Patent Publication Number: US-2005128081-A1

Title: Detecting system

Description:
TECHNICAL FIELD  
      The present invention relates to a detecting system sing a microwave radar or a millimeterwave radar, and also relates to a detecting system having a detecting area setting means and a calibration means of a radar. The detecting system is suitably used for a security monitoring system.  
     BACKGROUND ART  
      As a means for detecting a suspicious person intruding into indoor and/or outdoor sites and for giving an alarm, a detecting system using an infrared sensor such as that disclosed in Japanese Patent Laid-Open No. 2001-235367 has been widely used. In the use of the infrared sensor, a light emitting part and a light receiving part are installed at an entrance gate or an opening through which an suspicious person may intrude, and an abnormality can be detected by the light receiving part based on the detection/nondetection of the infrared light sent from the light emitting part, and then, an alarm signal is transmitted.  
      However, in the detecting system using the infrared  5  sensor, since the alarm signal is transmitted when the light flux of the infrared light is blocked, even in the case where a leaf or the like crosses over the light flux of the infrared light, the detecting system determines that an intruder crosses over it, and resulting in the error detection in many cases. Also, in the case where the detecting system using the infrared sensor is used in the outdoor environment, since the infrared light does not propagate under bad weather conditions such as fog and snow, the detecting system cannot be used in such a condition.  
      As a method for solving the above-mentioned problems, a detecting system using a radar using a radio wave with microwave bandwidth or millimeterwave bandwidth instead of the infrared sensor has been developed. In the detecting system using an infrared sensor, it is necessary to provide two devices such as a light emitting part and a light receiving part separately. However, in the case of using a radar as a means for detecting an intruder, the detection and monitoring of the intruder can be performed in the state where a transmitting antenna and a receiving antenna are set in a common case box. Therefore, the detecting system using a radar has a high flexibility in installation of the system in comparison to the detecting system using an infrared sensor.  
      In addition, in the detecting system using an infrared sensor, the simple information whether or not there exists an intruder is all that can be obtained. Meanwhile, in the detecting system using a radar, since it is possible to obtain the surface information of an intruding object, the possibility of the error detection can be extremely reduced.  
      Therefore, the detecting system using a radar can achieve improved performance in comparison to the detecting system using an infrared sensor.  
      Furthermore, in the detecting system using a radar, the propagation property of the radio wave is little influenced even under bad weather conditions such as fog and snow. Therefore, the detecting system using a radar has improved reliability in comparison to the detecting system using an infrared sensor.  
      As described above, the detecting system using a radar has various advantages in comparison to the detecting system using an infrared sensor.  
      However, the size and shape of the area to be monitored are changed depending on the case. In this respect, since only the one-dimensional information whether the infrared light from the light emitting part can be detected at the light receiving part or not can be obtained in the case of the infrared sensor, the installation of the light emitting part and the light receiving part itself determines the area to be monitored. On the other hand, in the case of a radar, a detectable area of the radar is a fan-shaped area principally determined by the maximum detecting distance and the maximum detecting angle which depend on the performance of a transmitting antenna of the radar. Thus, in such a case where the detectable area of the radar is larger than the area to be monitored, the detecting system may detect a person or the like passing outside the monitoring area and give an alarm therefor.  
     DISCLOSURE OF THE INVENTION  
      A typical aspect of the present invention is a detecting system which is provided with a radar for detecting a detecting object; a notification device for notifying the detection of the detecting object; a signal processing unit for controlling the notification device based on the signal sent from the radar; and a detecting area setting device for setting a range of the detecting area.  
      Another typical aspect of the present invention is a detecting system which is provided with a millimeterwave radar or microwave radar for detecting a monitoring object; an alarm device for notifying the detection of the monitoring object; a signal processing unit for processing a signal received by the radar and sending an operating signal to the alarm device; and a monitoring area setting device for setting a monitoring area of the monitoring object, wherein the signal processing unit controls the alarm device so as to give an alarm when the monitoring object exists inside the monitoring area and so as not to give an alarm when the monitoring object is outside the monitoring area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagram showing a preferred embodiment of the present invention;  
       FIG. 2  is a diagram showing another preferred embodiment of the present invention;  
       FIG. 3  is a diagram showing a configuration of a radar unit and an alarm device according to an embodiment of the present invention shown in  FIG. 1 ;  
       FIG. 4  is a diagram showing a configuration of a radar unit and an alarm device according to an embodiment of the present invention shown in  FIG. 2 ;  
       FIG. 5  is a diagram showing a circuit configuration in a radar module of the present invention;  
       FIG. 6  is a diagram showing another circuit configuration in a radar module of the present invention;  
       FIG. 7  is a flow chart showing an operational flow in the embodiment of the present invention shown in  FIG. 1 ;  
       FIG. 8  is a flow chart showing an operational flow in the embodiment of the present invention shown in  FIG. 2 ;  
       FIG. 9  is a waveform chart showing the state of the transmitting wave and the receiving wave in the dual frequency CW method;  
       FIG. 10  is a waveform chart showing the state of the transmitting wave and the receiving wave in the FMCW method;  
       FIG. 11  is a drawing illustrating shapes of reflectors used in the present invention. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
      For further understanding of the present invention, the present invention will be described with reference to the accompanying drawings.  
