JP7455468B2 - plate antenna - Google Patents

Description

The present invention relates to a plate-shaped antenna that can obtain a desired half-value angle in a miniaturized plate-shaped antenna.

A short range communication system called DSRC (Dedicated Short Range Communication) is known. DSRC is a wireless communication system with a radio wave range of several meters to several tens of meters, and is used in ETC (Electronic Toll Collection Systems) and ITS (Intelligent Transport Systems). There is. ETC is a system that automatically pays tolls when a car passes through a toll gate on an expressway by communicating between an antenna installed at the gate and an on-vehicle device installed on the vehicle. When ETC is adopted, there is no need to stop at the tollgate, which greatly reduces the time it takes for a car to pass through the gate. Therefore, traffic congestion near toll gates can be alleviated, and exhaust gas can be reduced.

Furthermore, ITS is a transportation system that combines systems that make cars intelligent, such as car navigation systems (hereinafter referred to as "car navigation systems"), and systems that make roads intelligent, such as wide-area traffic control systems. For example, some car navigation systems are capable of linking with VICS (registered trademark) (Vehicle Information and Communication System). In such cases, the VICS (registered trademark) center uses ITS to edit and disseminate information on general roads collected by the police and information on expressways collected by the Metropolitan Expressway Corporation, Japan Highway Corporation, and others. When the car navigation system receives this information, it can search for routes to bypass traffic jams and display them on the monitor.

A plate antenna is generally used as an antenna for DSRC or ETC. The configuration of a conventional plate antenna 100 is shown in FIGS. 20 to 22. 20 is a plan view showing the configuration of a conventional plate antenna 100, FIG. 21 is a bottom view showing the configuration of the conventional plate antenna 100, and FIG. 22 is a side view showing the configuration of the conventional plate antenna 100. It is a diagram.
In the conventional plate antenna 100 shown in these figures, a square metal excitation element 110 is placed on a square metal earth element 111 with a spacer 114 interposed therebetween at a predetermined interval. has been done. The excitation element 110 is provided with degenerate separation elements at the lower left and upper right, and the degenerate separation elements are configured with a right triangular C-cut. Power is supplied to the excitation element 110 from a power supply cable 112. In this case, the power supply pin 110a is provided at a predetermined position of the excitation element 110, and the power supply pin 110a is inserted into an insulating spacer 114 and soldered to the center conductor of the power supply cable 112 on the back surface of the grounding element 111. etc. are connected. Further, the shield conductor of the power supply cable 112 is connected to the back surface of the ground element 111 by soldering or the like, so that the plate antenna 100 is supplied with power by the power supply cable 112. That is, a transmission signal from a communication device connected to one end of the power supply cable 112 is fed to the plate antenna 100 and radiates right-handed circularly polarized waves, and the right-handed circularly polarized wave is received by the plate antenna 100. The signal propagates through the power supply cable 112 and is supplied to the communication device.

To give an example of dimensions when the plate antenna 100 is an antenna for ETC using the 5.8 GHz band, the length W22 of the horizontal width and vertical width, which are the same dimensions of the excitation element 110 shown in FIG. The length W21 of the horizontal and vertical widths, which are approximately 21 mm and the same dimensions as the grounding element 111 shown in FIG. The length D21 is approximately 3 mm. Here, when the free space wavelength of 5.8 GHz is λ, W21 is approximately 0.5λ, and W22 is approximately 0.41λ. The graph of FIG. 23 shows the radiation intensity characteristics with respect to the azimuth angle at a frequency of 5.8 GHz when such dimensions are used. Referring to FIG. 23, the peak value of the radiation intensity is +7.4 dB and its azimuth angle is +2.80°, and the half-value angle, which is the azimuth angle range where the radiation intensity decreases by 3 dB, is 71.32°. It has been obtained.

Next, in the conventional plate antenna 100, changes in the half-power angle when the width and length W21 of the grounding element 111 are changed will be described.
FIG. 24 shows the characteristics of the half-power angle with respect to the length W21 of the grounding element 111 at a frequency of 5.8 GHz in the conventional plate antenna 100 having the above dimensions except for the length W21 of the grounding element 111. FIG. 24 shows the half-value angle characteristics when the length W21 of the grounding element 111 is changed from 20 mm to 50 mm. Referring to FIG. 24, as the length W21 is increased from 20 mm to 50 mm, the half-value angle becomes approximately 73°. It can be seen that the radiation beam gradually narrows as the angle decreases from about 63° to about 63°. When the length W21 exceeds about 31 mm, the target half-value angle of 70° is obtained. Here, if the free space wavelength of 5.8 GHz is λ, the length W21 of about 31 mm is expressed as about 0.6λ. That is, by setting the length W21 of the grounding element 111 to approximately 0.6λ or more, it becomes possible to obtain directivity with a half-value angle of 70° or less.
Examples of the above-described conventional plate antenna 100 are described in Patent Documents 1 to 3, respectively.

