Abstract:
Provided is a device for detecting intruding objects that enables the detection of intruding objects without requiring antenna switching. Delay units ( 102 ) use different delay amounts to delay signals received at each of a plurality of antennas ( 110 ). A signal synthesis unit ( 103 ) synthesizes the delayed signals. A frequency conversion unit ( 106 ) converts the synthesized signal frequency to a baseband. A wave detection unit ( 107 ) detects the signal that has undergone frequency conversion. A radar profile generation unit ( 104 ) uses the detected signal to generate a profile formed from the distance from the antenna, and the signal strength at each distance from the antenna. A detection processing unit ( 105 ) detects a peak in the profile at which the signal strength exceeds a preset threshold value, and determines whether an intruding object is present in a detection region on the basis of the detected peak.

Description:
TECHNICAL FIELD 
     The present invention relates to an intruding object detection apparatus and an intruding object detection method. 
     BACKGROUND ART 
     Conventionally, intruding object detection apparatuses using a millimeter wave radar have been proposed for the purpose of detecting an intruding object in a region such as the interior of the crossing of a railroad. 
     For example, in Patent Literature (hereinafter, abbreviated as PTL) 1, an antenna and a reflective reference point of a radar are placed in a predetermined position of the region for detection, and a detection processing section determines existence of an intruding object on the basis of the relationship between a reflected wave (measurement reflected wave) measured and a reflected wave from the reflective reference point. 
     Moreover, in PTL 1, two or more reflective reference points and antennas are placed so as to eliminate any region in which an intruding object cannot be detected (non-detected region) in a region for detection, such as a crossing, and the intruding object is detected over the whole region for detection by suitably switching the antenna which receives a signal inputted into the detection processing section. 
     CITATION LIST 
     Patent Literature 
     PTL1 
     Japanese Patent Application Laid-Open No. 2005-233615 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the case of switching the antenna which receives a signal inputted into the detection processing section like above-mentioned PTL 1, the omission in detection of the intruding object may occur depending on timing of switching the antenna and a place in which or timing at which the object intrudes into the region for detection. Moreover, PTL 1 needs a processing section for switching the antenna receiving a signal inputted into the detection processing section, and leads an increase in cost of the intruding object detection apparatus. 
     It is an object of the present invention to provide an intruding object detection apparatus and an intruding object detection method that can detect an intruding object without the need for switching of antennas. 
     Solution to Problem 
     An intruding object detection apparatus according to an aspect of the present invention is an apparatus that detects intrusion of an object into a region for detection, the apparatus including: an input section that receives signals reflected by a same object existing in the region for detection, using at least two respective antennas among a plurality of antennas; a delay section that delays the signals received respectively using the plurality of antennas using delay amounts that are different from each other, a combining section that combines the delayed signals; a frequency conversion section that frequency-converts the resultant combined signal into a baseband; a detection section that detects the frequency-converted signal; a generation section that generates a profile including distances from the antennas and signal intensity for each of the distances from the antennas using the detected signal; and a detection process section that detects a peak having the signal intensity exceeding a predetermined threshold in the profile and judges whether an intruding object exists in the region for detection based on the detected peak. 
     An intruding object detection method according to an aspect of the present invention is a method for detecting intrusion an object into a region for detection, the method including: receiving signals reflected by a same object existing in the region for detection, using at least two respective antennas among a plurality of antennas; delaying the signals received using the plurality of antennas using delay amounts that are different from each other, combining the respective delayed signals; frequency-converting the resultant combined signal into a baseband; detecting the frequency-converted signal; generating a profile including distances from the antennas and signal intensity for each of the distances from the antennas using the detected signal; and detecting a peak having the signal intensity exceeding a predetermined threshold in the profile, and judging whether an intruding object exists in the region for detection based on the detected peak. 
     Advantageous Effects of Invention 
     The present invention can detect an intruding object without the need for switching of antennas. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a block diagram illustrating a configuration of an intruding object detection system according to Embodiment 1 of the present invention; 
         FIG. 2  illustrates an example of an intruding object detection region according to Embodiment 1 of the present invention; 
         FIG. 3  illustrates an example of the intruding object detection region according to Embodiment 1 of the present invention; 
         FIG. 4  is a block diagram illustrating a configuration of an intruding object detection apparatus according to Embodiment 1 of the present invention; 
         FIG. 5  illustrates an intruding object detection boundary and the receiving regions of respective receiving antennas according to Embodiment 1 of the present invention; 
         FIG. 6  explains an intruding object detection process according to Embodiment 1 of the present invention; 
         FIG. 7  illustrates an example of a radar profile according to Embodiment 1 of the present invention; 
         FIG. 8  explains a peak detection process according to Embodiment 1 of the present invention; 
         FIG. 9  explains the intruding object detection process according to Embodiment 1 of the present invention; 
         FIG. 10  explains the peak detection process according to Embodiment 1 of the present invention; 
         FIG. 11  is a block diagram illustrating a configuration of an intruding object detection apparatus according to Embodiment 2 of the present invention; 
         FIG. 12  illustrates an intruding object detection boundary and the receiving regions of respective receiving antennas according to Embodiment 2 of the present invention; 
         FIG. 13  is a flow diagram illustrating the flow of a generation process on object positioning information according to Embodiment 2 of the present invention; 
         FIG. 14  explains a peak detection process according to Embodiment 2 of the present invention; 
         FIG. 15  explains the peak detection process according to Embodiment 2 of the present invention; and 
         FIG. 16  explains the peak detection process according to Embodiment 2 of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The embodiments of the present invention will be described in detail with reference to the accompanying drawings. In embodiments, the same components are designated with the same reference signs, and repetitive explanations thereof will be omitted. 