       FIG. 1  shows a preferred embodiment of the present invention. A radar unit in which a radar module  1  and a signal processing unit  2  are combined is installed near the area to be monitored. In this case, the radar module  1  has a transmitting antenna for a transmitting microwave signal or a millimeterwave signal, a receiving antenna for a receiving microwave signal or a millimeterwave signal, and a radio frequency circuit mounted therein, and the signal processing unit  2  functions to detect a detecting object such as a suspicious object and to transmit an alarm activating signal. When the radar unit transmits the alarm activating signal, the alarm activating signal reaches an alarm means  10  via a cable  16 . The alarm means  10  gives an alarm according to the signal.  
      Note that the alarm means  10  can be set in a place where the radar unit is installed, or can be set in a managing center or the like in a remote place.  
      In this embodiment, the radar module  1  has a function as a radar. A detectable area  4  of a suspicious object is in the shape of a fan which is principally determined by the maximum detecting distance and the maximum detecting angle based on the performance of the transmitting antenna provided in the radar module  1 . In an actual case, however, the size and shape of the area are varied in which the intrusion of the suspicious object is to be monitored. Therefore, the detectable area of the radar unit and the area to be monitored do not always correspond to each other. Thus, in the present invention, a plurality of reflectors  3   a  are provided so as to surround the area to be monitored, thereby setting a monitoring area  5  monitored by the radar unit. The signal processing unit  2  includes a function to determine whether the suspicious object exists in the monitoring area  5  or out of the monitoring area  5 . More specifically, the suspicious object  6   a  exists in the monitoring area  5  as shown in  FIG. 1 , and the signal processing unit  2  transmits the alarm activating signal to the alarm means  10 . Meanwhile, the suspicious object  6   b  exists in the detectable area  4  of the radar unit but out of the monitoring area  5 . Therefore, the alarm activating signal is not transmitted to the alarm means  10 . In this embodiment, not only the detection of the existence of the suspicious object  6   a  but also the movement of the suspicious object  6   a  can be monitored and tracked.  
       FIG. 3  shows a block diagram of the signal processing unit  2  according to the embodiment of the present invention.  10  The reference numeral  1  denotes a radar module for transmitting/receiving microwave signals or millimeterwave signals, and reference numeral  13  denotes an A/D converter. Electric power is supplied to each of the components from a DC power supply unit  11 . The intermediate frequency (IF) signal is transmitted from the radar module  1  to the A/D converter  13  and is converted into the digital signal, and the digital signal is transmitted to a signal processor unit (MPU)  14 . The IF signal includes the information such as the distance between the detecting object and the radar unit and the relative speed, and thus, the signal processing of the IF signal makes it possible to obtain the coordinate position of the detecting object in the monitoring area  5 , the moving direction thereof with the passage of time, and the moving speed thereof. Then, as shown in  FIG. 1 , when it is determined that a suspicious object exists inside the monitoring area  5  as a result of the comparison between the positions of the reflectors  3   a  surrounding the monitoring area  5  and the position of the suspicious object (e.g., object  6   a ), then the alarm activating signal is transmitted to the alarm means  10  via the cable  16 .  
      The determination whether the alarm activating signal is transmitted or not is made through, for example, the  5  process shown in  FIG. 7 . There are two types of signals detected by the radar unit. That is, the signal from the reflector  3   a  and the signal from the detecting object (suspicious object) to be monitored. The coordinate values of the reflectors are calculated based on the signals from the  10  several reflectors  3   a , and the monitoring area surrounded by the reflectors  3   a  is determined. Also, the coordinate values of the detecting object are calculated based on the signal from the detecting object itself. Then, it is determined whether the coordinate values of the detecting object exist in  15  the monitoring area  5  by comparing these coordinate values. When it is determined that the detecting object is in the monitoring area  5 , an alarm is given. When it is not in the monitoring area  5 , no alarm is given and the signal from the detecting object is obtained again and the coordinate values thereof are recalculated.  
