JP2015087120A - Radio wave sensor and detection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio wave sensor capable of accurately discriminating a type of a detection object in simple and cost-reduced configuration, and a detection method.SOLUTION: The radio wave sensor includes: an antenna part; a transmission part for transmitting a radio wave to an object area via the antenna part; a reception part for receiving a radio wave from the object area via the antenna part; and a discrimination part which executes discrimination processing for discriminating a type of a detection object in the object area on the basis of the radio wave received by the reception part. The antenna part includes an antenna designed to substantially fix reception power of a reflection wave resulting from reflecting the radio wave transmitted by the transmission part in the detection object, regardless of a position of the detection object in the object area.

Description

  The present invention relates to a radio wave sensor and a detection method, and more particularly to a radio wave sensor and a detection method for discriminating the type of detection target using radio waves.

  Japanese Patent Laying-Open No. 2012-247215 (Patent Document 1) discloses an object identification device that is mounted on a vehicle and identifies the type of an object that exists around the vehicle. The object identification device is an object including information on a reflection intensity and a distance to an object around the vehicle obtained by irradiating the vehicle with a sound wave or an electromagnetic wave and detecting the sound wave or a reflected wave of the electromagnetic wave. Information and information on the height of the object obtained by image processing are acquired. The object identification device corrects the reflection intensity according to the height of the object and the distance to the object. Then, the object identification device identifies the type of the object according to the corrected reflection intensity.

SHF Television Broadcasting Promotion Committee, “Measures for future reception problems”, Kenrokukan Publishing Co., Ltd., October 1, 1991, p. 66 Koji Yoichi, 2 others, “Application of expanding millimeter-wave technology”, [online], [October 11, 2013 search], Internet <URL: http: // www. spc. co. jp / spc / pdf / giho21_09. pdf> Takayuki Inaba, Tetsuro Kirimoto, “Automotive Millimeter Wave Radar”, Automotive Technology, February 2010, Vol. 64, No. 2, p. 74-79

JP 2012-247215 A

  However, in the object identification device described in Patent Document 1, the type of the object is identified using the irradiation processing and detection processing of sound waves or electromagnetic waves and image processing, so that the configuration of the device is complicated and expensive. There's a problem.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a radio wave sensor and a detection method capable of accurately determining the type of detection target with a simple and low-cost configuration. That is.

  (1) In order to solve the above-described problem, a radio wave sensor according to an aspect of the present invention includes an antenna unit, a transmission unit that transmits a radio wave to a target area via the antenna unit, and the antenna unit via the antenna unit. A receiving unit that receives a radio wave from the target area; and a determination unit that performs a determination process for determining the type of a detection target in the target area based on the radio wave received by the receiving unit; The antenna includes an antenna designed so that the reception power of the reflected wave reflected by the detection target by the radio wave transmitted by the transmission unit is substantially constant regardless of the position of the detection target in the target area.

  (5) In order to solve the above-described problem, a detection method according to an aspect of the present invention is a detection method in a radio wave sensor including an antenna unit, and transmits a radio wave to a target area via the antenna unit; Receiving a radio wave from the target area via the antenna unit, and performing a determination process for determining a type of a detection target in the target area based on the received radio wave, An antenna designed so that the reception power at the radio wave sensor of the reflected wave reflected from the detection target by the radio wave transmitted through the antenna unit is substantially constant regardless of the position of the detection target in the target area. including.

  The present invention can be realized not only as a radio wave sensor having such a characteristic processing unit, but also as a program for causing a computer to execute such characteristic processing steps. Further, it can be realized as a semiconductor integrated circuit that realizes part or all of the radio wave sensor, or as a system including the radio wave sensor.

  According to the present invention, it is possible to accurately determine the type of detection target with a simple and low-cost configuration.

FIG. 1 is a diagram showing a configuration of a signal control system according to an embodiment of the present invention. FIG. 2 is a diagram showing the configuration of the radio wave sensor in the signal control system according to the embodiment of the present invention. FIG. 3 is a diagram for explaining the directivity of electric power of radio waves transmitted and received by the radio wave sensor according to the embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a transmission antenna and a reception antenna according to the embodiment of the present invention. FIG. 5 is a diagram illustrating an example of the arrangement of the transmission antenna, the reception antenna, and the detection target according to the embodiment of the present invention. FIG. 6 is a diagram showing a configuration of a received power acquisition unit in the radio wave sensor according to the embodiment of the present invention. FIG. 7 is a flowchart defining an operation procedure when the radio wave sensor according to the embodiment of the present invention determines the type of detection target in the target area.

  First, the contents of the embodiment of the present invention will be listed and described.

  (1) A radio wave sensor according to an embodiment of the present invention includes an antenna unit, a transmission unit that transmits radio waves to the target area via the antenna unit, and receives radio waves from the target area via the antenna unit. And a determination unit that performs a determination process for determining the type of detection target in the target area based on the radio wave received by the reception unit, and the antenna unit is transmitted by the transmission unit The antenna includes an antenna designed so that the reception power of the reflected wave reflected by the detection target is substantially constant regardless of the position of the detection target in the target area.

  With such a configuration, the reception power of radio waves from the same type of detection target can be made substantially constant regardless of the position in the detection target area.

  Thereby, regardless of the position of the detection target, the type of the detection target can be accurately determined based on the received power having a magnitude corresponding to the type of the detection target. In addition, since the type of the detection target can be determined without performing image processing, the radio wave sensor can be configured at a low cost and with a simple configuration.

  (2) Preferably, the said discrimination | determination part performs the said discrimination | determination process based on the electric power of the electromagnetic wave received by the said receiving part.

  In this way, with the configuration using the received power that changes according to the type of detection target, for example, the discrimination process can be performed using a simple algorithm that determines the magnitude relationship between one threshold value and the received power. , Processing can be simplified.

