Communication device and object detection device

Abstract

The present invention provides a communication device and an object detection device that can improve both the average radiation efficiency and peak gain of radio waves. [Solution] The communication device comprises an antenna, a circuit board that causes the antenna to transmit radio waves, and a reflective member having an aperture that reflects the radio waves, wherein both the average radiation efficiency and peak gain of the radio waves are greater than the average radiation efficiency and peak gain of the radio waves when it is assumed that a member identical to the reflective member is located at the position of the aperture.

Description

Technical Field

[0001] The present disclosure relates to a communication device and an object detection device.

Background Art

[0002] In recent years, as disclosed in Patent Document 1 below, as an example of an object detection device, development of a vehicle detection device installed in a parking lot has been carried out. Generally, a parking lot has a plurality of parking areas drawn with white lines on asphalt. In such a parking lot, a plurality of vehicle detection devices are provided at the central positions of the plurality of parking areas in a one-to-one relationship. When each vehicle detection device detects that a vehicle is present in the parking area where it is provided, it transmits a vehicle detection signal that can identify the presence of the vehicle to another communication device.

[0003] In this case, the vehicle detection device also functions as a communication device. The communication device as this object detection device transmits a vehicle detection signal to another communication device by radio communication that emits radio waves from an antenna. The communication device disclosed in Patent Document 1 below can improve the peak gain of radio waves by having a reflecting member that reflects radio waves between the ground and the antenna.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Generally, in parking lots, increasing the height of the vehicle detection device may obstruct vehicle movement, so it is preferable to keep the distance between the antenna and the reflector small. However, reducing the distance between the antenna and the reflector reduces the average radiation efficiency of the radio waves due to coupling between the antenna and the reflector via radio waves. In other words, according to the technology disclosed in Patent Document 1, it is not possible to improve both the average emissivity and peak gain of the radio waves.

[0006] This disclosure has been made in view of the above-mentioned issues. The object of this disclosure is to provide a communication device and an object detection device that can improve both the average radiation efficiency and peak gain of radio waves. [Means for solving the problem]

[0007] The communication device of this disclosure comprises an antenna, a circuit board that causes the antenna to transmit radio waves, and a reflective member having an aperture that reflects the radio waves, wherein both the average radiation efficiency and peak gain of the radio waves are greater than the average radiation efficiency and peak gain of the radio waves that would be obtained if a member identical to the reflective member were located at the position of the aperture. [Brief explanation of the drawing]

[0008] [Figure 1] This diagram illustrates how the communication device of Embodiment 1 functions as an object detection device. [Figure 2] This diagram shows the communication device of Embodiment 1 installed in a parking lot. [Figure 3] This is a perspective view showing the external appearance of the communication device according to Embodiment 1. [Figure 4] This is an exploded perspective view of the communication device according to Embodiment 1. [Figure 5] This is an upper perspective view of the circuit board of the communication device according to Embodiment 1. [Figure 6] This is a lower perspective view of the circuit board of the communication device according to Embodiment 1. [Figure 7] This is a plan view of the reflective member of the communication device according to Embodiment 1. [Figure 8] This is an enlarged view of the vicinity of the opening of the reflective member of the communication device according to Embodiment 1. [Figure 9] This is a cross-sectional view along the line IX-IX in Figure 3. [Figure 10] This is a plan view of a modified example of the reflective member according to Embodiment 1. [Figure 11] This is an enlarged view of the vicinity of the opening of a modified example of Embodiment 1. [Figure 12] This is an exploded perspective view of the communication device according to Embodiment 2. [Figure 13] This is a plan view of the reflective member of the communication device according to Embodiment 2. [Figure 14] This graph compares the radio waves emitted by the communication device of Embodiment 2 with the radio waves emitted by the communication devices of Comparative Examples 1 and 2. [Figure 15] This graph compares the average radiation efficiency of the communication device in Embodiment 2 with the average radiation efficiency of the communication devices in Comparative Examples 1 and 2. [Figure 16] This graph compares the peak gain of the radio waves of the communication device in Embodiment 2 with the peak gain of the radio waves of the communication devices in Comparative Examples 1 and 2. [Modes for carrying out the invention]

[0009] Hereinafter, the communication device and object detection device of the embodiments of this disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements will be denoted by the same reference numerals, and redundant descriptions will not be repeated.