      Next, another embodiment of the present invention will be described with reference to  FIGS. 2, 4 , and  8 . In this embodiment, the area in which the intrusion of the monitoring object (suspicious object) is to be monitored is set in such a manner as follows. That is, a reflector  3   b  is moved along the outer periphery of the monitoring area when installing a radar unit, thereby setting a virtual monitoring area  50 . For the movement of the reflector  3   b , the reflector  3   b  may be carried by human hands, and the reflector  3   b  can be moved along the outer periphery by using the moving device attached to the reflector. The signal processing unit  2  includes a function to determine whether the suspicious object exists inside the virtual monitoring area  50  or outside thereof, and in the case where the suspicious object  6   a  inside the virtual monitoring area  50  is detected, the alarm activating signal is transmitted to the alarm means  10  via the cable  16 . Also, in the case of the suspicious object  6   b  outside the virtual monitoring area  50 , the alarm activating signal is not transmitted.  
      The block diagram of the signal processing unit  2  according to the embodiment is shown in  FIG. 4 . Similar to the configuration in the first embodiment shown in  FIG. 3 , the radar module  1 , the A/D converter  13 , and the signal processor unit (MPU)  14  are provided, and a memory means  20  is further provided. The memory means  20  is used when setting the virtual monitoring area  50 . More specifically, when setting the virtual monitoring area  50 , the reflector  3   b  is moved along the outer periphery of the monitoring area, and at this time, the coordinate information obtained from the moving reflector  3   b  is accumulated in the memory means  20 . The virtual monitoring area  50  is set based on the coordinate information thus accumulated. When monitoring the movement of the suspicious object by using the radar unit, the obtained coordinates of the suspicious object and the virtual monitoring area  50  stored in the memory means  20  are compared, and the determination is made by the MPU  14  whether the suspicious object exists inside or outside the virtual monitoring area  50 .  
      The series of operations are performed according to the flow chart shown in  FIG. 8 . The operation in this embodiment includes two modes such as a process for setting the virtual monitoring area  50  and an operation for the actual monitoring. In the process for setting the area, the coordinate values of the reflector  3   b  moving along the outer periphery of the area to be monitored are calculated by using the signals transmitted from the reflector  3   b , and the obtained coordinate data is accumulated in the memory means  20 . The series of processes are repetitively performed until all of the area to be monitored is surrounded. In the operation for the monitoring, the coordinate values of the detecting object (suspicious object) to be monitored are calculated by using the signals transmitted from the object itself. Then, the coordinate values thus obtained and the coordinate data of the virtual monitoring area  50  accumulated in advance in the memory means  20  are compared with each other, thereby determining whether the coordinate values of the detecting object are inside the virtual monitoring area  50  or not. When the object is inside the monitoring area, an alarm is given. Also, when not inside the monitoring area, no alarm is given and the signal from the detecting object to be monitored is obtained again and the coordinate values thereof are recalculated.  
      Examples of outer appearances of the reflectors  3   a  and  3   b  provided or moved in order to define the monitoring area  5  and the virtual monitoring area  50 , are shown in  FIG. 11 . Each of the reflectors  3   a  and  3   b  comprises a reflection plate  30  and a pole  31  of the reflection plate  30 . A material capable of reflecting electric waves is used to form the reflection plate  30 , for example, the reflection plate  30  is made of metal. In the drawing, three types of the reflection plate  30  are exemplified. In  FIG. 11 ( a ), the reflection plate  30  is in the shape of a simple plate, and in  FIG. 11 ( b ), the reflection plate  30  is in the shape of a concave mirror so as to intensify the reflected signal. Also, in  FIG. 11 ( c ), the reflection plate  30  is in the shape of a polygonal pyramid (Though triangular pyramid is shown as an example, the shape thereof is not limited to this.).  
      Examples of the circuit configuration included in the radar module  1  of the radar unit used in the present invention are shown in  FIGS. 5 and 6 .  
      In the circuit shown in  FIG. 5 , the radar module  1  comprises a voltage-controlled oscillator (VCO)  23 , a power amplifier  24 , receivers  25   a  and  25   b , a transmitting antenna  22 , and two receiving antennas  21   a  and  21   b . Note that the receiving antennas  21   a  and  21   b  are arranged in the horizontal direction. The high frequency signal from the voltage-controlled oscillator  23  is transmitted from the transmitting antenna  22  via the power amplifier  24 . Then, the signal reflected at the object is received by the receiving antennas  21   a  and  21   b , and the signal thus received is inputted to the receivers  25   a  and  26   a  as an RF signal. The signal from the voltage-controlled oscillator  23  is also inputted to the receivers  25   a  and  25   b  as a local signal, and intermediate frequency (IF) signals IF 1  and IF 2  are generated from the RF signal and the local signal by mixers in the receivers  25   a  and  25   b . Then, the IF signals are transmitted to the A/D converter  13  provided in the signal processing unit  2 . The distance to the object and the relative speed are obtained based on the frequency of the IF signals, and the angle to the object in the horizontal direction is obtained based on the phase difference between the two IF signals.  