     Embodiment 1 
     Configuration of Intruding Object Detection System 
       FIG. 1  illustrates a main configuration of intruding object detection system  10  according to Embodiment 1 of the present invention. Intruding object detection system  10  includes intruding object detection apparatus  100 , n receiving antennas  110 - 1  to  110 - n , transmission signal generation section  200 , and transmitting antenna  210 . 
     In  FIG. 1 , intruding object detection apparatus  100  detects intrusion of an object into an “intruding object detection region” on the basis of a reflected wave (signal reflected at the intruding object) of a transmission signal emitted from transmitting antenna  210 . Transmission signal generation section  200  generates a pulse and periodically emits the generated pulse (transmission signal) towards the “intruding object detection region” through transmitting antenna  210 . Moreover, transmission signal generation section  200  reports timing of periodically emitting a transmission signal to intruding object detection apparatus  100 . 
     Here, the “intruding object detection region” refers to a region that is targeted for detection of an intruding object and that is surrounded by the boundary of the region for detection (hereinafter referred to as “intruding object detection boundary”) and the point of mounting intruding object detection system  10 . For example,  FIG. 2  and  FIG. 3  illustrate examples of mounting intruding object detection system  10 . 
       FIG. 2  illustrates the example of mounting intruding object detection system  10  in the crossing of a railroad. In  FIG. 2 , intruding object detection system  10  is a system detecting an object intruding into a crossing. That is, in  FIG. 2 , the “intruding object detection boundary” is represented as a line segment connecting one endpoint  10 A of the crossing and endpoint  10 B on the other side. The “intruding object detection region” is represented as a region surrounded by a line segment connecting the point of mounting intruding object detection system  10 , endpoint  10 A, and endpoint  10 B. 
       FIG. 3  illustrates the example of mounting intruding object detection system  10  in the platform of a station of a railroad. In  FIG. 3 , intruding object detection system  10  is a system detecting an object intruding from the platform into a railway track. That is, in  FIG. 3 , the “intruding object detection boundary” is represented as a line segment connecting one endpoint  10 A of the boundary between the platform and the railway track, and endpoint  10 B on the other side. The “intruding object detection region” is represented as a region defined by a line segment connecting the point of mounting intruding object detection system  10 , endpoint  10 A, and endpoint  10 B. 
     Transmitting antenna  210  is mounted and designed so that the entire intruding object detection region described above can be covered. For example, the directivity direction (the center of the emission direction) of transmitting antenna  210  is designed so as to be directed towards the center (the midpoint of endpoint  10 A and endpoint  10 B illustrated in  FIG. 2  or  FIG. 3 ) of intruding object detection region. Moreover, the half-value angle of transmitting antenna  210  is designed on the basis of the angle defined by endpoint  10 A, intruding object detection system  10 , and endpoint  10 B. Thereby, transmitting antenna  210  periodically emits a transmission signal towards the entire intruding object detection region. 
     Configuration of Intruding Object Detection Apparatus 
       FIG. 4  illustrates a configuration of intruding object detection apparatus  100  according to Embodiment 1 of the present invention. In  FIG. 4 , intruding object detection apparatus  100  has reflected wave input section  101 , delay section  102 , signal combining section  103 , frequency conversion section  106 , orthogonal detection section  107 , radar profile generation section  104 , and detection processing section  105 . 
     According to the number of receiving antennas  110  (n antennas in  FIG. 4 ), two or more reflected wave input sections  101  and two or more delay sections  102  (n antennas in  FIG. 4 ) are provided. Specifically, reflected wave input section  101 - 1  and the delay section  102 - 1  are provided corresponding to receiving antenna  110 - 1 , and reflected wave input section  101 - n  and delay section  102 - n  are provided corresponding to receiving antenna  110 - n.    
     Reflected wave input sections  101  respectively receive reflected waves from an object receiving transmission signals emitted from transmitting antennas  210  as received signals, through corresponding receiving antennas  110 . Reflected wave input section  101  outputs the received signal to delay section  102 . 
     Respective delay sections  102  delay received signals inputted from corresponding reflected wave input sections  101 , using delay amounts that are different from each other. For example, delay section  102  may generate delay by including a transmission line or a delay element in its inside. 
     As illustrated in  FIG. 4 , each delay section  102  is provided between corresponding reflected wave input section  101  and signal combining section  103  described below. In the present embodiment, respective delay sections  102  set the above-described delay amounts that are different from each other, so as to equalize path lengths between intersection points of the intruding object detection boundary and the directivity directions of respective receiving antennas  110 , and signal combining section  103  among multiple receiving antennas  110 . More specifically, respective delay sections  102  set the above-described delay amounts that are different for respective received signals inputted from reflected wave input sections  101 , so as to equalize path lengths after transmission signals are emitted from transmitting antenna  210  until received signals (reflected waves) reach signal combining section  103 , with respect to objects existing in respective intersection points of the intruding object detection boundary and the directivity directions of respective receiving antennas  110 . 
     Signal combining section  103  combines a received signal inputted from each delay section  102 , and outputs the combined received signal to frequency conversion section  106 . 
     Frequency conversion section  106  receives a signal in a high frequency band outputted from signal combining section  103 , down-converts the inputted signal in a high frequency band into a baseband, and outputs the down-converted signal to detection section  107 . 
     Detection section  107  detects the signal generated in transmission signal generation section  200 , from the baseband signal outputted by frequency conversion section  106 , and outputs the detected signal to radar profile generation section  104 . 