Japanese Patent Application Publication No. 2002-135045 JP2005-269518A Japanese Patent Application Publication No. 2008-109252

Recently, when the wavelength of the design frequency is λ, even if the size of the antenna part of the plate antenna is reduced to about 0.5λ or less, a planar antenna that can obtain a half-power angle of 70° or less is required. ing. A half-value angle of 70° or less allows directivity that prevents radio waves from being received from directions other than the desired direction. However, in the conventional plate antenna 100, if the horizontal and vertical widths W21 of the grounding element 111 are approximately 26 mm (approximately 0.5λ), the half-value angle exceeds 70°, and the half-value angle is less than 70°. In order to obtain focused beam directivity, in the conventional plate antenna 100, the width of the grounding element is greater than 0.6λ, and reduced to approximately 0.5λ or less, as shown in FIG. This means that it cannot be downsized. In other words, in order to control the required directivity, a grounding element that exceeds the size required for miniaturization is required, and it is difficult to obtain the desired half-power angle in a miniaturized plate antenna. There was a problem that it became difficult.
Therefore, an object of the present invention is to provide a plate-shaped antenna that can obtain a desired half-power angle in a miniaturized plate-shaped antenna.

The plate-shaped antenna of the present invention capable of achieving the above object of the present invention has a rectangular upper plate and a lower surface consisting of a first side plate consisting of four erected walls erected from four edges of the upper plate. A box-shaped lower case with an open top, a second side plate consisting of a box-shaped upper case with an opening, a rectangular lower plate, and four standing walls erected from the four edges of the lower plate. a storage case configured by fitting the upper case into the lower case so as to close an opening of the upper case and an opening of the lower case; a rectangular grounding element; and a rectangular grounding element; an antenna module that is housed in the storage case and that includes a rectangular excitation element that is smaller than the ground element and that is arranged on the element at a first predetermined interval, and a power supply cable that supplies power to the excitation element; a rectangular parasitic element smaller than the grounding element fixed thereon, the parasitic element being arranged below at a second predetermined distance from the grounding element in the antenna module housed in the storage case; The most important feature is that

Further, in the plate antenna of the present invention, an insulating spacer having a height of the first predetermined distance is provided between the grounding element and the excitation element, and a spacer having a height of the first predetermined distance is provided, and a second spacer protrudes upward from the upper surface of the spacer. The main feature is that the excitation element is positioned and fixed to the spacer by fitting one boss into a positioning hole provided in the excitation element.
Further, in the plate antenna of the present invention, the earthing element is positioned by fitting the protrusion projecting downward from the lower surface of the spacer into the insertion hole provided in the earthing element. The main feature is that the driving element and the grounding element are fixedly fixed, thereby positioning the excitation element and the grounding element.
Furthermore, in the plate antenna of the present invention, the antenna module is attached to the lower case by fitting an insertion wall erected from the lower plate into a positioning groove provided on a side edge of the grounding element. The main feature is that it can be positioned and fixed.
Furthermore, in the plate antenna of the present invention, the parasitic element is positioned by fitting a second boss projecting upward from the lower plate into a fitting hole provided in the parasitic element. The main feature is that the parasitic element is fixed to the lower case, so that the parasitic element is positioned on the ground element.
Furthermore, in the plate antenna of the present invention, a second engagement means is formed that protrudes downward from the inner surface of the first side plate, and a concave engagement means is formed on the inner surface of the second side plate. When the upper case is inserted into the lower case, the second engaging means is engaged with the engaging portion, and the upper case is fixed to the lower case. It has the following characteristics.
Furthermore, in the plate antenna of the present invention, the parasitic element has a rectangular shape, and when the wavelength of the design frequency is λ, one side of the parasitic element that provides a predetermined half-value angle The main feature is that the length can be shortened to about 0.21λ.
Furthermore, in the plate antenna of the present invention, the grounding element has a square shape, and when the wavelength of the design frequency is λ, the length of one side of the grounding element is such that a predetermined half-power angle is obtained. The main feature is that it can be shortened to about 0.48λ.