  (3) Preferably, the said discrimination | determination part discriminate | determines the person and vehicle in the said target area as said discrimination | determination process.

  With such a configuration, it is possible to accurately discriminate between a vehicle having a large reflection cross-sectional area and a human having a small reflection cross-sectional area based on received power that changes in accordance with the size of the reflection cross-sectional area.

  (4) Preferably, the length of the target area in the directivity direction of the antenna is larger than the length of the target area in a direction orthogonal to the directivity direction.

  As described above, the area of the target area can be maximized by the configuration in which the area corresponding to the characteristics of the antenna is the target area.

  (5) A detection method according to an embodiment of the present invention is a detection method in a radio wave sensor including an antenna unit, and includes a step of transmitting radio waves to a target area via the antenna unit, and via the antenna unit. A step of receiving radio waves from the target area; and a step of performing discrimination processing for discriminating the type of detection target in the target area based on the received radio waves, wherein the antenna unit is connected via the antenna unit. It includes an antenna designed so that the received power of the reflected wave reflected from the detection target by the transmitted radio wave is substantially constant regardless of the position of the detection target in the target area.

  With such a configuration, the reception power of radio waves from the same type of detection target can be made substantially constant regardless of the position in the detection target area.

  Thereby, regardless of the position of the detection target, the type of the detection target can be accurately determined based on the received power corresponding to the type of the detection target. In addition, since the type of the detection target can be determined without performing image processing, the radio wave sensor can be configured at a low cost and with a simple configuration.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated. Moreover, you may combine arbitrarily at least one part of embodiment described below.

[Configuration and basic operation]
FIG. 1 is a diagram showing a configuration of a signal control system according to an embodiment of the present invention.

  With reference to FIG. 1, the signal control system 201 includes a radio wave sensor 101, a signal control device 151, and a pedestrian signal lamp 161. The signal control device 151 and the pedestrian signal lamp 161 in the signal control system 201 constitute a traffic signal device, for example, installed in the vicinity of the intersection CS1.

  The radio wave sensor 101 functions as a moving body detection sensor that detects a detection target Tgt that moves in the target area A1. The radio wave sensor 101 is installed, for example, in the vicinity of the road Rd1 extending to the intersection CS1. Specifically, the radio wave sensor 101 is fixed at a position of height H from the ground, for example, on a support P1 installed near the road Rd1.

  The pedestrian signal lamp 161 and the signal control device 151 are fixed to, for example, the support P1. The radio wave sensor 101 and the signal control device 151 are connected by a signal line (not shown), for example. The signal control device 151 and the pedestrian signal lamp 161 are connected by a signal line (not shown), for example. The radio wave sensor 101 may be installed on the road Rd1 or may be mounted on a car.

  The radio wave sensor 101 determines the type of the detection target Tgt in the target area A1. More specifically, the radio wave sensor 101 transmits a radio wave to the target area A1 including the pedestrian crossing PC1 under the control of the signal control device 151, for example. Specifically, the detection target Tgt is an automobile Tgt1, a pedestrian Tgt2, or the like. The detection target Tgt moves, for example, in the target area A1, and reflects the radio wave transmitted from the radio wave sensor 101.

  The radio wave sensor 101 determines the type of the detection target Tgt based on, for example, the radio wave reflected by the detection target Tgt. More specifically, the radio wave sensor 101 determines a vehicle and a human as the type of the detection target Tgt, for example. The radio wave sensor 101 transmits the determination result to the signal control device 151.

  Under the control of the signal control device 151, the pedestrian signal lamp 161 lights “recommend” or “tore rare”, and displays it for a pedestrian Tgt2 crossing the pedestrian crossing PC1, for example.

  When the signal control device 151 receives the determination result from the radio wave sensor 101, the signal control device 151 controls the pedestrian signal lamp 161 based on the received determination result.

  For example, the signal control device 151 performs a process according to the type of the detection target Tgt when the remaining time for lighting “recommend” in the pedestrian signal lamp 161 is short. Specifically, for example, when the determination result received from the radio wave sensor 101 indicates that the type of the detection target Tgt is human, the signal control device 151 extends the remaining time. Note that the signal control device 151 may notify the pedestrian Tgt2 by voice that, for example, there is little remaining time to light “Recommend”. For example, when the determination result indicates that the type of the detection target Tgt is a vehicle, the signal control device 151 does not extend the remaining time.

  In addition, the signal control device 151 indicates that it is dangerous when the determination result indicates that the type of the detection target Tgt is human, for example, when “Tare rare” is turned on in the pedestrian signal lamp 161. A warning is given to the pedestrian Tgt2 by voice.

  Note that the signal control device 151 may provide a service to the automobile Tgt1 based on the determination result received from the radio wave sensor 101. Specifically, when the determination result indicates that the type of the detection target Tgt is human, for example, the signal control device 151 gives a warning to the car Tgt1 that attention should be paid to the pedestrian Tgt2 in the pedestrian crossing PC1.

[Task]
In order to determine the type of the detection target Tgt located in the target area A1, for example, an intensity sensor for determining the type of the detection target Tgt located in the target area A1 using the intensity of the reflected wave of the irradiated radio wave Can be considered. For example, in the state where the intensity sensor is fixed to the column P1, when the automobile Tgt1 is located at a location farther from the intensity sensor than the pedestrian Tgt2 as in the case of the radio wave sensor 101 shown in FIG. The strength of is as follows.