     Radar profile generation section  104  receives the signal outputted from detection section  107 , and receives information on emission timing of a transmission signal from transmission signal generation section  200  ( FIG. 1 ). Radar profile generation section  104  generates a radar profile using the emission timing of a transmission signal and the received signal. Here, a “radar profile” includes the distance of receiving antenna  110 , and reflective intensity (signal intensity) for each distance. 
     Specifically, radar profile generation section  104  first digitizes a signal outputted from detection section  107 . Then, radar profile generation section  104  calculates the cross-correlation of the digitized baseband signal and the transmission signal, and thereby specifies how long the received signal delays being received by reflected wave input section  101  from the emission timing of a transmission signal and how intense the received signal is. In this case, radar profile generation section  104  does not use a signal received in the period from the emission start of a transmission signal until the emission completion of the transmission signal for generation of a radar profile, and determines the length of the radar profile according to the transmitting cycle of the transmission signal. In this way, radar profile generation section  104  periodically generates a radar profile including the “distance” representing how long the received signal delays being received by reflected wave input section  101 , and “reflective intensity” representing how intense the received signal is for each distance, in synchronization with the transmitting cycle of a transmission signal. 
     Detection processing section  105  detects a peak of reflective intensity exceeding a predetermined threshold (threshold for boundary detection) in the radar profile inputted from radar profile generation section  104 , and judges whether an object intruding into the intruding object detection region exists on the basis of the detected peak. In the present embodiment, detection processing section  105  compares the signal intensity (reflective intensity) in the radar profile and the threshold, and judges that an object intruding into the intruding object detection region exists when detecting the signal intensity (peak) exceeding the threshold. When detecting existence of an intruding object, detection processing section  105  outputs information representing that the existence of the intruding object is detected. The information representing that the intruding object is detected may be outputted, for example, to a control apparatus (not illustrated), such as a traffic light control apparatus, and may be utilized. 
     Operations of Intruding Object Detection Apparatus  100   
     Operation of intruding object detection apparatus  100  having the above configuration will be explained. 
     In the following explanation, intruding object detection system  10  includes three receiving antennas  110 - 1 ,  110 - 2 , and  110 - 3  (that is, the case of n=3) as an example. However, the number of receiving antennas  110  is not limited to three and may be two or more. 
     How to Mount Receiving Antennas  110   
       FIG. 5  illustrates an example of how to mount receiving antennas  110 - 1  to  110 - 3 .  FIG. 5  illustrates a state of point  1  OH (mounting point of receiving antenna  110 ) of mounting intruding object detection system  10  and intruding object detection boundary  10 C viewed from the above. In this explanation, intruding object detection system  10  and receiving antenna  110  are integrated. However, intruding object detection system  10  and receiving antenna  110  do not need to be integrated. 
     Receiving antennas  110 - 1  to  110 - 3  each have the same property. In  FIG. 5 , the half-value angle of each of receiving antennas  110 - 1  to  110 - 3  is referred to as  10 G. Moreover, in  FIG. 5 , point  10 D on intruding object detection boundary  10 C is the intersection point of the directivity direction of receiving antenna  110 - 1  and intruding object detection boundary  10 C. Similarly, point  10 E on intruding object detection boundary  10 C is the intersection point of the directivity direction of receiving antenna  110 - 2  and intruding object detection boundary  10 C, and point  10 F on intruding object detection boundary  10 C is the intersection point of the directivity direction of the receiving antenna  110 - 3  and intruding object detection boundary  100 C. 
     As illustrated in  FIG. 5 , receiving antennas  110 - 1  to  110 - 3  are mounted towards intruding object detection boundary  10 C so as not to overlap the directivity direction of the antennas with each other. Furthermore, receiving antennas  110 - 1  to  110 - 3  are mounted so that each interval between the intersection points ( 10 D,  10 E, and  10 F) described above may be equal to or less than half of the width of the reflective surface of an object for intrusion detection. For example, as illustrated in  FIG. 5 , the interval between intersection points ( 10 D,  10 E) of intruding object detection boundary  10 C and respective directivity directions of receiving antenna  110 - 1  and receiving antenna  110 - 2  that have adjacent receiving regions is equal to or less than half of the width of the reflective surface (that is, the surface on which a transmission signal can be reflected) of the object for intrusion detection. 
     Accordingly, an object for intrusion detection existing on intruding object detection boundary  10 C always exists while straddling the insides of the receiving regions of two or more receiving antennas  110 . Thereby, reflected wave input section  101  receives a signal (reflected wave) reflected by the same object for intrusion detection existing in the intruding object detection region (in this case, on intruding object detection boundary  10 C) with each of at least two receiving antennas  110  among multiple receiving antennas  110 . 
     Delay Process 
     In  FIG. 5 , the distance between point  10 H and point  10 D is referred to as distance A, the distance between point  10 H and point  10 E is distance B, and the distance between point  10 H and point  10 F is distance C. In this case, delay section  102  corresponding to each receiving antenna  110  sets a delay amount added to a received signal on the basis of the difference between distances A, B, and C. 
     For example, a case will be explained where the delay amount in delay section  102 - 3  corresponding to receiving antenna  110 - 3  is set to 0 on the basis of receiving antenna  110 - 3 . 
     In this case, delay section  102 - 2  corresponding to receiving antenna  110 - 2  sets the delay amount corresponding the double of the difference between distance B and distance C. Similarly, delay section  102 - 1  corresponding to receiving antenna  110 - 1  sets the delay amount corresponding the double of the difference between distance A and distance C. 