In the plate antenna of the present invention, excitation elements smaller than the ground element are arranged on the ground element at predetermined intervals, and parasitic elements smaller than the ground element are arranged below the ground element, so that the wavelength of the design frequency is λ Even if the size of the grounding element, which is larger than the driven element and the parasitic element, is reduced to approximately 0.5λ or less, a plate that can obtain a half-value angle that provides directivity that does not receive radio waves from directions other than the desired direction. It can be a shaped antenna.

FIG. 1 is a plan view showing the configuration of a plate antenna according to an embodiment of the present invention. FIG. 1 is a side view showing a cross-sectional view of the configuration of a plate antenna according to an embodiment of the present invention. 1 is an exploded perspective view showing the configuration of a plate antenna according to an embodiment of the present invention; FIG. FIG. 2 is a plan view showing the configuration of an antenna module in the plate antenna of the present invention. It is a bottom view showing the composition of the antenna module in the plate antenna of the present invention. FIG. 3 is a rear view showing the configuration of the antenna module in the plate antenna of the present invention. FIG. 2 is a left side view showing the configuration of an antenna module in the plate antenna of the present invention. FIG. 2 is a right side view showing the configuration of an antenna module in the plate antenna of the present invention. FIG. 1 is a plan view, a side view, and a front view showing the structure of an upper case in the plate antenna of the present invention. FIG. 1 is a perspective view, a plan view, and a side view showing the configuration of a lower case in the plate antenna of the present invention. FIG. 1 is a perspective view, a plan view, a front view, and a side view showing the structure of a spacer in a plate antenna of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, a front view, a left side view, and a right side view showing the configuration of an excitation element in a plate antenna of the present invention. FIG. 3 is a plan view, a side view, and a rear view showing the configuration of a grounding element in the plate antenna of the present invention. FIG. 1 is a plan view and a side view showing the configuration of a parasitic element in a plate antenna of the present invention. FIG. 1 is a perspective view, a bottom view, and a side view showing the configuration of a holding metal fitting in a plate antenna of the present invention. FIG. 2 is a perspective view showing the configuration of a feeding cable in the plate antenna of the present invention. FIG. 3 is a diagram showing radiation intensity characteristics with respect to azimuth angle in the plate antenna of the present invention. FIG. 3 is a diagram showing the characteristics of the half-value angle with respect to the length of the parasitic element in the plate antenna of the present invention. FIG. 3 is a diagram showing the characteristics of the half-value angle with respect to the width of the grounding element in the plate antenna of the present invention. FIG. 2 is a plan view showing the configuration of a conventional plate antenna. FIG. 2 is a bottom view showing the configuration of a conventional plate antenna. FIG. 2 is a side view showing the configuration of a conventional plate antenna. FIG. 3 is a diagram showing radiation intensity characteristics with respect to azimuth angle in a conventional plate antenna. FIG. 7 is a diagram showing the characteristics of the half-value angle with respect to the length of the grounding element in a conventional plate antenna.

[Example of the present invention]
The configuration of a plate antenna 1 according to an embodiment of the present invention is shown in FIGS. 1 and 2. FIG. 1 is a plan view showing the configuration of the plate antenna 1, and FIG. 2 is a bottom view showing the configuration of the plate antenna 1 in an aa cross-sectional view taken along the aa line, which is the center line. It is a diagram.
The plate antenna 1 according to the embodiment of the present invention shown in these figures includes a storage case 0 consisting of an upper case 10 and a lower case 11 made of synthetic resin, and an antenna module 5 and a parasitic element 16 are installed in the storage case 0. is stored. The storage case 0 has a square cross section, the length of one side is W1, and the height of the storage case 0 is H1. The antenna module 5 includes an excitation element 13, a spacer 14, a grounding board 15, and a feeding cable 12, the details of which will be described later. As shown in FIG. 2, the excitation element 13 is spaced apart from the ground board 15 by a predetermined distance corresponding to the height of the spacer 14, and the ground board 15 is a printed circuit board. A grounding element 15a made of a print is formed on the front and back sides. Further, a power supply circuit is formed on the back surface of the ground board 15, and power is supplied from this power supply circuit to the excitation element 13 via a power supply pin. The antenna consisting of the excitation element 13 and the ground element 15a can transmit and receive circularly polarized waves. Furthermore, the plate antenna 1 according to the present invention has a characteristic configuration in that it includes a parasitic element 16, which is arranged under the back surface of the grounding board 15 at a predetermined distance. Parasitic element 16 is arranged so as to be in contact with the upper surface of lower case 11 .

