Moving object detection device

Abstract

To provide a mobile body detector which can easily remove a signal component alone of proximity or separation of a mobile body.SOLUTION: A doppler sensor 2 as a mobile body detector includes: a substrate 20 having a front surface and a back surface; a transmission antenna 3 provided in the front surface of the substrate 20, the transmission antenna sending a radio wave to the mobile body; and a reception antenna 4 provided in the front surface of the substrate 20, the reception antenna receiving a radio wave reflected by the mobile body. The substrate 20 has an opening 21 for passage of the mobile body between the transmission antenna 3 and the reception antenna 4.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a mobile object detection device. [Background technology]

[0002] When a moving object is detected using the CW Doppler method (CWD: continuous wave doppler), which is one of the detection methods used by radio wave radar sensors, it is possible to determine whether the object is approaching or moving away by examining the relationship between the I and Q signals through signal analysis (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-156441 [Patent Document 2] Japanese Patent Application Publication No. 9-127232 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when the moving object is a fluid (water flow, powder passing through a pipe, etc.) or a continuous object (a thread, a plate, etc.), both the approaching and separating parts of the fluid or continuous object passing through the sensor are observed, making it difficult to determine whether they are approaching or separating.In addition, analyzing the IF signals (I signal and Q signal) to check the state of the moving object becomes complicated.

[0005] An object of the present invention is to provide a moving body detection device that can easily extract only a signal component representing either the approach or departure of a moving body. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the mobile object detection device disclosed in the specification comprises a substrate having a front surface and a back surface, a transmitting antenna provided on the front surface of the substrate for transmitting radio waves toward the mobile object, and a receiving antenna provided on the front surface of the substrate for receiving radio waves reflected by the mobile object, wherein the substrate has an opening between the transmitting antenna and the receiving antenna for allowing the mobile object to pass through. [Effects of the Invention]

[0007] According to the present invention, it is possible to easily extract only the signal component of either the approach or departure of a moving object. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a signal processing device having a moving body detection device according to an embodiment of the present invention; [Figure 2] 10A and 10B are diagrams illustrating an example of an I signal and a Q signal output from a Doppler sensor when a moving object passes in front of the Doppler sensor. [Figure 3] FIG. 2 is a diagram illustrating the configuration of a Doppler sensor. [Figure 4] FIG. 2 is a cross-sectional view of a substrate. [Figure 5] FIG. 10 is a configuration diagram of a first modified example of the Doppler sensor. [Figure 6] FIG. 10 is a configuration diagram of a second modified example of the Doppler sensor. [Figure 7] FIG. 10(A) is a configuration diagram of a reference example of a Doppler sensor, and FIG. 10(B) is a configuration diagram of a third modified example of the Doppler sensor. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0010] 1 is a block diagram showing a signal processing device having a moving object detection device according to this embodiment. The signal processing device 1 includes a Doppler sensor 2 that functions as a moving object detection device, and a microcontroller unit (MCU) 10. The Doppler sensor 2 includes a transmitting antenna 3, a receiving antenna 4, a voltage-controlled oscillator (VCO) 5, a phase shifter 6, and mixers 7 and 8.

[0011] VCO 5 outputs a constant sine wave (continuous wave) of, for example, 24 GHz to the outside via transmit antenna 3. VCO 5 also outputs the sine wave to phase shifter 6 and mixer 7. Phase shifter 6 shifts the phase of the sine wave from VCO 5 by 90° and outputs it to mixer 8.

[0012] The receiving antenna 4 receives a reflected signal (having a frequency of, for example, 24 GHz + Δf) reflected by a moving object and outputs the reflected signal to mixers 7 and 8. The mixer 7 mixes the sine wave from the VCO 5 with the reflected signal and outputs the result as an I signal to the MCU 10. The mixer 8 mixes the sine wave from the phase shifter 6 with the reflected signal and outputs the result as a Q signal to the MCU 10.

[0013] As a result of the above, the Doppler sensor 2 outputs the frequency difference (Δf) between the reflected signal from the moving object and the sine wave of the VCO 5 as the Doppler effect to the MCU 10. This frequency difference (Δf) is proportional to the speed of the moving object.