[0010] (Embodiment 1) The communication device 1, which functions as an object detection device in Embodiment 1, will be explained using Figures 1 to 16. The communication device 1 includes a vehicle sensor unit that detects a vehicle as an object, but this will be explained later.

[0011] First, the usage situation of the communication device 1 according to this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a diagram for explaining that the communication device 1 according to this embodiment functions as a vehicle sensor. FIG. 2 is a diagram showing the situation where the communication device 1 according to this embodiment is installed in a parking lot.

[0012] As shown in FIG. 1, the communication device 1 emits a radar wave R. Also, as shown in FIG. 2, the communication device 1 is installed on the ground at approximately the center of each of a plurality of parking areas PA in the parking lot 100. If the power of the reflected wave of the radar wave R emitted by itself received by the communication device 1 is a certain level or more, the communication device 1 determines that there is a vehicle M in the parking area PA. If the power of the reflected wave of the radar wave R emitted by itself received by the communication device 1 is below a certain level, the communication device 1 determines that there is no vehicle M in the parking area PA. The communication device 1 transmits a detection signal that can identify the presence or absence of the vehicle M in the parking area PA as a radio wave RW to another communication device C. In this embodiment, the frequency of the radio wave RW output by the communication device 1 is in the 920 MHz band. Note that, in this embodiment, the other communication device C is a parking fee settlement machine set near the entrance of the parking lot 100.

[0013] Based on the detection signals received from a plurality of communication devices 1, the other communication device C determines whether there is a vehicle M in each of the plurality of parking areas PA. Thereby, based on the determination result of the presence or absence of the vehicle M in each parking area PA, for example, when there is a vehicle M in all of the plurality of parking areas PA, the other communication device C communicates with the display panel D and causes the display panel D to display that it is a full occupancy state. Also, the other communication device C communicates with the gate G at the entrance of the parking lot 100 and closes the gate G to prevent the next vehicle M from entering the parking lot 100. On the other hand, when there is no vehicle M in any of the plurality of parking areas PA, the other communication device C causes the display panel D to display the number (not shown) marked on the parking area PA where there is no vehicle M. Thereby, the vehicle M trying to enter the parking lot 100 next is guided to the parking area PA where there is no vehicle M.

[0014] Next, the schematic configuration of the communication device 1 according to Embodiment 1 will be described with reference to FIGS. 3 to 6. FIG. 3 is a perspective view showing the appearance of the communication device 1 according to Embodiment 1. FIG. 4 is an exploded perspective view of the communication device 1 according to the present embodiment. FIGS. 5 and 6 are perspective views of the upper and lower sides of the circuit board 20. As described above, the communication device 1 in the present embodiment includes a vehicle sensor unit installed outdoors. The communication device 1 transmits the vacancy information of the parking lot to the display panel D.

[0015] As shown in FIGS. 3 and 4, the communication device 1 includes a housing 10, a circuit board 20, an antenna 30, a power supply unit 40, a waterproof packing 45, and a reflecting member 50. Hereinafter, the positive Z-axis direction may be referred to as up, upward, or upper side, and the negative Z-axis direction may be referred to as down, downward, or lower side.

[0016] The housing 10 houses the circuit board 20, the antenna 30, and the power supply unit 40. The housing 10 includes an upper housing 12 and a lower housing 14. The upper housing 12 has a dome shape. The lower housing 14 has a cylindrical or ring shape with an open upper surface and a closed lower surface.

[0017] The lower housing 14 has a storage space Rb for storing the circuit board 20 inside. The lower housing 14 of the housing 10 has a mounting surface 146. The mounting surface 146 is a surface of the lower housing 14 facing the upper housing 12. The housing 10 is installed on the ground so that the mounting surface 146 is substantially parallel to the ground. Thereby, the reflecting member 50 is positioned between the antenna 30 and the ground. The ground is an example of the installation surface of the communication device 1, and the installation surface on which the communication device 1 is installed may be a surface such as a floor, a wall, a pillar, or a roof instead of the ground.