[Description of each component in the plate antenna according to the present invention]
Before explaining FIGS. 3 to 8, each component constituting the plate antenna 1 according to the embodiment of the present invention will be explained with reference to FIGS. 9 to 16.
The configuration of the upper case 10 is shown in FIGS. 9(a), 9(b), and 9(c). 9(a) is a plan view showing the structure of the upper case 10, FIG. 9(b) is a side view showing the structure of the upper case 10, and FIG. 9(c) is a front view showing the structure of the upper case 10. It is a diagram.
The upper case 10 shown in these figures is made of synthetic resin and has a box-like shape with an open bottom. The upper case 10 has a square-shaped upper plate 10a and a rectangular ring-shaped structure that stands diagonally from each of the four edges around the upper plate 10a so that the width gradually increases downward from the upper plate 10a. It has a wall 10b. The four corners of the standing wall 10b are rounded, and a fitting piece 10c with a rounded cross section is provided from each corner, projecting substantially vertically downward. Further, there is provided a presser piece 10e in which a semicircular groove is formed that projects substantially vertically downward from the substantially central edge of one standing wall 10b. Further, in the standing wall 10b on which the holding piece 10e is provided, engaging claws 10d are provided which project downward substantially vertically from the inner surface on both sides of the holding piece 10e, and the two adjacent to this standing wall 10b Engagement pawls 10d are provided that protrude substantially vertically downward from each of the inner surfaces near the corners of the two standing walls 10b. Note that the engaging claw 10d is not provided on the standing wall 10b that faces the standing wall 10b on which the holding piece 10e is provided. At the tip of each engagement claw 10d, a tapered inward claw whose width gradually increases toward the top plate 10a is formed.

The structure of the lower case 11 is shown in FIGS. 10(a), 10(b), and 10(c). 11(a) is a perspective view showing the structure of the lower case 11, FIG. 11(b) is a plan view showing the structure of the lower case 11, and FIG. 10(c) is a side view showing the structure of the lower case 11. It is a diagram.
The lower case 11 shown in these figures is made of synthetic resin and has a box-like shape with an open top. The lower case 11 includes a square lower plate 11a, and a rectangular ring-shaped standing wall 11b that stands approximately perpendicular to the lower plate 11a from each of the four peripheral edges of the lower plate 11a. ing. Each corner of the standing walls 11b is rounded, and an insertion wall 11g of a predetermined length toward the center is vertically provided at approximately the center of the three standing walls 11b forming a U-shape. There is. A rectangular cut-out insertion section 11e with a substantially semicircular lower end is provided approximately at the center of the remaining standing wall 11b, and two opposing sections located inside this insertion section 11e are provided. A rectangular plate-shaped clamping piece 11h is provided vertically erected from the bottom plate 11a. Further, a pair of elongated cylindrical bosses 11d are vertically provided at substantially the center of the lower plate 11a and spaced apart from each other. Further, a concave engaging portion 11f is formed on the inner surface of each standing wall 11b at a position corresponding to the position of the engaging claw 10d on the upper case 10. The engaging portion 11f is a recessed portion having a corner portion that does not easily come off when the claw of the engaging claw 10d is engaged.

The configuration of the spacer 14 is shown in FIGS. 11(a), (b), (c), and (d). 11(a) is a perspective view showing the structure of the spacer 14, FIG. 11(b) is a plan view showing the structure of the spacer 14, and FIG. 11(c) is a front view showing the structure of the spacer 14. , FIG. 11(d) is a side view showing the structure of the spacer 14.
The spacer 14 shown in these figures is made of synthetic resin and includes a cross-shaped main body portion 14a. The main body portion 14a has four elongated rod-shaped portions having a rectangular cross section and substantially the same length, and are arranged substantially perpendicular to each other, and the main body portion 14a is formed with a height D2. In the main body portion 14a of the spacer 14, insertion holes 14c each having a rectangular cross section are formed between two adjacent rod-shaped portions. Further, an elongated cylindrical boss 14d is formed at the center of the upper surface of the cross-shaped main body part 14a and one of the rod-shaped parts in which the insertion hole 14c is not formed, and from the center of the lower surface of the cross-shaped main body part 14a. A protruding elongated cylindrical protrusion 14b is formed.