[0014] The MCU 10 includes multiplexers (MUX) 11 and 12, AD converters (ADC) 13 and 14, and a signal analysis unit 15. The MUX 11 combines multiple I signals into a single I signal and outputs it to the ADC 13. Note that although FIG. 1 shows one Doppler sensor 2, multiple Doppler sensors may be provided. The ADC 13 converts the I signals into digital signals and outputs the digital signals to the signal analysis unit 15. The MUX 12 combines multiple Q signals into a single Q signal and outputs the digital signal to the ADC 14. The ADC 14 converts the Q signals into digital signals and outputs the digital signals to the signal analysis unit 15. The signal analysis unit 15 analyzes the digital signals corresponding to the I signals and Q signals received from the ADCs 13 and 14 to detect the speed of a moving object and the approach or departure of the moving object.

[0015] The VCO 5, phase shifter 6, and mixers 7 and 8 constitute a quadrature modulation / demodulation circuit that outputs two I and Q signals that are 90 degrees out of phase as Doppler frequency signals based on the signals from the transmitting antenna 3 and receiving antenna 4. The MCU 3 constitutes a detection circuit that detects the approach or departure of a moving object from the substrate and the speed of the moving object based on the I and Q signals.

[0016] FIG. 2 is a diagram showing an example of the I signal and Q signal output from the Doppler sensor 2 when a moving object passes in front of the Doppler sensor 2. Here, the moving object is assumed to be a liquid passing through a pipe. The solid line waveform in FIG. 2 indicates the Q signal, and the dotted line waveform indicates the I signal. The Doppler sensor 2 outputs a signal with a frequency that corresponds to the speed of the moving object.

[0017] For example, when a moving object is approaching the Doppler sensor 2, the Doppler effect causes the receiving frequency to be higher than the transmitting frequency, so the phase of the Q signal leads the phase of the I signal by 90°. Therefore, the signal analysis unit 15 can determine that a moving object is approaching the Doppler sensor 2 when the phase of the Q signal leads the phase of the I signal by 90°.

[0018] On the other hand, when a moving object is moving away from Doppler sensor 2, the Doppler effect causes the receiving frequency to be lower than the transmitting frequency, so the phase of the Q signal lags behind the phase of the I signal by 90°. Therefore, signal analysis unit 15 can determine that a moving object is moving away from Doppler sensor 2 when the phase of the Q signal lags behind the phase of the I signal by 90°.

[0019] The phase relationship between the Q signal and the I signal will always be ±90° even if the frequency changes. If there are no moving objects and only stationary objects, the Q signal and I signal will be 0 Hz.

[0020] 2, the Q signal and I signal cancel each other out because the moving object simultaneously approaches and moves away from the Doppler sensor 2. For example, the Q signal and I signal from the moving object at points A and B are detected, causing them to cancel each other out. For this reason, when the moving object is a fluid (water flow, powder passing through a pipe, etc.) or a continuous body (thread, metal wire, plate, etc.), it is desirable to extract only the signal component of either the approach or departure of the moving object.

[0021] Therefore, in order to extract only the signal components of either the approaching or moving away of a moving object, the Doppler sensor 2 of this embodiment has an opening between the transmitting antenna and the receiving antenna mounted on the substrate to allow the moving object to pass through.

[0022] FIG. 3 is a configuration diagram of the Doppler sensor 2, and FIG. 4 is a cross-sectional schematic diagram of the substrate. The Doppler sensor 2 is mounted on a substrate 20. As shown in FIG. 3, a transmitting antenna 3 and a receiving antenna 4 are provided on the surface of the substrate 20 (i.e., on the same plane of the substrate 20). The transmitting antenna 3 and the receiving antenna 4 are arranged so as to point upward. In the example of FIG. 3, the transmitting antenna 3 and the receiving antenna 4 are array antennas that can accurately detect moving objects by narrowing their directivity, but they do not necessarily have to be array antennas. Note that it is preferable that the number of transmitting antennas 3 and the number of receiving antennas 4 are the same so that the radio wave strength (signal strength) transmitted and received by the transmitting antenna 3 and the receiving antenna 4 are at the same level.