[0018] The lower housing 14 further has an upper end portion 142 and a side surface 144. The waterproof packing 45 is disposed at the upper end portion 142. The side surface 144 has a cylindrical shape. The side surface 144 is a portion that is fitted to the upper housing 12. The side surface 144 faces a part of the back surface of the upper housing 12.

[0019] As shown in Figures 5 and 6, the circuit board 20 has a substrate 22 and a vehicle sensor unit 24. The substrate 22 has a first mounting surface 222 and a second mounting surface 224. The first mounting surface 222 is located on the upper side. The second mounting surface 224 is located on the lower side. Electronic circuit components are mounted on the circuit board 20. Specifically, the vehicle sensor unit 24 is mounted on the first mounting surface 222. The vehicle sensor unit 24 has a vehicle sensor 242 and a vehicle sensor substrate 244.

[0020] The vehicle sensor 242 detects whether or not a vehicle is parked in the parking area PA when the communication device 1 is connected. In other words, the vehicle sensor 242 detects the availability of parking areas PA. The vehicle sensor 242 is mounted on the vehicle sensor board 244. The vehicle sensor board 244 is mounted on board 22. More specifically, the vehicle sensor board 244 is mounted on the first mounting surface 222 of board 22. The circuit board 20 is placed on top of the power supply unit 40 housed in the lower housing 14.

[0021] The antenna 30 is mounted on the substrate 22. More specifically, the antenna 30 is mounted on the second mounting surface 224 of the substrate 22. The antenna 30 radiates radio waves RW as shown in Figure 2.

[0022] When the upper housing 12 is fitted with the lower housing 14 with the waterproof packing 45 in between, as shown in Figure 1, the surface of the lower housing 14 is covered by the upper housing 12, and the circuit board 20, antenna 30, and power supply unit 40 are enclosed within the housing 10.

[0023] The power supply unit 40 supplies power to the circuit board 20.

[0024] The waterproof packing 45 has a ring shape. The waterproof packing 45 is sandwiched between the upper housing 12 and the lower housing 14. The waterproof packing 45 prevents water from entering the inside of the housing 10.

[0025] The reflective member 50 is located outside the housing 10. The reflective member 50 is plate-shaped. The outer circumference of the reflective member 50 is rectangular. The reflective member 50 is located on the mounting surface 146 side of the antenna 30. In other words, the reflective member 50 is located below the antenna 30. The reflective member 50 is made of, for example, metal. The metal may be, for example, aluminum or iron. However, the reflective member 50 may be made of any material that reflects the radio waves RW radiated from the antenna 30.

[0026] In this embodiment, the reflective member 50 reflects the radio waves RW emitted by the antenna 30 to the side opposite to the mounting surface 146. In other words, the reflective member 50 reflects the radio waves RW emitted by the antenna 30 to the side opposite to the ground. In this embodiment, the reflective member 50 reflects the radio waves RW emitted by the antenna 30 upward (see Figure 9).

[0027] The reflective member 50 has an opening 52, three first through holes 54, and four second through holes 56. The opening 52 is a single elongated hole. The elongated hole is rectangular, but may be rhombic, circular, or elliptical. The first through holes 54 are holes that penetrate the reflective member 50 in the thickness direction.

[0028] A fixing member (not shown) is inserted into each of the three first through holes 54. The fixing member is, for example, a bolt. By inserting the fixing members (not shown) into each of the three first through holes 54, the upper housing 12 is fixed to the reflective member 50. In other words, the reflective member 50 is attached to the mounting surface 146. As a result, the housing 10 is fixed to the reflective member 50.

[0029] The second through-hole 56 is a hole that penetrates the reflective member 50 in the thickness direction. A fixing member (not shown) is inserted into each of the four second through-holes 56. This fixing member is, for example, a bolt. In this way, the reflective member 50 is fixed to the ground. As a result, the housing 10 is fixed to the ground via the reflective member 50. In other words, the communication device 1 is fixed to the ground.

