically, the first sensor 1
a and three monitoring devices L1 so that the directions of arrival of at least two communication waves are the same as viewed from the second sensor 1b.
L2 and L3 are arranged. In other words, the monitored object A
Monitoring device L along the same direction as viewed from the first sensor 1a.
1, L3, and the second sensor 1b of the monitored object A
The monitoring devices L2 and L3 are arranged along the same direction as viewed from above. That is, at least two monitoring devices are arranged along the same direction when viewed from both the first and second sensors 1a and 1b of the monitored object A. This is because the first and second sensors 1a, 1a,
This is for transmitting two communication waves to b from the same direction. The direction in which the sensors 1a and 1b of the monitored object A exist can be checked by, for example, a preliminary investigation.

In such a state, communication waves W1, W2, W transmitted from the three monitoring devices L1, L2, L3.
All three transmission timings are synchronized. In this case, the monitored object A receives three communication waves W1, W2, and W3 whose transmission timings are synchronized at the same time. On the other hand, the first sensor 1a of the monitored object A detects two arrival directions, that is, a first direction D1 and a second direction D2, as the arrival directions of the three received communication waves W1, W2, W3. In addition, the second sensor 1b of the monitored object A detects two arrival directions, that is, the third direction D3 and the fourth direction D4, as the arrival directions of the three received communication waves W1, W2, W3.

Originally, three communication waves W1, W2, W
Upon receiving 3, the monitored object A should detect three directions of arrival. However, the first and second sensors 1a,
1b respectively represent two communication waves W having the same arrival direction.
1, W3 and W2, W3 are received simultaneously. Therefore, the first sensor 1a detects one arrival direction, that is, the first direction D1, as the arrival directions of the two communication waves W1 and W3. Further, the second sensor 1b has two communication waves W2,
One arrival direction, that is, the third direction D3 is detected as the arrival direction of W3.

As described above, the computing unit 2 of the monitored object A is
Since the control points are obtained by the two-point intersection method, four directions D1
Four intersections E1 to E4 of D4 to D4 are obtained as control points.
Further, even when the arithmetic unit 2 determines the control points in consideration of the combination of the directions D1 to D4, as in the case of the first embodiment, six sets of patterns including two control points are detected as control points. I do. Therefore, even in the case of the second embodiment, similarly to the case of the first embodiment, detection of the position where the monitoring device L exists can be prevented.

Further, two monitoring devices L1, L3 and L2, L3 are arranged along the same direction as viewed from the first and second sensors 1a, 1b of the monitored object A, respectively.
Therefore, as a configuration of the monitored object A, the directions D1 to D4
Is the case where the photo control point is calculated in consideration of the combination of
Further, even in a case where two existing positions are detected by detecting two control points, it is possible to prevent the detection of the existing position of at least one monitoring device L. In other words, the monitored object A cannot detect three communication waves coming from three directions, and therefore cannot simultaneously detect three control points. Therefore, detection of the position of the monitoring device L can be more effectively prevented.

In addition, as in the first embodiment, only the transmission timings of the communication waves from the three monitoring devices L1, L2, L3 are synchronized, so that the circuit for receiving the phase reference signal and the phase synchronization circuit It becomes unnecessary. Therefore, a monitoring device having a simple configuration can be provided. Therefore, for example, a simple monitoring system can be constructed at low cost.

The arrangement pattern of the monitoring device L may be a pattern as shown in FIGS. 4, 5 and 6, for example. Further, the arrangement pattern of the monitoring devices L is, for example, as shown in FIG. 7, the four monitoring devices L1 and L
A pattern in which 2, L3, and L4 are arranged in a diamond shape in plan view may be used. In short, in any of the arrangement patterns shown in FIGS. 4 to 7, when viewed from the first sensor 1 a and the second sensor
More than one monitoring device may be installed.

Another embodiment. Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments. For example, in the above embodiment, time information in a GPS wave transmitted from a GPS satellite is used to synchronize transmission timings of communication waves transmitted from a plurality of monitoring devices L. However, for example, an external device other than the GPS and capable of keeping accurate time may be provided, and the external device may provide time information to all the monitoring devices L.

Further, in the above embodiment, the case where the computing unit 2 of the monitored object A detects the position of the monitoring device L by the two-point intersection method is taken as an example. However, for example, even if the computing unit 2 of the monitored object A detects the position of the monitoring device L by the three-point intersection method, the computing unit 2 sets the control point to 1 by synchronizing the transmission timing of the communication wave. Since it is not possible to focus on points, it is possible to prevent the detection of the position where the monitoring device L exists, as in the above embodiment. Note that the three-point intersection method is a method of detecting, as a control point, a center of gravity of a triangle drawn by the results of measurement in three directions, or a point at which the sum of perpendicular vectors to each direction measurement line becomes zero.

[0032]

As described above, according to the present invention, only the transmission timings of communication waves transmitted from a plurality of monitoring devices are synchronized, so that a phase receiving circuit and a phase synchronization circuit are not required. Therefore, a monitoring device having a simple configuration can be provided. Therefore, for example, a low cost, simple monitoring system can be constructed.

When two or more monitoring devices are installed so as to be in the same direction as viewed from a plurality of sensors provided on the monitored object, the arrival directions of two communication waves are one. Can be mistaken for the monitored object. Therefore, the detection of the position where the monitoring device exists can be prevented more favorably.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram illustrating a configuration of a monitoring system according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of the monitoring device.

FIG. 3 is a conceptual diagram illustrating a configuration of a monitoring system according to a second embodiment of the present invention.

FIG. 4 is a conceptual diagram showing a modification of the monitoring system according to the second embodiment.

FIG. 5 is a conceptual diagram illustrating a modified example of the monitoring system according to the second embodiment.

FIG. 6 is a conceptual diagram illustrating a modified example of the monitoring system according to the second embodiment.

FIG. 7 is a conceptual diagram illustrating a modification of the monitoring system according to the second embodiment.

[Explanation of symbols]

L, L1, L2, L3, L4 monitoring device, A monitored object, 1a first sensor, 1b second sensor, 2 computing unit, 10 transmission unit, 13 timing control unit, 13a
Timing storage unit, 14 GPS receiving unit.

Claims (3)

[Claims] 1. A plurality of monitoring devices for transmitting a communication wave toward a monitored object are installed at different positions, and the monitoring device transmits the communication wave only in synchronization with the transmission timing. A monitoring system characterized by the following. 2. The apparatus according to claim 1, wherein at least two monitoring devices are provided in a plan view for each of the plurality of sensors provided at different positions of the monitored object for detecting the arrival direction of the communication wave. A monitoring system characterized by being arranged on substantially the same straight line. 3. A communication wave transmitting unit for transmitting a communication wave, a storage unit for storing a time at which the communication wave is to be transmitted, a time obtaining unit for obtaining a reference time from an external device, A determination unit that determines whether or not the reference time thus set and the transmission time stored in the storage unit match; and if the determination unit determines that the reference time and the transmission time match, unconditionally Controlling the communication wave transmitting unit,
A transmission control unit for transmitting a communication wave.