  That is, the difference between the intensity of the reflected wave from the automobile Tgt1 having a large reflection sectional area and the intensity of the reflected wave from the pedestrian Tgt1 having a small reflection sectional area is reduced. Here, the reflection cross-sectional area is a value determined by the reflectance and area of the surface portion where the detection target Tgt reflects the radio wave irradiated from the intensity sensor. For example, the reflection cross-section of the automobile Tgt1 is the pedestrian Tgt2 It is about 10 dB larger than the reflection cross section. In this case, it is difficult for the intensity sensor to determine the type of the detection target Tgt based on the intensity of the reflected wave from the detection target Tgt.

  Further, for example, it is conceivable to provide a function for detecting position information of the detection target Tgt to the intensity sensor. The position information of the detection target Tgt is calculated based on, for example, the distance and direction. At this time, the following problems occur in the intensity sensor.

  That is, since it is necessary to perform discrimination processing based on the intensity of the reflected wave according to the position information, signal processing becomes complicated. A plurality of receiving systems for measuring the azimuth of the detection target Tgt are required, which is expensive. In general, since the measurement error is large for the azimuth, there is a high possibility that the determination is erroneous due to the detection error of the position information resulting from the measurement error.

  Further, for example, a radar that irradiates a radio wave with a beam width narrowed to about 0.1 ° every 0.1 °, and scans the position, size, and shape of the detection target Tgt based on the reflected wave of the irradiated radio wave. Can be considered. However, since such radar is expensive, it is difficult to install it at many intersections.

  Further, for example, it is conceivable to use a Doppler sensor capable of measuring the detection target speed. The detection target speed is a moving speed of the target object along a direction in which the target object approaches or moves away from the Doppler sensor. The Doppler sensor can determine the type of the detection target Tgt when the detection target speed of the automobile Tgt1 and the detection target speed of the pedestrian Tgt2 are greatly different.

  On the other hand, for example, when the car Tgt1 crosses the pedestrian crossing PC1 while turning right at the intersection CS1 at the speed vc in the state in which the Doppler sensor is fixed to the column P1, as in the case of the radio wave sensor 101 shown in FIG. The detection target speed vcd for the Doppler sensor is a component of the speed vc in the axial direction connecting the Doppler sensor and the automobile Tgt1. The detection target speed vmd for the Doppler sensor of the pedestrian Tgt2 crossing the pedestrian crossing PC1 at the speed vm is substantially the same as the speed vm. Therefore, in the case shown in FIG. 1, the difference between the detection target speed vmd and the detection target speed vcd becomes small. Therefore, the Doppler sensor determines the type of the detection target Tgt based on the detection target speed of the detection target Tgt. It becomes difficult.

  Therefore, the radio wave sensor according to the embodiment of the present invention solves such a problem by the following configuration and operation.

[Configuration of radio wave sensor]
FIG. 2 is a diagram showing the configuration of the radio wave sensor in the signal control system according to the embodiment of the present invention.

  Referring to FIG. 2, radio wave sensor 101 includes transmission unit 1, reception unit 2, antenna unit 3, A / D converter (ADC) 23, received power acquisition unit 24, and determination unit 25. . The transmission unit 1 includes a millimeter wave generation unit 11, a power amplifier 15, and a directional coupler 16. The millimeter wave generator 11 includes a voltage generator 12 and a voltage controlled oscillator 13. The receiving unit 2 includes a low noise amplifier 18, a mixer 20, an IF (Intermediate Frequency) amplifier 21, and a low-pass filter 22. The antenna unit 3 includes a transmission antenna 14 and a reception antenna 17.

  More specifically, in the antenna unit 3, the reception power of its own radio wave sensor 101 of the reflected wave reflected from the detection target Tgt by the radio wave transmitted by the transmission unit 1 depends on the position of the detection target Tgt in the target area A1. It includes a transmission antenna 14 and a reception antenna 17 that are designed to be substantially constant. Here, “substantially constant” means that the received power of the reflected wave at its own radio wave sensor 101 may be regarded as constant regardless of the position of the detection target Tgt in the target area A1.

  Preferably, the antenna unit 3 is a transmitting antenna designed so that the received power of the reflected wave in the radio wave sensor 101 is constant with an error of ± 4 dB regardless of the position of the detection target Tgt in the target area A1. 14 and a receiving antenna 17.

  More preferably, the antenna unit 3 is designed so that the reception power of the reflected wave in the own radio wave sensor 101 is constant with an error of ± 3 dB regardless of the position of the detection target Tgt in the target area A1. An antenna 14 and a receiving antenna 17 are included.

  The transmission unit 1 transmits radio waves to the target area A1 via the antenna unit 3. Specifically, the millimeter wave generation unit 11 in the transmission unit 1 generates a radio wave having a frequency of, for example, 76 GHz, that is, a millimeter wave, and outputs the generated millimeter wave to the directional coupler 16. Note that the millimeter wave generator 11 may generate a radio wave having a frequency of, for example, 24 GHz band, 60 GHz band, or 79 GHz band.

  More specifically, the voltage generation unit 12 in the millimeter wave generation unit 11 generates, for example, a constant voltage and outputs the generated constant voltage to the voltage controlled oscillator 13. Specifically, the voltage controlled oscillator 13 is a VCO (Voltage-controlled oscillator), generates a transmission wave that is a millimeter wave having a frequency according to a constant voltage received from the voltage generation unit 12, and directs the generated transmission wave to a direction. To the sex coupler 16.

  The directional coupler 16 distributes the transmission wave received from the millimeter wave generator 11 to the power amplifier 15 and the receiver 2. The power amplifier 15 amplifies the transmission wave received from the directional coupler 16 and outputs it to the transmission antenna 14 in the antenna unit 3.

  FIG. 3 is a diagram for explaining the directivity of electric power of radio waves transmitted and received by the radio wave sensor according to the embodiment of the present invention.