     That is, delay sections  102 - 1  to  102 - 3  set the delay amounts according to the differences between the distances between receiving antennas  110 - 1  to  110 - 3  and the intersection points ( 10 D,  10 E,  10 F) corresponding to respective receiving antennas  110  on intruding object detection boundary  10 C, respectively. Thereby, the path lengths on which transmission signals (pulses) emitted from point  10 H illustrated in  FIG. 5  reflects on point  10 D, point  10 E, and point  10 F and reach signal combining section  103  through reflected wave input sections  101 - 1  to  101 - 3  and delay sections  102 - 1  to  102 - 3 , respectively, are equal among the multiple receiving antennas  110 . 
     Radar Profile Generation Process 
       FIG. 6  illustrates a case where intruding object  21  exists on intrusion detection boundary  10 C. Intruding object  21  is, for example, a vehicle. 
       FIG. 7  illustrates an example of a radar profile generated in radar profile generation section  104  in the state illustrating in  FIG. 6 . In  FIG. 7 , a horizontal axis represents a distance from mounting point  10 H of intruding object detection system  10 , and a vertical axis represents reflective intensity (namely, signal intensity of a received signal). As illustrated in  FIG. 7 , a reflected wave from intruding object  21  has a peak in distance  32 . 
     In  FIG. 6 , since intruding object  21  exists while straddling the insides of the receiving regions of receiving antennas  110 - 2  and  110 - 3 , reflected waves from intruding object  21  are received through receiving antennas  110 - 2  and  110 - 3  in two reflected wave input sections  101  that are reflected wave input sections  101 - 2  and  101 - 3 . In  FIG. 6 , a reflected wave from intruding object  21  on intruding object detection boundary  10 C received in reflected wave input section  101 - 2  arrives earlier than a reflected wave from intruding object  21  received in reflected wave input section  101 - 3 , by the double of the difference between distance B and distance C. Moreover, a delay amount is set as 0 in delay section  102 - 3 , and a delay amount corresponding to the double of the difference between distance B and distance C is set in delay section  102 - 2 . 
     Thereby, signal combining section  103  combines signals received in two reflected wave input sections  101 - 2  and  101 - 3 , as signals received through the same path length. Here, since receiving antenna  110 - 3  is set as the reference, signal combining section  103  combines a signal received in each of reflected wave input sections  101 - 2  and  101 - 3  as a signal received through the path between point  10 F and point  10 H illustrate in  FIG. 6 . In this manner, a radar profile generated in radar profile generation section  104  has a peak representing a state where signals received in two reflected wave input sections  101 - 2  and  101 - 3  are combined as signals through the same distance. That is, as illustrated in  FIG. 7 , the radar profile has one peak centering on distance  32  corresponding to point  10 F illustrated in  FIG. 6 . 
     Peak Detection Process 
     As described above, intruding object  21  on intruding object detection boundary  10 C illustrated in  FIG. 6  exists while straddling the inside of receiving regions of at least two receiving antennas  110 . Therefore, received signals received in multiple reflected wave input sections  101  corresponding to at least two receiving antennas  110  are combined in the same distance in the radar profile, and forms a peak. That is, in the case of a reflected wave from intruding object  21  on intruding object detection boundary  10 C, the amplitude of a peak (reflective intensity) appearing in the radar profile is larger than reflective intensity that can be taken by a reflected wave from intruding object  21  received in one receiving antenna  110 . 
     Consequently, detection processing section  105  sets a larger value than reflective intensity that can be taken by a reflected wave from the intruding object received in one receiving antenna  110 , as a threshold. For example, where the distance from reflected wave input section  101  is d, and a reflective cross section of an object targeted for detecting the intrusion is σ, threshold Th(d) may be set in a range satisfying the conditions of Expression 1.
 
[1]
 
 Th ( d )&gt; Kσ/d   4   (Expression 1)
 
     Here, K represents signal electric power and is a constant determined by, for example, the property of receiving antenna  110 . The value of the right side of expression 1 is considered as reflective intensity from an intruding object received by one reflected wave input section  101 . 
     Detection processing section  105  judges whether a peak having reflective intensity exceeding the threshold exists in the radar profile generated in radar profile generation section  104 . Specifically, detection processing section  105  judges that an intruding object exists in the intruding object detection region (here, on intruding object detection boundary  10 C), when detecting a peak having reflective intensity exceeding the threshold in the radar profile.  FIG. 8  illustrates threshold  40  (dashed line) for the radar profile illustrated in  FIG. 7 . In  FIG. 8 , detection processing section  105  detects a peak having reflective intensity exceeding the threshold in distance  32 , and detects that an intruding object exists in intruding object detection boundary  10 C. 
     Next, a case where intruding object  21  does not exist on intruding object detection boundary  10 C will be explained. For example,  FIG. 9  illustrates a case where the reflective surface of intruding object  21  exists in the intrusion detection region across intruding object detection boundary  10 C. Moreover,  FIG. 10  illustrates an example of a radar profile generated in radar profile generation section  104  in the state illustrating in  FIG. 9 . 
     As illustrated in  FIG. 10 , in radar profile generated when a reflected wave from intruding object  21  is received, peaks appear in two places, i.e., distance  31  and distance  33 . This is because the delay amounts set in respective delay section  102  are set so as to equalize the path lengths of signals reflected on intrusion detection boundary  10 C among receiving antennas  110 . That is, as illustrated in  FIG. 9 , with respect to reflected waves from intruding object  21  existing in the intrusion detection region across intrusion detection boundary  10 C top, path lengths until reaching signal combining section  103  differ for respective receiving antennas  110 - 1  to  110 - 3 . As a result, peaks corresponding to reflected waves received in respective reflected wave input sections  101 - 2  and  101 - 3  individually appear in the radar profile illustrated in  FIG. 10 . 