[0030] The reflective member 50 will be described in detail using Figures 7 to 9. Figure 7 is a plan view of the reflective member 50. Figure 8 is an enlarged view of the vicinity of the opening 52 of the reflective member 50. Figure 9 is a cross-sectional view along the line IX-IX in Figure 1. In Figure 9, the straight arrow indicates the direction of propagation of the radio wave RW.

[0031] As shown in Figures 7 and 8, the opening 52 is located in the antenna region R1 when the antenna 30 is viewed along the Z-axis direction. The antenna region R1 is the projection area of ​​the antenna 30 in the Z-axis direction on the surface of the reflector member 50. The Z-axis direction is the direction intersecting the mounting surface 146. In this embodiment, the Z-axis direction is perpendicular to the mounting surface 146.

[0032] As shown in Figure 9, the reflector 50 reflects the radio waves RW radiated downward by the antenna 30 upward. In the antenna region R1, the reflector 50 has an aperture 52. The reflector 50 is not present in the region directly below the antenna 30, where coupling (interference) between the antenna 30 and the reflector 50 is likely to occur. As a result, coupling (interference) between the antenna 30 and the reflector 50 can be suppressed by the radio waves RW.

[0033] On the other hand, a reflective member 50 is present in areas other than the antenna region R1. Therefore, the radio waves RW radiated from the antenna 30 toward the ground can be reflected by the reflective member 50. As a result, the radiation efficiency of the antenna 30 can be increased. Furthermore, according to the communication device 1 of this embodiment, both the average radiation efficiency and peak gain of the radio waves RW are greater than those of the radio waves RW when it is assumed that the same material as the reflective member 50 is present at the position of the aperture 52. In other words, the shape and size of the aperture 52 of the reflective member 50 are designed to achieve such average radiation efficiency and peak gain of the radio waves RW.

[0034] In this embodiment, the inner circumference of the opening 52 overlaps with the outer circumference of the antenna 30 in a plan view. Therefore, the reflecting member 50 is absent in the entire region directly below the antenna 30, where coupling (interference) between the antenna 30 and the reflecting member 50 is likely to occur. As a result, coupling (interference) between the antenna 30 and the reflecting member 50 due to radio wave RW can be suppressed more reliably. Consequently, the radiation efficiency of the antenna 30 can be increased.

[0035] Furthermore, the opening 52 is a single rectangular elongated hole. Therefore, the opening 52 can be provided with a simple structure. As a result, the opening 52 can be easily provided in the reflective member 50.

[0036] In addition, the aperture 52 has the same shape as the antenna 30 in a plan view. Therefore, it is easy to improve both the average radiation efficiency and peak gain of the radio wave RW emitted from the communication device 1.

[0037] Furthermore, the housing 10 is fixed to the ground (installation surface) via the reflective member 50. Therefore, the reflective member 50 can function as a mounting plate to the ground (installation surface). Consequently, the housing 10 can be easily fixed to the ground (installation surface). As a result, the communication device 1 can be easily fixed to the ground (installation surface).

[0038] Furthermore, the reflective member 50 is plate-shaped. Therefore, it is possible to suppress an increase in the height of the communication device 1. If the height of the communication device 1 increases, there is a risk that the underside of the vehicle M will come into contact with the communication device 1. With the communication device 1 according to this embodiment, it is possible to suppress an increase in the height of the communication device 1, and thus the risk of the vehicle M coming into contact with the communication device 1 can be reduced.

[0039] Specifically, the distance between the antenna 30 and the aperture 52 is less than half a wavelength of the radio wave RW. Therefore, according to the communication device 1 of this embodiment, even under conditions where the average radiation efficiency of the radio wave RW tends to decrease, both the average radiation efficiency and the peak gain of the radio wave RW emitted from the communication device 1 can be effectively improved.

[0040] A modified example of the communication device 1 of Embodiment 1 will be described using Figures 10 and 11.

[0041] Figure 10 is a plan view of the modified reflective member 50. Figure 11 is an enlarged view of the vicinity of the modified opening 52.