  Referring to FIG. 3, transmission antenna 14 is fixed at a position of height H from the ground, for example. As shown in FIG. 1, the transmission antenna 14 is installed, for example, such that the direction Dir of the transmission wave is a direction that intersects the traveling direction of the detection target Tgt in the target area A1. Here, the direction Dir is, for example, a direction from the transmission antenna 14 to the center Ctr of the target area A1.

  A point A shown in FIG. 3 is located in the target area A1 and on the x-axis including the point Zd on the ground vertically below the transmission antenna 14 and the center Ctr of the target area A1. The distance from the transmitting antenna 14 to the point A is defined as LA. A depression angle from the transmitting antenna 14 to the point A with respect to the horizontal line is defined as θA. At two intersections between the x-axis and the target area A1, points A1n and A1f are defined in order from the side closer to the transmission antenna 14. Also, the depression angles from the transmitting antenna 14 to the points A1n and A1f are defined as θAn and θAf, respectively.

  The transmission antenna 14 transmits the transmission wave received from the power amplifier 15 to the target area A1. The transmission antenna 14 is designed so that, for example, the reception power of radio waves from itself in a range on the x-axis corresponding to the predetermined range is substantially constant at a radio wave transmission angle or depression angle within a predetermined range.

  Specifically, the transmission antenna 14 is configured so that, for example, the reception power of the radio wave from itself in the range from the point A1n to the point A1f on the x axis is substantially constant at the radio wave transmission angle from θAn to θAf. Designed.

Hereinafter, the radiation electric field intensity from the transmitting antenna 14 to the point A will be considered. That is, assuming that the antenna radiation field strength at point A in the transmission antenna 14 is E0 (θA), when the distance LA is sufficiently longer than the wavelength of the transmission wave, the field strength EA at point A is expressed by the following equation (1). The

The distance LA is expressed by the following formula (2).

By substituting LA in equation (2) into equation (1), the electric field strength EA is expressed by the following equation (3).

When the point A is located in the range from the point A1n to the point A1f on the x-axis, the condition for the electric field intensity at the point A to be constant regardless of the depression angle θA is that θA is in the range from θAn to θAf. , E0 (θA) should satisfy the following expression (4).

  Here, ktf is an arbitrary constant. That is, the antenna radiation electric field intensity E0 (θA) is designed to be proportional to the remainder of the depression angle θA, that is, the cosecant.

Further, the received power PA at the point A is expressed by the following equation (5) based on the equation (3).

Here, Y is a value determined by, for example, the impedance of the space. In equation (5), the antenna radiation electric field strength E0 (θA) is obtained by using the product of the transmission power P0 of the millimeter wave transmitted by the transmission antenna 14 and the transmission gain GT (θA) in the direction toward the point A of the transmission antenna 14. The received power PA is expressed by the following equation (6).

  That is, designing the antenna radiation electric field intensity E0 (θA) to be proportional to the cosecant of the depression angle θA corresponds to designing the transmission gain GT (θA) to be proportional to the square of the cosecant of the depression angle θA.

  Further, the length A1d of the target area in the directivity direction Dir of the transmission antenna 14 is larger than the length of the target area in the direction orthogonal to the direction of the directivity Dir. Thereby, the electric field strength of the transmission wave, that is, the reception power at an arbitrary position in the target area A1 can be made substantially constant.

  FIG. 4 is a diagram illustrating an example of a transmission antenna and a reception antenna according to the embodiment of the present invention.

  Referring to FIG. 4, the transmitting antenna 14 is, for example, the SHF television broadcasting spread promotion study group, “Future reception failure countermeasures”, Kenrokukan Publishing Co., Ltd., October 1, 1991, p. 66 (Non-Patent Document 1), which is a cosecant beam antenna, including a special mirror reflector 41, a primary radiator 42, and a rectangular waveguide 43.

  The primary radiator 42 in the transmission antenna 14 radiates the transmission wave received from the power amplifier 15 via the rectangular waveguide 43 to the special specular reflection mirror 41. The special specular reflecting mirror 41 reflects the transmission wave radiated from the primary radiator 42 and transmits the transmission wave to the target area A1 so that the transmission gain GT (θA) is proportional to the square of the cosecant of the depression angle θA.

  Referring to FIG. 2 again, receiving antenna 17 is, for example, a cosecant beam antenna similar to transmitting antenna 14 shown in FIG. The receiving antenna 17 is installed, for example, in the vicinity of the transmitting antenna 14 so that the directivity direction is substantially parallel to the directivity direction Dir of the transmitting antenna 14.

  The receiving antenna 17 receives radio waves from the target area A1. More specifically, the primary radiator in the receiving antenna 17 receives a millimeter wave, that is, a reflected wave from the target area A1 reflected by the special specular reflector, and receives the received reflected wave via a rectangular waveguide. Output to 2.

  The reflected wave received by the receiving antenna 17 includes, for example, a detection target reflected wave generated when the surface of the detection target Tgt moving in the target area A1 reflects the transmission wave transmitted by the transmission antenna 14.

  The power Ptr of the detection target reflected wave is proportional to the reception power of the transmission wave on the surface of the detection target Tgt and the reflection cross-sectional area σ of the detection target Tgt. Further, as described above, the reception power of the transmission wave received by the detection target Tgt in the target area A1 is substantially constant. Therefore, the detection target Tgt having the same reflection cross-sectional area σ generates a detection target reflected wave having a substantially constant power Ptr at any position in the target area A1.

  Referring to FIG. 3 again, the receiving antenna 17 is designed so that, for example, the power of the received radio wave is substantially constant at a predetermined range of radio wave reception angles, that is, depression angles. Specifically, the receiving antenna 17 is, for example, from a detection target Tgt having the same reflection cross-sectional area σ located in a range from a point A1n to a point A1f on the x axis at a reception angle of a radio wave from θAn to θAf. It is designed so that the reception power of the detection target reflected wave is substantially constant.