     That is, the amplitudes of peaks appearing in distances  31  and  33  illustrated in  FIG. 10  correspond to reflective intensity from the intruding object received by one reflected wave input section  101 . Therefore, since both of the peak in distance  31  and the peak in distance  33  are smaller than threshold  40  in  FIG. 10 , detection processing section  105  does not detect that an intruding object exists in intrusion detection boundary  10 C. 
     In this way, since a delay amount in delay section  102  is set using intruding object detection boundary  10 C as the reference, a peak exceeding threshold  40  is generated only in a reflected wave from an object on intrusion detection boundary region  10 C. Therefore, only when an intrusion detection object exists on intruding object detection boundary  10 C, detection processing section  105  can detect intrusion of the object. Accordingly, intruding object detection apparatus  100  can detect only the time of an intruding object intruding into intruding object detection boundary  10 C, without requiring a process of comparing the distance of a peak and the distance from the intruding object detection boundary. 
     According to the present embodiment, intruding object detection apparatus  100  can detect only intrusion of an object existing on intruding object detection boundary  10 C, as described above. Moreover, intruding object detection apparatus  100  receives reflected waves from an object for intrusion detection in at least two receiving antennas  110 , and thereby can detect intrusion of the object to intruding object detection boundary  10 C, without switching of receiving antennas  110 . Consequently, an intruding object can be detected without the need for switching of antennas. Moreover, in the present embodiment, since a processing section for switching of antennas is unnecessary, an increase in cost of intruding object detection apparatus  100  can be avoid. 
     In addition, when a peak having reflective intensity exceeding threshold  40  is detected in the radar profile, and when a distance in the radar profile corresponding to the detected peak (distance  32  in  FIG. 8 ) corresponds to the vicinity of intruding object detection boundary  10 C, detection processing section  105  may judge that an intruding object exists in intruding object detection boundary  10 C. That is, detection processing section  105  may compare a distance (distance  32  in  FIG. 8 ) corresponding to a peak exceeding threshold  40  and an actual distance to intruding object detection boundary  10 C (the distance between point  10 H and point  10 F in  FIG. 6 ), check that an object exists near intruding object detection boundary  10 C, and then output information representing that the intruding object is detected. 
     Moreover, the present embodiment has been explained in an example case where a vehicle is assumed as an intruding object. However, a person may be assumed as an object for intrusion detection, and the antenna directivity direction of receiving antenna  110  may be set based on the width of the person. With this configuration, even for an object, such as a person having a small width in comparison with a vehicle, reflected waves from the same object can be received in multiple reflected wave input sections  101 . Thus, intrusion of a person can be detected in the intruding object detection boundary like the present embodiment. Thereby, for example, the white line on the platform of the station illustrated in  FIG. 3  is set as a boundary (intruding object detection boundary), and this enables intruding object detection apparatus  100  to announce detection of an intruding object when a person intrudes across the white line into the railway track side. 
     Embodiment 2 
     In Embodiment 1, the receiving regions of the multiple receiving antennas included in the intruding object detection system are set so as not to overlap with each other. In contrast to this, the present embodiment will be explained in a case where the receiving regions of the multiple receiving antennas included in the intruding object detection system are set so as to overlap with each other. 
       FIG. 11  illustrates intruding object detection apparatus  300  according to Embodiment 2 of the present invention. In intruding object detection apparatus  300  illustrated in  FIG. 11 , the same elements as those in Embodiment 1 ( FIG. 4 ) are designated with the same reference signs, and repetitive descriptions thereon will be omitted. Specifically, intruding object detection apparatus  300  illustrated in  FIG. 11  involves different operations of detection processing section  301  and newly includes object positioning section  302 , in comparison with intruding object detection apparatus  100  illustrated in  FIG. 4 . Intruding object detection system  10  according to the present embodiment includes intruding object detection apparatus  300  instead of intruding object detection apparatus  100  illustrated in  FIG. 1 . 
     In intruding object detection system  10  according to the present embodiment, the antenna half-value angle of each of multiple receiving antennas  110  is set so as to overlap with the receiving region of another receiving antenna  110 . That is, multiple receiving antennas  110  are mounted so that at least two receiving antennas  110  may receive reflected waves from an object for intrusion detection. 
       FIG. 12  explains mounting conditions for receiving antennas  110  according to the present embodiment. In the following explanation, intruding object detection system  10  includes three receiving antennas  110 - 1 ,  110 - 2 , and  110 - 3  (that is, the case of n=3) as an example. 
     Receiving antenna  110 - 1 ,  110 - 2 , and  110 - 3  illustrated in  FIG. 12  have antenna half-value angles that are angle  93 , angle  94 , and angle  95 , respectively. Here, as illustrated in  FIG. 12 , the receiving region of each receiving antenna  110  overlaps with the receiving region of another receiving antenna  110 . For example, in  FIG. 12 , the region of approximately half of the receiving region of each receiving antenna  110  is mounted so as to overlap with the receiving regions of adjoining receiving antennas  110 . 
     Moreover, as illustrated in  FIG. 12 , receiving antennas  110  are mounted towards intruding object detection boundary  10 C so that regions not overlapping with the receiving region of any other receiving antennas  110  are set as the outside of a region for intruding object detection. In  FIG. 12 , a region not overlapping with the receiving region of receiving antenna  110 - 2  in the receiving region of receiving antenna  110 - 1  and a region not overlapping with the receiving region of receiving antenna  110 - 2  in the receiving region of receiving antenna  110 - 3  are set as the outside of a region for intruding object detection. That is, the intruding object detection region is set in a region where the receiving regions of at least two receiving antennas  110  of multiple receiving antennas  110  overlap with each other. 