[0023] In FIG. 3 , the substrate 20 has an opening 21 between the transmitting antenna 3 and the receiving antenna 4, through which the thread 50 serving as the moving object passes. The opening 21 is preferably provided in approximately the center of the substrate 20 between the transmitting antenna 3 and the receiving antenna 4. The approximately center of the substrate 20 includes not only the center of the substrate 20 but also deviations due to manufacturing errors. By providing the opening 21 in approximately the center of the substrate 20 between the transmitting antenna 3 and the receiving antenna 4, the speed of the moving object and the approach or departure of the moving object can be detected with high accuracy.

[0024] The opening 21 is a through-hole that penetrates the substrate 20, but it may also be a notch 22 that is formed by removing a portion of the substrate 20 between the transmitting antenna 3 and the receiving antenna 4, as described below (see FIG. 5). In either the through-hole or the notch, it is possible to extract only the signal component of either the approach or departure of a moving object. The moving object may also be a discontinuous object such as a ball or a stone.

[0025] In FIG. 3, the thread 50 is disposed perpendicular to the substrate 20 and the opening 21, but the moving direction of the moving body toward the surface of the substrate 20 is linear and constant and does not need to change. In this case, the moving body does not approach and move away simultaneously. For example, the moving direction of the moving body toward the surface of the substrate 20 does not need to be perpendicular, and may be inclined relative to the surface of the substrate 20 as long as it is linear and constant. The moving direction of the moving body toward the surface of the substrate 20 changes, for example, when the thread 50 is curved or when the thread 50 is curved so as to alternately approach and move away from the opening 21.

[0026] 3 and 4, the transmitting antenna 3 and the receiving antenna 4 are not provided on the back surface of the substrate 20, and therefore the separation of the thread 50 cannot be detected on the back surface of the substrate 20. For this reason, the Doppler sensor 2 only observes the Q signal and the I signal when the thread 50 approaches. Note that when the thread 50 moves from the back surface to the front surface of the substrate 20, only the Q signal and the I signal when the thread 50 separates are observed. Therefore, the Q signal and the I signal do not cancel out due to the approach and separation of a moving object occurring simultaneously, making signal analysis easier.

[0027] As shown in FIG. 4, the substrate 20 is a laminated substrate having, for example, a first layer 20a, a second layer 20b, and a third layer 20c. An opening 21 penetrates the first layer 20a, the second layer 20b, and the third layer 20c. The first layer 20a has a transmitting antenna 3 and a receiving antenna 4. The second layer 20b is a GND layer that blocks radio waves from the transmitting antenna 3 from diffusing toward the third layer 20c. The third layer 20c has a voltage-controlled oscillator (VCO) 5, a phase shifter 6, and mixers 7 and 8. Note that one or more layers may be provided between the first layer 20a and the second layer 20b and between the second layer 20b and the third layer 20c. In this case, for example, any of the voltage-controlled oscillator (VCO) 5, the phase shifter 6, and the mixers 7 and 8 may be included in a layer provided between the second layer 20b and the third layer 20c instead of the third layer 20c.

[0028] 5 is a configuration diagram of a first modified example of the Doppler sensor 2. In FIG. 5, the opening 21 is not a through-hole but a notch 22 formed by removing a portion of the substrate 20 between the transmitting antenna 3 and the receiving antenna 4. The moving object is a plate 51, which passes through the gap in the notch 22. A continuous object such as the thread 50 or the plate 51 is at least longer than the thickness of the substrate 20. For an object longer than the thickness of the substrate 20, the transmitting antenna 3 and the receiving antenna 4 are provided only on the front surface of the substrate 20 to prevent the Doppler sensor 2 from simultaneously observing both the approaching and separating portions.

[0029] FIG. 6 is a structural diagram of a second modified example of the Doppler sensor 2. In FIG. 6, the cylindrical body 23 passes through the opening 21. A moving object such as a fluid passes through the inside of the cylindrical body 23. In this case, the fluid can be prevented from splashing. The cylindrical body 23 is made of a material that transmits radio waves, such as a non-conductor such as plastic or resin. This is because if a material that blocks radio waves, such as metal, is used, it would be impossible to observe the moving object inside the cylindrical body 23. The opening 21 may be a notch formed by removing a portion of the substrate.