[0042] As shown in Figures 10 and 11, the reflective member 50 differs from the reflective member 50 of Embodiment 1 in that the opening 52 is slightly larger than the region R1. In other words, the inner circumference of the opening 52 surrounds the outer circumference of the antenna 30 in a plan view. As a result, even if the horizontal position (XY direction) of the antenna 30 varies when the housing 10 is attached to the reflective member 50, the reflective member 50 can be made absent in the region directly below the antenna 30. Consequently, coupling (interference) between the antenna 30 and the reflective member 50 can be suppressed more reliably.

[0043] In this modified example, the aperture 52 has the same shape (including similar shapes) as the antenna 30 in a plan view. Therefore, it is easy to improve both the average radiation efficiency and peak gain of the radio wave RW emitted from the communication device 1.

[0044] (Embodiment 2) The communication device 1 of Embodiment 2 will be described using Figures 12 to 16. Note that the same aspects as the communication device 1 of Embodiment 1 will not be repeated below. The following will mainly describe the differences between Embodiment 2 and Embodiment 1.

[0045] Figure 12 is an exploded perspective view of the communication device 1 of this embodiment. Figure 13 is a plan view of the reflective member 50 of the communication device 1 of this second embodiment.

[0046] As can be seen from Figures 12 and 13, the communication device 1 of this embodiment differs from the communication device 1 of Embodiment 1 in that the opening 52 of the reflective member 50 is circular.

[0047] Figure 14 is a graph comparing the radio wave RW emitted by the communication device 1 of this embodiment with the radio waves emitted by the communication devices 1 of Comparative Examples 1 and 2. Figure 15 is a graph comparing the average radiation efficiency of the radio waves of the communication device 1 of this embodiment with the average radiation efficiency of the radio waves of the communication devices of Comparative Examples 1 and 2. Figure 16 is a graph comparing the peak gain of the radio wave RW of the communication device 1 of this embodiment with the peak gain of the radio waves of the communication devices of Comparative Examples 1 and 2. However, the values ​​in Figures 15 and 16 are based on the range of angles 0 to 90 degrees and angles 270 to 360 (=0) degrees in Figure 14, that is, when the communication device 1 is installed on a roughly horizontal surface, and only the radio waves directed towards space that are effective for actual communication are considered, ignoring the radio waves directed towards the ground that are not effective for actual communication.

[0048] The communication device of Comparative Example 1 does not have a reflective member. The communication device of Comparative Example 2 has a reflective member that is the same shape and size as the reflective member 50 of the communication device 1 of Embodiment 2, but this reflective member does not have an opening.

[0049] From Figures 14 to 16, it can be seen that, in the communication device 1 of this embodiment, the reflective member 50 has an aperture 52, and therefore both the average radiation efficiency and peak gain of the radio wave RW are improved. Furthermore, because the aperture 52 is circular, both the average radiation efficiency and peak gain of the radio wave RW can be improved almost uniformly in all 360 degrees in a plan view.

[0050] In this embodiment, at least a portion of the aperture 52 is positioned to overlap with the antenna 30 in a plan view. This configuration allows for improved design flexibility of the reflective member 50 and the aperture 52, while also improving both the average radiation efficiency and peak gain of the radio wave RW emitted from the communication device 1.

[0051] The features of the communication device 1, which also functions as an object detection device in this embodiment, and the effects obtained therefrom are summarized below.

[0052] (1) The communication device 1 comprises an antenna 30, a circuit board 20, and a reflector 50. The antenna 30 transmits radio waves RW. The circuit board 20 causes the antenna 30 to transmit radio waves RW. The reflector 50 has an aperture 52 and reflects radio waves RW. Both the average radiation efficiency and peak gain of the radio waves RW are greater than those of the radio waves RW that would occur if the same material as the reflector 50 were present at the position of the aperture 52. With such a communication device 1, by providing an aperture 52 in the reflector 50, both the average radiation efficiency and peak gain of the radio waves RW emitted from the communication device 1 can be improved.