  More specifically, as in the case of the transmission antenna 14, GR (θA) indicating the depression angle characteristic of the reception gain of the reception antenna 17 is designed to be proportional to the square of the cosecant of the depression angle θA, for example. Similarly to the case of the transmission antenna 14, the length of the target area in the direction of the directivity of the reception antenna 17 is larger than the length of the target area in the direction orthogonal to the direction of the directivity. Thereby, the reception power of the detection target reflected wave received from the target area A1 can be made substantially constant.

  Therefore, the reception power of the detection target reflected wave from the detection target Tgt having the same reflection cross-sectional area σ can be made substantially constant regardless of the position of the detection target Tgt in the target area A1.

  FIG. 5 is a diagram illustrating an example of the arrangement of the transmission antenna, the reception antenna, and the detection target according to the embodiment of the present invention.

  With reference to FIG. 5, the speed of the detection target Tgt relative to the receiving antenna 17 is defined as a relative speed vt. Further, among the components of the relative speed vt, a component along a direction approaching or moving away from the radio wave sensor 101 is defined as a detection target speed vd. In other words, the detection target speed vd corresponds to the inner product of the unit vector nd in the direction from the detection target Tgt to the reception antenna 17 and the relative speed vt.

  Note that the radio wave sensor 101 may be fixed to, for example, a support that does not move with respect to the ground, such as the column P1, or may be fixed to a thing that moves with respect to the ground. For example, when the radio wave sensor 101 is fixed to the support P1, the receiving antenna 17 and the target area A1 are fixed with respect to the ground, so the relative speed vt is also the relative speed of the detection target Tgt with respect to the ground.

  The frequency f1r of the detection target reflected wave received by the reception antenna 17 is shifted according to the detection target speed vd of the detection target Tgt with respect to the frequency f1 of the transmission wave.

More specifically, when the transmission wave T1 (t) is expressed by the following equation (7), the detection target reflected wave R1d (t) is Koji Yoichi, two others, “Application of Expanding Millimeter Wave Technology”. [Online], [October 11, 2013 search], Internet <URL: http: // www. spc. co. jp / spc / pdf / giho21_09. pdf> (Non-Patent Document 2) and Takayuki Inaba, Tetsuro Kirimoto, “Vehicle Millimeter Wave Radar”, Automotive Technology, February 2010, Vol. 64, No. 2, p. As shown in 74-79 (Non-Patent Document 3), it is represented by the following formula (8).

  Here, β1 is an initial phase. A is the amplitude of the transmitted wave. LA is a distance between the receiving antenna 17 and the detection target Tgt. c is the speed of light. a is a value determined by, for example, the amplitude A, the wavelength of the transmission wave, the reflection cross-sectional area σ, and the like.

  The frequency f1r of the detection target reflected wave R1d (t) is a frequency obtained by adding f1 × (2 × vd / c) to the frequency f1 of the transmission wave T1 (t) as shown in Expression (8). . Specifically, when the detection target Tgt moves in a direction approaching the reception antenna 17, vd becomes positive, so the frequency f1r is higher than the frequency f1, and the detection target Tgt moves in a direction away from the reception antenna 17. When vd becomes negative, the frequency f1r is lower than the frequency f1.

The reflected wave R1 (t) received by the receiving antenna 17 generally includes a detection target reflected wave R1d (t) and a non-detected target reflected wave R1nd (t) from a portion other than the detection target Tgt. Therefore, the reflected wave R1 (t) is a superposition of the detection target reflected wave R1d (t) and the non-detection target reflected wave R1nd (t), and is expressed by the following equation (9).

  Here, a situation is assumed in which the detection target speed other than the detection target Tgt is zero, that is, a situation where the frequency of the non-detection target reflected wave R1nd (t) is the same as the frequency f1 of the transmission wave T1 (t).

  Referring to FIG. 2 again, the receiving unit 2 receives the reflected wave R1 (t) from the target area A1 via the receiving antenna 17 in the antenna unit 3. And the receiving part 2 detects the received reflected wave R1 (t), for example. More specifically, the low noise amplifier 18 in the receiving unit 2 amplifies the reflected wave R1 (t) received by the receiving antenna 17 and outputs the amplified wave to the mixer 20.

  The mixer 20 multiplies the transmission wave T1 (t) and the reflected wave R1 (t), and has a difference having a frequency component that is the difference between the frequency component of the transmission wave T1 (t) and the frequency component of the reflected wave R1 (t). A sum frequency signal having a frequency component that is the sum of the signal and both frequency components is generated.

In the mixer 20, the differential signal B1 (t) generated from the transmission wave T1 (t) and the reflected wave R1 (t) is expressed by the following equation (10), for example.

  Here, B1d (t) is a difference signal generated from the transmission wave T1 (t) and the detection target reflected wave R1d (t). K is the amplitude of the difference signal B1d (t). −4π × f1 × LA / c is the delay phase γ1. 2 × f1 × vd / c is the Doppler frequency f1d. DC1 is a differential signal generated from the transmission wave T1 (t) and the non-detection target reflected wave R1nd (t), and the frequency of the non-detection target reflection wave R1nd (t) is that of the transmission wave T1 (t). Since it is the same as the frequency f1, it becomes a DC component.

  The IF amplifier 21 is an amplifier having a large amplification factor from, for example, a low frequency band to an intermediate frequency band, and greatly amplifies the difference signal B1 (t) among the difference signal B1 (t) and the sum frequency signal generated in the mixer 20. Amplified at a rate, and outputs the amplified differential signal B 1 (t) to the low-pass filter 22.

  The low-pass filter 22 attenuates a component having a predetermined frequency or higher, for example, a component having a frequency of 1 kHz or higher, among the frequency components of the differential signal B1 (t) amplified by the IF amplifier 21.