The configuration of the excitation element 13 is shown in FIGS. 12(a), (b), (c), and (d). 12(a) is a perspective view showing the configuration of the excitation element 13, FIG. 12(b) is a front view showing the configuration of the excitation element 13, and FIG. 12(c) is a left side view showing the configuration of the excitation element 13. 12(d) is a right side view showing the configuration of the excitation element 13. FIG.
The excitation element 13 shown in these figures is electrically conductive and can be created by processing a metal plate. The excitation element 13 consists of a main body part 13a having a square shape with a side width of W2, and a positioning hole 13c is formed approximately in the center of the main body part 13a. A positioning hole 13c is formed. A pair of bosses 14d formed on the upper surface of the main body 14a of the spacer 14 are inserted into the two positioning holes 13c, respectively. Thereby, the excitation element 13 is positioned relative to the spacer 14 and attached to the spacer 14. Further, two elongated holes 13b are formed in the main body portion 13a. One long hole 13b is formed substantially parallel to one side of the main body 13a, the other long hole 13b is formed substantially parallel to the other adjacent side, and the two long holes 13b are formed substantially perpendicular to the main body 13a. is formed. Further, each long hole 13b is formed by punching, and the long and thin piece punched out of the long hole 13b is bent downward to be perpendicular to the main body portion 13a. In this case, two pieces bent from the elongated hole 13b formed substantially perpendicularly constitute the first power supply pin 18a and the second power supply pin 18b. Note that when the pair of bosses 14d of the spacer 14 are inserted into the pair of positioning holes 13c, the first power supply pin 18a and the second power supply pin 18b are respectively inserted into the two insertion holes 14c formed in the spacer 14. Become so. Note that the length of the first power supply pin 18a and the second power supply pin 18b is L4.

FIGS. 13(a), 13(b), and 13(c) show the configuration of the grounding board 15. 13(a) is a plan view showing the structure of the grounding board 15, FIG. 13(b) is a side view showing the structure of the grounding board 15, and FIG. 13(c) is a rear view showing the structure of the grounding board 15. It is a diagram.
The grounding board 15 shown in these figures is composed of a square printed circuit board with one side having a width of W3 and a thickness of D3, with corners cut diagonally. The earth element 15a is constituted by the metal foil formed on the entire surface of the front surface, and the earth element 15a is constituted by the metal foil formed on the back surface of the earth substrate 15 except for the central part. . The grounding element 15a on the front surface of the grounding board 15 and the grounding element 15a on the back surface are connected through a plurality of through holes 15f. Three insertion holes 15c each having a circular cross section are formed in the grounding board 15 so as to correspond to each corner of a substantially right triangle.The insertion hole 15c formed approximately in the center has a protrusion formed on the lower surface of the spacer 14. 14b is inserted, and the first power supply pin 18a and the second power supply pin 18b of the excitation element 13 protruding from the insertion hole 14c of the spacer 14 are inserted into the remaining two insertion holes 15c, respectively. As a result, the spacer 14 and the ground board 15 are positioned and fixed, and the excitation element 13 mounted on the spacer 14 and the ground board 15 are positioned to face each other with a predetermined distance D2. Further, small positioning grooves 15b each having a rectangular cross section are formed approximately at the center of each of the three edges of the grounding board 15. Near the center of the remaining edge of the grounding board 15, two mounting holes 15e each having an elongated rectangular cross section are formed at a predetermined interval and facing each other in parallel. Further, shallow rectangular notches 15g are formed on both sides of this edge and near the corners of two edges adjacent to this edge. The engaging claws 10d of the upper case 10 can be inserted into these four notches 15g.

A diamond-shaped land 15h from which metal foil has been removed is formed at the center of the back surface of the grounding board 15, and a diamond-shaped 90° phase circuit 15g is formed to surround this land 15h. The 90° phase circuit 15g is constituted by a 90° hybrid circuit and has terminals P1, P2, P3, and P4. A grounding element 15a is formed to surround the 90° phase circuit 15g. The insertion hole 15c formed in the center is provided in the land 15h, and the remaining two insertion holes 15c are provided in the terminals P2 and P3, respectively, which have a phase difference of 90° from each other in the 90° phase circuit 15g. . As a result, power feeding signals having a phase difference of 90 degrees are supplied to the first power feeding pin 18a and the second power feeding pin 18b of the excitation element 13 inserted through the remaining two insertion holes 15c. In this case, the power supply signal input to the terminal P1 is output from the terminal P2 with a 90° phase delay, and is output from the terminal P3 with a 180° phase delay.