[0053] (2) The average radiation efficiency and peak gain of the radio waves reflected by the reflecting member 50 may be greater than the average radiation efficiency and peak gain of the radio waves reflected by the reflecting member 50 if the same member as the reflecting member 50 were located at the position of the aperture 52. With such a communication device 1, by providing an aperture 52 in the reflecting member 50, both the average radiation efficiency and peak gain of the radio waves RW reflected by the reflecting member 50 can be improved.

[0054] (3) At least a portion of the antenna 30 may be positioned so as to overlap with the aperture 52 in a plan view. This makes it easier to improve both the average radiation efficiency and peak gain of the radio wave RW radiated from the communication device 1.

[0055] (4) The inner circumference of the aperture 52 may surround the outer circumference of the antenna 30 in a plan view, or it may overlap with the outer circumference of the antenna 30. This makes it possible to improve both the average radiation efficiency and peak gain of the radio wave RW radiated from the communication device 1 by the aperture 52 of the reflecting member 50 with a simple structure.

[0056] (5) The aperture 52 may have the same shape as the antenna 30 in a plan view. This makes it easier to improve both the average radiation efficiency and peak gain of the radio wave RW radiated from the communication device 1.

[0057] (6) The aperture 52 may be circular in plan view. This improves both the average radiation efficiency and peak gain of the radio wave RW almost uniformly in all 360 degrees.

[0058] (7) At least a portion of the aperture 52 may be positioned to overlap with the antenna 30 in a plan view. This improves both the average radiation efficiency and peak gain of the radio wave RW radiated from the communication device 1 while increasing the design freedom of the reflector 50 and the aperture 52.

[0059] (8) The distance between the antenna 30 and the aperture 52 may be less than or equal to half a wavelength of the radio wave. This makes it possible to effectively improve both the average radiation efficiency and peak gain of the radio wave RW emitted from the communication device 1, even under conditions where the average radiation efficiency of the radio wave RW emitted from the communication device 1 tends to decrease.

[0060] (9) The object detection device of this embodiment includes a car sensor unit 24, which is an example of an object sensor that detects a car, which is an example of an object. In this case, the circuit board 20 may cause the antenna 30 to transmit a detection signal that identifies that an object has been detected when an object is detected by the object sensor. This makes it possible to improve both the average radiation efficiency and peak gain of the radio wave RW emitted by the object detection device.

[0061] (Other) The aforementioned opening 52 is formed by a single through hole, but it may also be formed by a matrix of multiple through holes arranged randomly. [Explanation of Symbols]

[0062] 1. Communication device 20 Circuit boards 24. Vehicle sensor unit (object sensor) 30 Antennas 50 Reflective material 52 Aperture

Claims

1. Antenna and, A circuit board that causes the aforementioned antenna to transmit radio waves, It comprises a reflective member having an opening and reflecting the radio waves, Both the average radiation efficiency and peak gain of the aforementioned radio waves are greater than those of the aforementioned radio waves when it is assumed that the same member as the reflecting member is present at the position of the aperture. Communication device.

2. The communication device according to claim 1, wherein both the average radiation efficiency and peak gain of the radio waves reflected by the reflecting member are greater than the average radiation efficiency and peak gain of the radio waves reflected by the reflecting member if the same member as the reflecting member were present at the position of the aperture.

3. At least a portion of the antenna is provided in a position that overlaps with the opening in a plan view. The communication device according to claim 1.

4. The inner circumference of the opening, in a plan view, surrounds the outer circumference of the antenna or overlaps with the outer circumference of the antenna. The communication device according to claim 1.

5. The opening has the same shape as the antenna in a plan view. The communication device according to claim 1.

6. The aforementioned opening is circular in plan view. The communication device according to claim 1.

7. At least a portion of the aforementioned opening is positioned to overlap with the antenna in a plan view. The communication device according to claim 1.

8. The communication device according to claim 1, wherein the distance between the antenna and the aperture is less than or equal to half a wavelength of the radio wave.

9. A communication device according to any one of claims 1 to 8, It includes an object sensor that detects objects, The circuit board causes the antenna to transmit a detection signal that identifies the detection of an object when the object is detected by the object sensor. Object detection device.

Images