  The A / D converter 23 performs sampling processing of the difference signal B1 (t) using, for example, a predetermined sampling frequency. More specifically, the A / D converter 23 converts the differential signal B1 (t) that has passed through the low-pass filter 22 into a digital signal of m bits (m is a natural number of 2 or more) using a predetermined sampling frequency, for example. The converted digital signal is output to the received power acquisition unit 24.

  FIG. 6 is a diagram showing a configuration of a received power acquisition unit in the radio wave sensor according to the embodiment of the present invention.

  Referring to FIG. 6, received power acquisition unit 24 includes a buffer 51 and a received power calculation unit 52.

  For example, the buffer 51 accumulates a digital signal received from the A / D converter 23 for a predetermined observation time Tobs, specifically, 100 milliseconds.

  For example, when the accumulation of the digital signal is completed in the buffer 51, the reception power calculation unit 52 calculates the reception power of the detection target reflected wave R1d (t) based on the accumulated digital signal Sd.

  More specifically, the digital signal Sd includes, for example, a vibration component having an amplitude proportional to the reflection sectional area σ of the detection target Tgt and a frequency f1d. For example, the received power calculation unit 52 extracts the vibration component from the digital signal Sd, and calculates the amplitude of the extracted vibration component as the received power Pr of the detection target reflected wave R1d (t). The received power calculation unit 52 outputs the calculated received power Pr to the determination unit 25.

  Referring to FIG. 2 again, when receiving the reception power Pr from the reception power calculation unit 52 in the reception power acquisition unit 24, the determination unit 25 determines the type of the detection target Tgt in the target area A1 based on the received reception power Pr. Is a human or a vehicle.

  More specifically, as described above, the reception power Pr of the detection target reflected wave from the detection target Tgt having the same reflection cross-sectional area σ is substantially constant regardless of the position of the detection target Tgt in the target area A1.

  Therefore, the received power Prc based on the detection target reflected wave R1d (t) from the automobile Tgt1 having the reflection cross-sectional area σc is substantially constant regardless of the position of the automobile Tgt1 in the target area A1. Similarly, the received power Prm based on the detection target reflected wave R1d (t) from the pedestrian Tgt2 having the reflection cross-sectional area σm is substantially constant regardless of the position of the pedestrian Tgt2 in the target area A1.

  For example, since the reflection sectional area σc of the automobile Tgt1 is about 10 dB larger than the reflection sectional area σm of the pedestrian Tgt2, the reception power Prc is about 10 dB larger than the reception power Prm.

  For example, based on the magnitude relationship between the predetermined threshold Thp set between the received power Prc and the received power Prm and the received power Pr, the determination unit 25 is a person whose detection target Tgt in the target area A1 is human. It is determined whether it is a vehicle or a vehicle.

  Specifically, the determination unit 25 determines that the type of the detection target Tgt is a vehicle, for example, when the reception power Pr is equal to or greater than the threshold Thp. For example, when the received power Pr is smaller than the threshold Thp, the determination unit 25 determines that the type of the detection target Tgt is human. The determination unit 25 transmits the determination result to the signal control device 151.

  Although the antenna unit 3 according to the embodiment of the present invention is configured to include the transmission antenna 14 and the reception antenna 17, the present invention is not limited to this. The antenna unit 3 may include a common antenna having both a radio wave transmission function and a radio wave reception function.

When a common antenna is used, the received power Pr is expressed by a radar equation shown in the following formula (11), for example.

  Here, Pt is the power of the transmission wave. G is the antenna gain of the common antenna. λ is the wavelength of millimeter waves transmitted and received by the radio wave sensor 101. Similar to the depression characteristics of the transmission gain GT (θA) and the reception gain GR (θA), when the depression characteristics of the antenna gain of the common antenna are designed to be proportional to the square of the cosecant of the depression angle θA, for example, The reception power Pr of the detection target reflected wave from the detection target Tgt having the area σ can be made substantially constant regardless of the position of the detection target Tgt in the target area A1.

  In addition, the antenna unit 3 according to the embodiment of the present invention includes a cosecant beam designed so that the power of the received radio wave is substantially constant at a predetermined range of radio wave transmission angles and a predetermined range of radio wave reception angles. Although the configuration includes an antenna, the configuration is not limited to this. The antenna unit 3 includes a cosecant beam antenna designed so that the power of a received radio wave is substantially constant at at least one of a predetermined range of radio wave transmission angles and a predetermined range of radio wave reception angles. I just need it.

[Operation]
FIG. 7 is a flowchart defining an operation procedure when the radio wave sensor according to the embodiment of the present invention determines the type of detection target in the target area. The radio wave sensor 101 in the signal control system 201 includes a computer, and an arithmetic processing unit such as a CPU in the computer reads and executes a program including a part or all of each step of the following flowchart from a memory (not shown). The program of this apparatus can be installed from the outside. The program of this device is distributed in a state stored in a recording medium.

  Referring to FIG. 7, for example, radio wave sensor 101 sets the observation time Tobs as one observation cycle, and performs a discrimination process based on reflected wave R1 (t) with respect to transmission wave T1 (t) transmitted during one observation cycle. Do.

  First, for example, when the radio wave sensor 101 receives a measurement start command from the signal control device 151, the radio wave sensor 101 sets a count value Ct for counting the observation cycle to zero and targets the transmission wave T1 (t) from the transmission antenna 14. It transmits to area A1 (step S102).

  Next, the radio wave sensor 101 increments the count value Ct and starts the Ct + 1th observation cycle (step S104).

  Next, the radio wave sensor 101 outputs a digital signal Sd obtained by A / D converting the differential signal B1 (t) generated from the reflected wave R1 (t) and the transmission wave T1 (t) during the Ct + 1th observation cycle. Accumulate in the buffer 51 (step S106).