FIGS. 14(a) and 14(b) show the configuration of the parasitic element 16. 14(a) is a plan view showing the configuration of the parasitic element 16, and FIG. 14(b) is a side view showing the configuration of the parasitic element 16.
The parasitic element 16 shown in these figures is electrically conductive and can be created by processing a metal plate. The parasitic element 16 has a rectangular shape, and includes a main body portion 16a having a short side length L1, a long side length L2, and a thickness D4. Fitting holes 16c each having a circular cross section are formed on both sides of the center of the main body portion 16a. Bosses 11d formed in the lower case 11 are inserted into the fitting holes 16c, respectively. By inserting it, it is possible to position it with respect to the lower case 11 and attach the parasitic element 16. Further, a shallow rectangular notch 16b is formed on one of the long sides of the main body portion 16a. An insertion wall 11g formed in the lower case 11 is fitted into the notch 16b, so that the parasitic element 16 can be positioned with respect to the lower case 11.

The configuration of the cable clamp 17 is shown in FIGS. 15(a), 15(b), and 15(c). 15(a) is a perspective view showing the structure of the cable clamp 17, FIG. 15(b) is a bottom view showing the structure of the cable clamp 17, and FIG. 15(c) is a side view showing the structure of the cable clamp 17. It is a diagram.
The cable clamp 17 shown in these figures is made by processing a metal plate, and has a U-shaped cross section. The cable clamp 17 is composed of a planar top portion 17a located in the center and a pair of legs 17b that are bent vertically so that both sides of the top portion 17a are substantially parallel to each other. The cable clamp 17 is inserted into the mounting hole 15e on the front surface of the ground board 15 from the tip of the leg 17b, and the part of the shield conductor of the power supply cable 12 is inserted between the legs 17b that have passed through the mounting hole 15e. By pinching, the shield conductor of the power supply cable 12 is connected to the ground element 15a. The width of the cable clamp 17 is L5, the outer length of the legs 17b is L6, and the height is H2.

FIG. 16 shows a perspective view showing the configuration of the power supply cable 12.
The power supply cable 12 shown in FIG. 16 includes a central conductor 12d arranged on the central axis, an insulating cylinder 12c made of resin with good high frequency characteristics that holds the central conductor 12d, and an insulating cylinder so as to cover the insulating cylinder 12c. It is composed of a cylindrical shield conductor provided concentrically on the body 12c and a synthetic resin outer sheath 12a formed in a cylindrical shape to protect the shield conductor. A metal shield ring 12b having a circular cross section is fitted into the shield conductor from which the outer sheath 12a has been removed.

[Assembly of plate antenna according to the embodiment of the present invention]
Next, the procedure for assembling the plate antenna 1 according to the embodiment of the present invention will be explained with reference to FIGS. 3 to 8. FIG. 3 is an exploded perspective view showing the configuration of the plate antenna 1 according to the embodiment of the present invention, and FIG. 4 is a plan view showing the configuration of the antenna module in the plate antenna 1 according to the embodiment of the present invention. , FIG. 5 is a bottom view showing the configuration of the antenna module in the plate antenna 1 according to the embodiment of the present invention, and FIG. 6 is a rear view showing the configuration of the antenna module in the plate antenna 1 according to the embodiment of the present invention. , FIG. 7 is a left side view showing the structure of the antenna module in the plate antenna 1 according to the embodiment of the present invention, and FIG. 8 is a right side view showing the structure of the antenna module in the plate antenna 1 according to the embodiment of the present invention. It is.

When assembling the plate antenna 1 according to the embodiment of the present invention, as shown in FIG. 13c is inserted, and the excitation element 13 is mounted on the spacer 14. In this attachment, the excitation element 13 is positioned and attached on the spacer 14, and the two power supply pins 18a and 18b, the first power supply pin 18a and the second power supply pin 18b, protruding from the back surface of the excitation element 13 are attached to the spacer 14, respectively. The first power supply pin 18a and the second power supply pin 18b, which are inserted into the insertion hole 14c and penetrated through the insertion hole 14c, protrude from the back surface of the spacer 14. Next, the spacer 14 to which the excitation element 13 is attached is placed on the front surface of the grounding board 15, and the protrusion 14b formed on the lower surface of the spacer 14 is inserted into the insertion hole formed in the center of the grounding board 15. 15c, and the first power supply pin 18a and second power supply pin 18b protruding from the back surface of the spacer 14 are inserted into each of the two remaining insertion holes 15c of the ground board 15. Next, on the back surface of the ground board 15, the first power supply pin 18a and the second power supply pin 18b are soldered to the terminals P2 and P3 of the 90° phase circuit 15g, respectively. Thereby, the excitation element 13 and the spacer 14 are positioned and fixed to the earth substrate 15, and the excitation element 13, the spacer 14, and the earth substrate 15 are fixed so as to be integrated.