     In this manner, any position in the intruding object detection region corresponds to the receiving region of at least two receiving antennas  110 . Therefore, intruding object detection apparatus  300  (reflected wave input section  101 ) receives respective waves reflected from the same object for intrusion detection in the intruding object detection region through at least two receiving antennas  110  of multiple receiving antennas  110  like Embodiment 1. 
     In intruding object detection apparatus  300  illustrated in  FIG. 11 , detection processing section  301  detects a peak exceeding a predetermined threshold in the radar profile generated in radar profile generation section  104  like Embodiment 1 (detection processing section  105 ). However, the threshold set in detection processing section  301  is set to a value smaller than reflective intensity that can be taken by a reflected wave received in one receiving antenna  110 . 
     In intruding object detection apparatus  300 , reflected waves from the same object are received by multiple receiving antennas  110 , and respective received signals are subject to delay processes involving different delay amounts. In this case, in signal combining section  103 , the reflected waves received with respective receiving antenna  110  have path lengths that differ corresponding to the differences in the delay amounts of the delay processes performed on respective received signals. That is, in a radar profile generated in radar profile generation section  104 , peaks corresponding to the reflected waves from the same object appear in the distances corresponding to the differences in the delay amounts in the delay processes performed on reflected waves received with respective receiving antennas  110 . That is, two peaks separated by the distance corresponding to the difference in delay amounts set in respective delay sections  102  represent peaks caused by the reflected waves from the same object. 
     Consequently, when detecting at least two peaks having reflective intensity exceeding the threshold in the radar profile, detection processing section  301  operates as follows. That is, when the distance difference between at least two detected peaks is equal to the distance corresponding to the difference in the delay amounts for reflected waves received with at least two specific receiving antennas  110  among multiple receiving antennas  110 , detection processing section  301  judges that an intruding object exists in the intruding object detection region. For example, in  FIG. 12 , examples of the distance corresponding to the difference in the delay amounts for reflected waves received with at least two specific receiving antennas  110  is given as follows. Such examples are given as the distance corresponding to the difference between the delay amount set in delay section  102 - 1  and the delay amount set in delay section  102 - 2 , and the distance corresponding to the difference between the delay amount set in delay section  102 - 2  and the delay amount set in delay section  102 - 3 . 
     When detecting existence of an intruding object, detection processing section  301  outputs information representing that the existence of the intruding object is detected. Moreover, detection processing section  301  outputs peak position information representing the distance corresponding to each detected peak, to object positioning section  302 . 
     Object positioning section  302  estimates the position (direction and distance) of the object existing in the intruding object detection region on the basis of the peak position information inputted from detection processing section  301  and the difference in the delay amounts set in respective delay sections  102 , and generates object positioning information representing the position of the object. 
     The information representing detection of the intruding object and the object positioning information obtained as described above may be outputted, for example, to a control apparatus (not illustrated), such as a traffic light control apparatus, and may be utilized. 
       FIG. 13  is a flow diagram illustrating an example of the flow of a generation process on object positioning information in object positioning section  302 . 
     In Step (hereinafter referred to as “S”)  101  in  FIG. 13 , object positioning section  302  retrieves one piece of unprocessed peak position information from the peak position information acquired from detection processing section  301 . Object positioning section  302  treats the retrieved peak position information as peak position information targeted for the process in S 102  and S 103  described below. 
     In S 102 , object positioning section  302  determines whether other peak position information exists that represents a distance separated by a distance corresponding to the difference in the delay amounts set in delay sections  102 , from a distance (distance from intruding object detection system  10 ) represented in the peak position information for the process. 
     When the other peak position information does not exist (S 102 : No), the process progresses to a process of S 104 . On the other hand, when the other peak position information exists (S 102 : Yes), object positioning section  302  in S 103  considers the other peak position information as peak position information corresponding to a reflected wave from the same object as an object corresponding to the peak position information for the process. 
     Consequently, when two pieces of peak position information exist that are separated by the distance corresponding to the difference in delay amounts set in respective delay sections  102  (S 102 : Yes), object positioning section  302  specifies the difference in delay amounts according to the distance difference between the peaks represented in the two pieces of peak position information. Thereby, object positioning section  302  estimates in which receiving region (the direction of the object) of receiving antenna  110  the object corresponding to the peak position information exists. Moreover, object positioning section  302  deducts the distance corresponding to the specified delay amount from the distance of the peak represented in the peak position information, and thereby estimates the actual distance from intruding object detection apparatus  300  to the object. Then, object positioning section  302  outputs object positioning information including the direction of the estimated object and the distance to the object, as an object positioning result. 
     In S 104 , object positioning section  302  determines whether unprocessed peak position information exists. When unprocessed peak position information exists (S 104 : Yes), the process returns to a process of S 101  again. When unprocessed peak position information does not exist (S 104 : No), the process is completed. 
     Next, an example case will be explained where an object intruding in the intruding object detection region exists in each position of object  90 , object  91 , and object  92  illustrated  FIG. 12 . In addition, threshold  41  illustrated in  FIG. 14  to  FIG. 16  is set to a value smaller than reflective intensity that can be taken by a reflected wave received in one receiving antenna  110 . 
       FIG. 14  illustrates an example of a radar profile when only object  90  exists in  FIG. 12 . 