  Next, when the accumulated digital signal Sd includes a digital signal Sd that is larger than the predetermined value Tha (YES in step S108), the radio wave sensor 101 calculates the received power Pr as an evaluation value based on the digital signal Sd (step S108). S110).

  Next, the radio wave sensor 101 checks whether Ct is 10 or more (step S112).

  On the other hand, when there is no digital signal Sd larger than the predetermined value Tha in the accumulated digital signal Sd (NO in step S108), the radio wave sensor 101 checks whether Ct is 10 or more (step S112).

  Next, when Ct is 10 or more (YES in step S112), radio wave sensor 101 calculates an evaluation value in five or more observation cycles among the latest 10 observation cycles (YES in step S114). The average value Ave of the evaluation values calculated in the 10 observation cycles is calculated (step S116).

  On the other hand, the radio wave sensor 101 counts when Ct is not 10 or more (NO in step S112) or when an evaluation value is not calculated in 5 or more observation cycles among the latest 10 observation cycles (NO in step S114). The value Ct is incremented, and the Ct + 1th observation cycle is started (step S104).

  Next, when the calculated average value Ave is smaller than the threshold value Thp (YES in step S118), the radio wave sensor 101 determines that the type of the detection target Tgt in the target area A1 is a human and determines the determination result as a signal control device 151. (Step S122).

  On the other hand, when the calculated average value Ave is equal to or greater than the threshold value Thp (NO in step S118), the radio wave sensor 101 determines that the type of the detection target Tgt in the target area A1 is a vehicle, and the determination result is the signal control device 151. (Step S120).

  Next, the radio wave sensor 101 increments the count value Ct and starts the Ct + 1th observation cycle (step S104).

  For example, the radio wave sensor 101 may create a frequency spectrum of the difference signal B1 (t), and calculate the detection target speed vd based on the peak frequency of the created frequency spectrum and Expression (8). For example, the radio wave sensor 101 may add the calculated detection target speed vd as information for determination processing.

  The radio wave sensor 101 is a detection target of the detection target Tgt in accordance with, for example, the two-frequency CW (Continuous-Wave) method and the FM-CW (Frequency-Modulated CW) method described in Non-Patent Document 1 and Non-Patent Document 2. The speed vd and the distance L to the detection target may be calculated, and the calculated detection target speed vd and the distance L may be added as information for determination processing.

  Specifically, for example, in step S122, the radio wave sensor 101 performs the following process instead of determining that the type of the detection target Tgt in the target area A1 is human.

  That is, for example, when the detection target speed vd is larger than a predetermined threshold value Thv, specifically, 30 kilometers per hour, the radio wave sensor 101 suspends the determination process.

  More specifically, when the detection target speed vd is larger than the threshold value Thv, there is a high possibility that the type of the detection target Tgt is a vehicle. Therefore, there is a high possibility that the determination based on the received power Pr is incorrect.

  For example, when the distance L is greater than the predetermined threshold value Thl, the radio wave sensor 101 suspends the determination process.

  More specifically, for example, in the case where the distance between the radio wave sensor 101 and the target area A1 is 30 to 40 meters which is known, when the calculated distance L is 100 meters, there is a high possibility that the measurement is not correctly performed. Therefore, there is a high possibility that the determination based on the received power Pr is incorrect.

  For example, when the detection target speed vd is equal to or less than the predetermined threshold value Thv and the distance L is equal to or less than the predetermined threshold value Thl, the radio wave sensor 101 sets the type of the detection target Tgt in the target area A1 to human. And the determination result is transmitted to the signal control device 151.

  As described above, when there is a high possibility that the determination based on the received power Pr is incorrect, the radio wave sensor 101 transmits an erroneous determination result to the signal control device 151 by holding the determination process. It can be avoided.

  By the way, in the object identification device described in Patent Document 1, the type of the object is identified using the sound wave or electromagnetic wave irradiation processing and detection processing and the image processing, so that the configuration of the device is complicated and costly. There's a problem.

  On the other hand, the radio wave sensor according to the embodiment of the present invention includes the antenna unit 3, the transmission unit 1 that transmits radio waves to the target area A1 via the antenna unit 3, and the target area A1 via the antenna unit 3. Receiving section 2 that receives the radio waves from the receiver 2 and a determination section 25 that performs a determination process for determining the type of the detection target Tgt in the target area A1 based on the radio waves received by the reception section 2. The antenna unit 3 is configured such that the reception power Pr of the detection target reflected wave reflected by the detection target Tgt of the radio wave transmitted by the transmission unit 1 is substantially constant regardless of the position of the detection target Tgt in the target area A1. Designed includes a transmit antenna 14 and a receive antenna 17. In other words, the antenna unit 3 includes the transmission antenna 14 and the reception unit which are designed so that the power of the received radio wave is constant at at least one of the transmission angle of the predetermined range of radio waves and the reception angle of the radio wave of the predetermined range. An antenna 17 is included.

  With such a configuration, the reception power Pr of the radio wave from the detection target Tgt having the same reflection sectional area σ can be made substantially constant regardless of the position of the detection target Tgt in the target area A1.

  Accordingly, the reflection cross-sectional area σ of the detection target Tgt can be recognized from the reception power Pr of the radio wave from the detection target Tgt regardless of the position of the detection target Tgt. The type of the target Tgt can be determined with high accuracy. In addition, since the type of the detection target Tgt can be determined without performing image processing, the radio wave sensor 101 can have a low cost and a simple configuration.

  For example, it is conceivable to provide a function for detecting position information of the detection target Tgt to an intensity sensor for determining the type of the detection target Tgt located in the target area A1 using the intensity of the reflected wave of the irradiated radio wave. It is done. The position information of the detection target Tgt is calculated based on, for example, the distance and direction. At this time, the intensity sensor has the following problems.