Next, the pair of legs 17b of the cable clamp 17 are inserted into the mounting hole 15e from the front surface of the ground board 15, and the top portion 17a is soldered around the mounting hole 15e on the front surface. Then, the power supply cable 12 is placed on the back surface of the ground board 15, and the shield ring 12b is inserted between the leg portions 17b of the cable clamp 17 that has passed through the ground board 15, and is inserted into the shield conductor at the tip of the power supply cable 12. Insert and hold. Next, the center conductor 12d of the power supply cable 12 is connected to the terminal P1 of the 90° phase circuit 15g by soldering, and the shield conductor sandwiched between the pair of legs 17b, the shield ring 12b, and the leg 17b are soldered. Attach. As a result, the power supply cable 12 is fixed in a predetermined position, and the power supply signals supplied from the power supply cable 12 are outputted from the first power supply pin 18a and the second power supply pin 18b with a phase difference of 90° from each other. . This feed signal having a phase difference of 90° is fed to the excitation element 13 via the first feed pin 18a and the second feed pin 18b, and circularly polarized waves are radiated from the excitation element 13. In this case, since the power supply signal from the second power supply pin 18b is delayed in phase by 90 degrees from the power supply signal from the first power supply pin 18a, a right-handed circularly polarized wave is emitted from the excitation element 13. Further, the right-handed circularly polarized reception signal received by the excitation element 13 propagates through the power supply cable 12 and is supplied to the communication device to which the power supply cable 12 is connected.

In this way, the antenna module 5 shown in FIGS. 4 to 8 is assembled. Note that although the parasitic element 16 is illustrated in FIGS. 5 to 8, the parasitic element 16 is not attached to the antenna module 5. As will be described later, the parasitic element 16 is attached to the lower case 11, but the parasitic element 16 is shown in FIGS. 5 to 8 for convenience of explanation. In the antenna module 5, the distance between the upper surface of the ground substrate 15 and the excitation element 13 is D2, which is the height of the spacer 14, and the distance between the lower surface of the earth substrate 15 and the parasitic element 16 is D1. That is, the distance between the excitation element 13 and the earth element 15a is D2, and the distance between the parasitic element 16 and the earth element 15a is D1.

Next, the two bosses 11d of the lower case 11 are fitted into the fitting holes 16c of the parasitic element 16, and the insertion wall 11g of the lower case 11 is fitted into the notch 16b formed in the parasitic element 16. In this way, the parasitic element 16 placed in contact with the upper surface of the lower case 11 is attached to the lower case 11. Thereby, the parasitic element 16 is positioned and attached to the lower case 11. Then, the assembled antenna module 5 is placed on the lower case 11 to which the parasitic element 16 is attached, and housed in the lower case 11. At this time, the insertion walls 11g of the lower case 11 are fitted into the three positioning grooves 15b of the ground board 15, and the ground board 15, that is, the antenna module 5, is positioned and housed in the lower case 11, and the ground board 15 is It also comes to be positioned on the parasitic element 16. Further, the power supply cable 12 is inserted into the insertion portion 11e of the lower case 11 from above, and the power supply cable 12 is pulled out from the lower case 11 to the outside. Next, the upper case 10 is placed on the antenna module 5, and the upper case 10 is fitted into the lower case 11. At this time, the four fitting pieces 10c of the upper case 10 are fitted into the respective rounded corners of the lower case 11, and the four engaging claws 10d of the upper case 10 are formed on the ground board 15. The four engaging portions 11f of the lower case 11 are engaged with the four engaging portions 11f of the lower case 11. As a result, the upper case 10 is tightly fixed to the lower case 11, so that the upper case 10 and the lower case 11 cannot be easily separated, and the plate antenna 1 according to the embodiment of the present invention is assembled.