     As described above, since different delay amounts are set in respective delay sections  102 , two or more peaks appear in the radar profile illustrated in  FIG. 14  even when only one object  90  exists in the intruding object detection region. Specifically, object  90  is located in a region where the receiving region of receiving antenna  110 - 1  overlaps with the receiving region of receiving antenna  110 - 2 , as illustrated in  FIG. 12 . As a result, the reflected wave from object  90  is inputted into reflected wave input section  101 - 1  and  101 - 2  through receiving antennas  110 - 1  and  110 - 2 , respectively. Moreover, the difference between distance  34  of one peak and distance  35  of the other peak illustrates  FIG. 14  is equal to the distance corresponding to the difference between the delay amount set in delay section  102 - 1  and the delay amount set in delay section  102 - 2 . 
     Therefore, since the distance difference between two peaks illustrated in  FIG. 14  is equal to the distance corresponding to the difference in the delay amounts set in respective delay sections  102 - 1  and  102 - 2 , detection processing section  301  judges that an intruding object exists in the intruding object detection region. 
     Moreover, since the distance difference in two peaks illustrated in  FIG. 14  is equal to the distance corresponding to the difference in the delay amounts set in respective delay sections  102 - 1  and  102 - 2 , object positioning section  302  estimates that an intruding object (object  90 ) exists in the direction of a region where the receiving region of receiving antenna  110 - 1  overlaps with the receiving region of receiving antenna  110 - 2 . Furthermore, object positioning section  302  estimates the distance to an intruding object (object  90 ) using distance  34  or distance  35  illustrated in  FIG. 14  and the delay amount set in delay section  102 - 1  or delay section  102 - 2 . For example, object positioning section  302  makes this estimation by assuming that the distance to an intruding object is given as a distance obtained by deducting the distance corresponding to the smaller delay amount (larger delay amount) among the delay amounts set in delay sections  102 - 1  and delay section  102 - 2  from distance  34  (distance  35 ). 
       FIG. 15  illustrates an example of a radar profile when only object  91  exists in  FIG. 12 . 
     As illustrated in  FIG. 12 , object  91  is located in a region where the receiving regions of respective receiving antennas  110 - 1  to  110 - 3  overlap. As a result, the reflected waves from object  91  are received in reflected wave input sections  101 - 1  to  101 - 3  through receiving antennas  110 - 1  to  110 - 3 , respectively. Moreover, the distance difference between respective peaks in the radar profile illustrated in  FIG. 15  is equal to the distance corresponding to the difference in the delay amounts set in respective delay sections  102 . 
     For example, it is assumed that the delay amount set in delay section  102 - 1  is the largest and that the delay amount set in delay section  102 - 3  is the smallest. In this case, among three peaks corresponding to reflected waves from the same object in the radar profile illustrated in  FIG. 15 , the distance of the peak corresponding to a reflected wave received through receiving antenna  110 - 1  is the longest (distance  38 ), and the distance of the peak corresponding to a reflected wave received through receiving antenna  110 - 3  is the shortest (distance  36 ). Moreover, in the profile illustrated in  FIG. 15 , the difference between distance  36  and distance  37  is equal to the distance corresponding to the difference in the delay amounts in delay sections  102 - 2  and  102 - 3 , and the difference between distance  37  and distance  38  is equal to the distance corresponding to the difference in the delay amounts in delay sections  102 - 1  and  102 - 2 . 
     Therefore, since the distance differences between three peaks illustrated in  FIG. 15  are equal to the distances corresponding to the differences in the delay amounts set in respective delay sections  102 - 1  to  102 - 3 , detection processing section  301  judges that an intruding object exists in the intruding object detection region. 
     Moreover, since the distance differences in three peaks illustrated in  FIG. 15  are equal to the distances corresponding to the differences in the delay amounts set in respective delay sections  102 , object positioning section  302  estimates that an intruding object (object  91 ) exists in the direction of a region where the receiving regions of receiving antennas  110 - 1  to  110 - 3  overlaps. Furthermore, object positioning section  302  estimates the distance to an intruding object (object  91 ) using distance  36 ,  37 , or  38  and the delay amounts set in respective delay sections  102 . 
       FIG. 16  illustrates an example of a radar profile when only object  92  exists in  FIG. 12 . 
     As illustrated in  FIG. 12 , object  92  is located in a region not overlapping with the receiving region of receiving antenna  110 - 2  in the receiving region of receiving antenna  110 - 3 . As a result, the reflected wave from object  92  is received only in reflected wave input section  101 - 3  through receiving antenna  110 - 3 . Therefore, only one peak appears in the radar profile illustrated in  FIG. 16 . Therefore, detection processing section  301  judges that any intruding object does not exist in the intruding object detection region. Moreover, since object  92  corresponding to one peak illustrated in  FIG. 16  is located outside the intruding object detection region, object positioning section  302  judges object positioning information not to be generated. 
     Accordingly, in addition to detecting an object intruding in the intruding object detection region, intruding object detection apparatus  300  can specify the position of the object by estimating the direction and distance of the object. 
     Moreover, intruding object detection apparatus  300  receives a reflected wave from an object for intrusion detection in at least two receiving antennas  110  like Embodiment 1, and can thereby detect intrusion of the object into the intruding object detection region without switching of receiving antennas  110 . Consequently, an intruding object can be detected without the need for switching of antennas. Moreover, in the present embodiment, since a processing section for switching antennas is unnecessary like Embodiment 1, an increase in cost of intruding object detection apparatus  100  can be avoid. 
     Moreover, in the present embodiment, even when multiple objects exist in the intruding object detection region simultaneously and multiple peaks exist in the radar profile, intruding object detection apparatus  300  may compare the distance differences between the peaks with the differences in the delay amounts set in respective delay sections  102  and may specify the combination of the matching peaks. That is, intruding object detection apparatus  300  specifies that the peaks of the specified combination represent a reflected wave from the same object. Accordingly, intruding object detection apparatus  300  distinguishes each of multiple objects in the intruding object detection region, and can thereby estimate the direction and distance of each object. 