  That is, since it is necessary to perform discrimination processing based on the intensity of the reflected wave according to the position information, signal processing becomes complicated. A plurality of receiving systems for measuring the azimuth of the detection target Tgt are required, which is expensive. In general, since the measurement error is large for the azimuth, there is a high possibility that the determination is erroneous due to the detection error of the position information resulting from the measurement error.

  On the other hand, in the radio wave sensor according to the embodiment of the present invention, the discrimination unit 25 performs discrimination processing based on the power of the radio wave received by the reception unit 2.

  In this way, with the configuration using the received power Pr that changes in accordance with the reflection cross-sectional area σ of the detection target Tgt, for example, a discrimination process using a simple algorithm that determines the magnitude relationship between one threshold value and the received power Pr. Therefore, the process can be simplified.

  In addition, for example, the determination process can be performed without using information other than the received power Pr such as the position information of the detection target Tgt, so that the configuration of the receiving system can be simplified, and the determination result is erroneous due to the detection error of the position information. Can be avoided.

  In the radio wave sensor according to the embodiment of the present invention, the determination unit 25 determines a person and a vehicle in the target area A1 as the determination process.

  With such a configuration, it is possible to accurately discriminate between a vehicle having a large reflection sectional area σ and a human having a small reflection sectional area σ based on the received power Pr that changes in accordance with the magnitude of the reflection sectional area σ. it can.

  In the radio wave sensor according to the embodiment of the present invention, the length of the target area A1 in the directionality of at least one of the transmission antenna 14 and the reception antenna 17 is in the direction orthogonal to the directionality of the directivity. It is larger than the length of the target area A1.

  Thus, the area of the target area A1 can be maximized by the configuration in which the area corresponding to the characteristics of at least one of the transmission antenna 14 and the reception antenna 17 is the target area A1.

  In the radio wave sensor according to the embodiment of the present invention, the type of the automobile Tgt1 and the pedestrian Tgt2 is determined as the detection target Tgt. However, the present invention is not limited to this. The radio wave sensor can also be applied to, for example, discriminating the types of detection targets Tgt including two-wheeled vehicles such as bicycles and motorcycles in addition to the automobile Tgt1 and the pedestrian Tgt2.

  In the radio wave sensor according to the embodiment of the present invention, the reception power Pr is obtained based on the difference signal generated from the transmission wave and the reflected wave. However, the present invention is not limited to this. For example, the radio wave sensor may be configured to acquire the reception power Pr based on a difference signal in an intermediate frequency band generated from a local signal having a frequency different from the frequency of the transmission wave and a reflected wave.

  The above embodiment should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  The above description includes the following features.

[Appendix 1]
An antenna section;
A transmission unit that transmits radio waves to the target area via the antenna unit;
A receiving unit for receiving radio waves from the target area via the antenna unit;
A determination unit that performs a determination process for determining a type of a detection target in the target area based on radio waves received by the reception unit;
The antenna unit is an antenna designed so that the reception power of the reflected wave reflected by the detection target by the radio wave transmitted by the transmission unit is substantially constant regardless of the position of the detection target in the target area. Including
Preferably, the antenna unit includes an antenna designed so that the received power becomes constant with an error of ± 4 dB regardless of the position of the detection target in the target area,
More preferably, the antenna unit includes an antenna designed so that the received power becomes constant with an error of ± 3 dB regardless of the position of the detection target in the target area,
The determination unit performs the determination process based on the magnitude relationship between the power of the radio wave received by the reception unit and a predetermined threshold value,
The discrimination unit is a radio wave sensor that discriminates a person and a vehicle in the target area as the discrimination process.

DESCRIPTION OF SYMBOLS 1 Transmission part 2 Reception part 3 Antenna part 11 Millimeter wave generation part 12 Voltage generation part 13 Voltage control oscillator 14 Transmission antenna 15 Power amplifier 16 Directional coupler 17 Reception antenna 18 Low noise amplifier 20 Mixer 21 IF amplifier 22 Low pass filter 23 A / D converter 24 Received power acquisition unit 25 Discrimination unit 41 Special mirror reflector 42 Primary radiator 43 Rectangular waveguide 51 Buffer 52 Received power calculation unit 101 Radio wave sensor 151 Signal controller 161 Pedestrian signal lamp 201 Signal control system

Claims (5)

An antenna section;
A transmission unit that transmits radio waves to the target area via the antenna unit;
A receiving unit for receiving radio waves from the target area via the antenna unit;
A determination unit that performs a determination process for determining a type of a detection target in the target area based on radio waves received by the reception unit;
The antenna unit is an antenna designed so that the reception power of the reflected wave reflected by the detection target by the radio wave transmitted by the transmission unit is substantially constant regardless of the position of the detection target in the target area. Including radio wave sensor.   The radio wave sensor according to claim 1, wherein the discrimination unit performs the discrimination process based on power of radio waves received by the reception unit.   The radio wave sensor according to claim 1, wherein the determination unit determines a person and a vehicle in the target area as the determination process.   The radio wave according to any one of claims 1 to 3, wherein a length of the target area in a directionality of the antenna is larger than a length of the target area in a direction orthogonal to the directionality of the antenna. Sensor. A detection method in a radio wave sensor including an antenna unit,
Transmitting radio waves to the target area via the antenna unit;
Receiving radio waves from the target area via the antenna unit;
Performing a discrimination process for discriminating the type of detection target in the target area based on the received radio wave,
The antenna unit is configured so that the reception power of the reflected wave reflected by the detection target of the radio wave transmitted through the antenna unit is substantially constant regardless of the position of the detection target in the target area. A sensing method including a designed antenna.

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