      In this embodiment, the case where two receivers are provided is shown. However, the detection accuracy in the horizontal direction can be enhanced by further increasing the number of the receivers.  
       FIG. 6  shows an example of the circuit in which each one of the receiving antenna  21  and the receiver  25  is provided. The operation of the circuit shown in  FIG. 6  is identical to that shown in  FIG. 5 . However, the circuit requires a device for periodically changing the directions of the transmitting antenna  22  and the receiving antenna  21  so as to detect the angle to the object in the horizontal direction. Both the signal indicating the direction of the antenna and the IF signal are transmitted to the A/D converter  13  provided in the signal processing unit  2 , thereby obtaining the distance to the object, the relative speed, and the angle in the horizontal direction.  
      The oscillation frequency of the voltage-controlled oscillator  23  included in the radar module  1  can be changed by changing the control voltage, and the distance to the object and the relative speed can be obtained by using the function.  
      An example of a sweeping method of a frequency applicable to the present invention is shown in  FIGS. 9 and 10 . In both of  FIGS. 9 and 10 , the horizontal axis of the graph represents time, and the vertical axis thereof represents frequency.  FIG. 9  shows the dual frequency CW (Continuous Wave) method, in which two frequency signals are regularly switched. The transmitting signal TX and the receiving signal RX are in a state as shown in  FIG. 9 , and the distance to the object can be determined from the time difference between TX and RX (difference in the lateral direction of the graph), and the relative speed of the object can be determined from the frequency difference (difference in the longitudinal direction of the graph).  FIG. 10  shows the Frequency Modulated Continuous Wave (FMCW) method, in which the interval between the two frequencies is continuously changed. Similar to the above-described dual frequency CW method, also in the FMCW method, the distance to the object can be determined from the time difference between TX and RX, and the relative speed of the object can be determined from the frequency difference.  
      Note that in such a case where the relative speed of the object is 0 (in a stationary state), the dual-frequency CW method cannot detect the object because the intermediate frequency (IF) generated by the receiver comes to 0 hertz. Meanwhile, even in such a case where the relative speed of the object is 0, the FMCW method can detect the object because the intermediate frequency does not come to 0 hertz.  
      In addition, the calibration of the radar unit and the self diagnosis thereof can be performed by using at least one of the reflectors  3   a  and  3   b  used in the embodiment of the present invention.  
      For example, the operation program is set so as to calculate the coordinate value of the reflectors  3   a  and  3   b  by use of the signals from the reflectors  3   a  and  3   b  at a constant interval, and then an adjustment means functioning to compare the calculated coordinate values and the actual positions of the reflectors  3   a  and  3   b  and to make an adjustment to eliminate the difference therebetween is provided. By doing so, the detection accuracy of the radar unit can be maintained in an optimal state.  
      Also, if the self-diagnosis means is provided, when the signals from the reflectors are not detected or the signal intensity is extremely reduced, it is possible to determine that there is something wrong with the function of the radar unit and also to give an alarm to the user. Note that the calibration means and the self-diagnosis means of the radar unit can be operated automatically or can be operated at any suitable time depending on the intention of the user.  
      The advantages obtained by the present invention are as follows.  
      First, in the detecting system using a radar, since the detection and monitoring of an intruder can be performed while a transmitting antenna and a receiving antenna are provided in a common case box, the flexibility in installing the detecting system can be improved.  
      Second, since surface information of an intruding object can be obtained in the detecting system using a radar, the possibility of the error detection is extremely reduced and the performance thereof can be enhanced.  
      Third, since there is little impact on the propagating property of the electric wave even under bad weather conditions such as fog and snow in the detecting system using a radar, the reliability thereof can be enhanced.  
      Fourth, since the detecting area of the radar can be set, the error detection that an alarm is given in response to the detected object outside the area where the existence of a suspicious object is monitored can be prevented.  
      Fifth, since the calibration and self diagnosis of the radar unit can be performed by use of the reflectors, the reliability of the detecting system can be obtained.  
     Industrial Applicability  
      The present invention relates to a detecting system using a microwave radar or a millimeter radar, which is suitably used as a security monitoring system to detect the existence of a suspicious person and to give an alarm when there exists a suspicious person.