     Moreover, the present embodiment has been explained in a case where intruding object detection apparatus  300  judges whether the peaks represent reflected waves from the same object on the basis of whether the distances of respective peaks are equal to the delay amounts. However, in order to judge whether multiple peaks appearing in the radar profile represent reflected waves from the same object, intruding object detection apparatus  300  may compare the degrees of similarity of reflective intensity of the respective peaks or the degrees of similarity of phases of the respective peaks and may thereby judge whether the peaks represent reflected waves from the same object. 
     Each embodiment of the present invention has been described thus far. 
     The embodiments of the present invention described above are provided as hardware. The present invention can be achieved through software in concert with hardware. 
     The functional blocks described in the embodiments are achieved by an LSI, which is typically an integrated circuit. The functional blocks may be provided as individual chips, or part or all of the functional blocks may be provided as a single chip. Depending on the level of integration, the LSI may be referred to as an IC, a system LSI, a super LSI, or an ultra LSI. 
     In addition, the circuit integration is not limited to LSI and may be achieved by dedicated circuitry or a general-purpose processor other than an LSI. After fabrication of LSI, a field programmable gate array (FPGA), which is programmable, or a reconfigurable processor which allows reconfiguration of connections and settings of circuit cells in LSI may be used. 
     Should a circuit integration technology replacing LSI appear as a result of advancements in semiconductor technology or other technologies derived from the technology, the functional blocks could be integrated using such a technology. Another possibility is the application of biotechnology and/or the like. 
     An intruding object detection apparatus according to this disclosure is an apparatus that detects intrusion of an object into a region for detection, the apparatus including: an input section that receives signals reflected by a same object existing in the region for detection, using at least two respective antennas among a plurality of antennas; a delay section that delays the signals received respectively using the plurality of antennas using delay amounts that are different from each other, a combining section that combines the delayed signals; a frequency conversion section that frequency-converts the resultant combined signal into a baseband; a detection section that detects the frequency-converted signal; a generation section that generates a profile including distances from the antennas and signal intensity for each of the distances from the antennas using the detected signal; and a detection process section that detects a peak having the signal intensity exceeding a predetermined threshold in the profile and judges whether an intruding object exists in the region for detection based on the detected peak. 
     In addition, in the intruding object detection apparatus according to this disclosure: receiving regions of the at least two antennas do not overlap with each other, and an interval between respective intersection points of respective directivity directions of the at least two antennas and a boundary line of the region for detection is equal to or less than half of a width of a reflective surface of the object for detection; the delay amounts that are different from each other are set so as to equalize path lengths between the intersection points on the boundary line respectively corresponding to the at least two antennas and the combining section; the threshold is set to a larger value than signal intensity capable of being taken by a signal received in any one of the at least two antennas; and when detecting the peak having the signal intensity exceeding the threshold in the profile, the detection process section judges that an intruding object exists in the region for detection. 
     In the intruding object detection apparatus according to this disclosure, when detecting the peak having the signal intensity exceeding the threshold in the profile, and when a distance in the profile corresponding to the detected peak corresponds to a vicinity of the boundary line, the detection process section judges that an intruding object exists in the region for detection. 
     In the intruding object detection apparatus according to this disclosure: at least parts of receiving regions of the at least two antennas overlap with each other; the region for detection is set in a region where the receiving region of the at least two antennas overlap with each other, the threshold is set to a smaller value than signal intensity capable of being taken by a signal received in any one of the at least two antennas; and when at least two peaks having the signal intensity exceeding the threshold are detected in the profile, and when the distance difference between the at least two detected peaks is equal to a distance corresponding to a difference in delay amounts for signals received with the at least two antennas, the detection process section judges that an intruding object exists in the region for detection. 
     The intruding object detection apparatus according to this disclosure further includes a positioning section that, when the detection process section judges that an intruding object exists in the region for detection, estimates a direction of a region where the receiving regions of the at least two antennas overlap with each other, as a direction where the object exists, and estimates distances from the antennas to the object by assuming that the distances from the antennas to the object are as distances obtained by deducting distances corresponding to delay amounts for signals received with the at least two antennas from distances in the profile corresponding to the at least two peaks. 
     An intruding object detection method according to this disclosure is a method for detecting intrusion an object into a region for detection, the method including: receiving signals reflected by a same object existing in the region for detection, using at least two respective antennas among a plurality of antennas; delaying the signals received using the plurality of antennas using delay amounts that are different from each other; combining the respective delayed signals; frequency-converting the resultant combined signal into a baseband; detecting the frequency-converted signal; generating a profile including distances from the antennas and signal intensity for each of the distances from the antennas using the detected signal; and detecting a peak having the signal intensity exceeding a predetermined threshold in the profile, and judging whether an intruding object exists in the region for detection based on the detected peak. 
     The disclosure of Japanese Patent Application No. 2012-043043, filed on Feb. 29, 2012, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
     INDUSTRIAL APPLICABILITY 
     An intruding object detection apparatus and an intruding object detection method according to the present invention is suitable for use in detecting an intruding object without switching of antennas. 
     REFERENCE SIGNS LIST 
     
         
           10  Intruding object detection system 
           100 ,  300  Intruding object detection apparatuses 
           110  Receiving antenna 
           200  Transmission signal generation section 
           210  Transmitting antenna 
           101  Reflected wave input section 
           102  Delay section 
           103  Signal combining section 
           104  Radar profile generation section 
           105 ,  301  Detection processing sections 
           106  Frequency conversion section 
           107  Detection section 
           302  Object positioning section