[0030] 5 and 6, when the mobile object moves from the front surface to the back surface of the substrate 20, only the Q signal and I signal when the mobile object approaches are observed. Conversely, when the mobile object moves from the back surface to the front surface of the substrate 20, only the Q signal and I signal when the mobile object moves away are observed. In this way, by being able to extract only the approaching or leaving signals for any substance, it becomes easier to analyze the signal state of movement.

[0031] FIG. 7A is a configuration diagram of a reference example of the Doppler sensor 2, and FIG. 7B is a configuration diagram of a third modified example of the Doppler sensor 2. As shown in FIG.

[0032] 7(A), if the thread 50 is curved so as to alternately approach and move away from the opening 21, the approach and movement of the thread 50 will occur simultaneously, causing the Q signal and the I signal to cancel each other out, making signal analysis difficult. For this reason, the moving direction of the moving body relative to the surface of the substrate 20 must be kept linear and constant and not changeable.

[0033] Therefore, as shown in FIG. 7(B), a radio wave absorber 60 houses the substrate 20 of the Doppler sensor 2 and blocks the intrusion of radio waves from outside. The radio wave absorber 60 is, for example, a box-shaped case, which may be a metal case or a plastic case with a radio wave absorbing sheet attached. Openings 61 are provided on the top and bottom surfaces of the radio wave absorber 60 to allow the thread 50 to pass through. The movement direction of the thread 50 inside the radio wave absorber 60 is linear and constant. Furthermore, in areas where the radio wave absorber 60 provides sufficient isolation from the Doppler sensor 2, the movement direction of the thread 50 is not restricted.

[0034] 7(B), the movement of the yarn 50 only inside the radio wave absorber 60 is detected, so there is no cancellation of the Q signal and the I signal due to simultaneous approach and departure, making signal analysis easier. In addition, the movement direction of the yarn 50 outside the radio wave absorber 60 can be ignored.

[0035] As shown in Figure 7(B), when the radio wave absorber 60 houses the substrate 20 of the Doppler sensor 2, the moving body is not limited to the thread 50, but may be a fluid (water flow, powder) or a continuous body (metal wire, plate, etc.).

[0036] 6, a cylindrical body 23 penetrating through the opening 21 may be provided inside the radio wave absorber 60. The cylindrical body 23 may also be extended to the outside of the radio wave absorber 60 through the opening 61. In this case, bending of a moving body such as the thread 50 inside the cylindrical body 23 can be prevented, and therefore only an approaching or leaving signal can be extracted.

[0037] As described above, according to this embodiment, the substrate 20 of the Doppler sensor 2 has the opening 21 between the transmitting antenna 3 and the receiving antenna 4 to allow a moving object to pass through, so that it is possible to easily extract only the signal component of either the approaching or leaving of a moving object. Therefore, cancellation of the Q signal and the I signal due to the simultaneous occurrence of approaching and leaving of a moving object does not occur, making signal analysis easier. Furthermore, because only the approaching or leaving signal can be extracted, it is possible to simplify the analytic signals (Q signal and I signal).

[0038] The present invention is not limited to the above-described embodiment, and can be implemented in various modified forms without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0039] 1. Signal Processing Device 2 Doppler sensors 3 transmitting antennas 4 receiving antennas 5. Voltage Controlled Oscillator (VCO) 6 Phase Shifter 7,8 Mixer 10 Microcontroller Unit (MCU) 20 Substrate 21 Aperture

Claims

1. a substrate having a front surface and a back surface; a transmitting antenna provided on the surface of the substrate and transmitting radio waves toward a moving object; a receiving antenna provided on the surface of the substrate and configured to receive radio waves reflected by the moving object; The mobile object detection device is characterized in that the substrate has an opening between the transmitting antenna and the receiving antenna to allow the mobile object to pass through.

2. 2. The moving body detection device according to claim 1, further comprising a radio wave absorber that houses the substrate.

3. 3. The moving body detection device according to claim 1, wherein the opening is a through-hole that penetrates the substrate or a notch that is formed by removing a part of the substrate.

4. 3. The moving body detection device according to claim 1, further comprising a cylindrical body that passes through the opening, and the moving body passes through the inside of the cylindrical body.

5. 3. The mobile body detection device according to claim 2, wherein the mobile body is configured so that, inside the radio wave absorber, the direction of movement of the mobile body toward the surface of the substrate is linear.

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