[Dimensions and electrical characteristics of the plate antenna according to the present invention]
In the plate antenna 1 of the embodiment of the present invention described above, when the design frequency is 5.8 GHz, the width W2 of one side of the excitation element 13 is about 19 mm, and the width W3 of one side of the grounding board 15 is about 26 mm. , the short side length L1 of the parasitic element 16 is about 17 mm, the long side length L2 is about 20 mm, the distance D2 between the excitation element 13 and the grounding element 15a is about 2 mm, and the distance between the parasitic element 16 and the grounding element is about 2 mm. 15a is approximately 3 mm. Further, the length W1 of one side of the storage case 0 of the plate antenna 1 at this time is approximately 29 mm, and the height H1 thereof is approximately 10 mm. Furthermore, the length and width of the cross-shaped body portion 14a of the spacer 14 are made slightly shorter than the width W2 of one side of the excitation element 13, and the height D2 of the spacer 14 is approximately 2 mm, and the first power feeding pin 18a of the excitation element 13 The length L4 with respect to the second power feeding pin 18b is approximately 4.2 mm, the thickness D3 of the grounding board 15 is approximately 1 mm, the thickness D4 of the parasitic element 16 is approximately 0.2 mm, and the cable clamp 17 The width L5 of the leg portions 17b is approximately 3 mm, the outer length L6 of the leg portions 17b is approximately 3.5 mm, and the height H2 is approximately 4.18 mm. Here, when the free space wavelength of 5.8 GHz is λ, the length W2 is approximately 0.37λ, the length W3 is approximately 0.5λ, the length L1 is approximately 0.33λ, and the length L2 is approximately 0. .41λ, the length D1 is approximately 0.058λ, and the length D2 is approximately 0.039λ.

FIG. 17 shows radiation intensity characteristics with respect to azimuth angle at a frequency of 5.8 GHz in the plate antenna 1 of the embodiment of the present invention having the above dimensions. Referring to FIG. 17, +4.22 dB is obtained as the peak value of the radiation intensity, and the azimuth angle at this time is +0.4°. In addition, the half-value angle, which is the range of azimuth angles until the radiation intensity is attenuated by 3 dB, was obtained as 63.55°, and when the length of one side of the earthing element 15a is 26 mm, the beam is narrowed down. It can be seen that radiation intensity characteristics with directivity with a half-value angle of 70° or less can be obtained. That is, in the plate antenna 1 according to the embodiment of the present invention, even if the size of the antenna module 5 of the plate antenna 1 is reduced to about 0.5λ or less, when the wavelength of the design frequency is λ, A plate antenna that can obtain the following half-power angle can be used. As a result, in the plate antenna 1 according to the embodiment of the present invention, even if the size of the antenna module 5 is reduced to approximately 0.5λ or less, the directivity can be such that radio waves are not received from directions other than the desired direction. . Note that the radiation intensity characteristics with respect to the azimuth angle shown in FIG. 17 have almost the same characteristics in the frequency band of 5.79 GHz to 5.84 GHz.

Next, in the plate antenna 1 according to the embodiment of the present invention, a change in the half-power angle when the size of the parasitic element 16 is changed will be considered.
In the plate antenna 1 of the embodiment of the present invention when the dimensions are as described above except for the length L1 of the short side of the parasitic element 16, the length L1 of the short side of the parasitic element 16 at a frequency of 5.8 GHz. FIG. 18 shows the characteristics of the half-value angle with respect to the angle. FIG. 18 shows the half-value angle characteristics when the length L1 is changed from 5 mm to 20 mm. Referring to FIG. 18, as the length L1 increases from 5 mm to 20 mm, the half-value angle changes from about 71° to about 63°. It can be seen that the radiation beam gradually narrows as the beam becomes smaller. When the length L1 becomes approximately 11 mm, the target half-power angle of 70° is obtained. Here, if the free space wavelength of 5.8 GHz is λ, the length L1 of about 11 mm is expressed as about 0.21λ. That is, in the plate antenna 1 according to the embodiment of the present invention, even if the length L1 of the short side of the parasitic element 16 is shortened to approximately 0.21λ, which is 0.5λ or less, and the size is reduced, the half value of 70° or less It can be a plate-shaped antenna that provides an angle. As a result, in the plate antenna 1 of the embodiment of the present invention, even if the short side length L1 of the parasitic element 16 is shortened to about 0.21λ, which is 0.5λ or less, and the antenna is made smaller, It is possible to set the directionality so that it does not receive radio waves from. Note that the characteristics of the half-value angle with respect to the length L1 shown in FIG. 18 are almost the same in the frequency band of 5.79 GHz to 5.84 GHz.

Next, in the plate antenna 1 according to the embodiment of the present invention, a change in the half-power angle when the size of the grounding element 15a is changed will be considered. Since the dimensions of the grounding element 15a are the same as those of the grounding board 15, the length of one side of the grounding element 15a is W3.
In the planar antenna 1 of the embodiment of the present invention when the dimensions are as described above except for the length W3 of one side of the grounding element 15a, the half value of the length W3 of one side of the grounding element 15a at a frequency of 5.8 GHz. The corner characteristics are shown in FIG. FIG. 19 shows the half-value angle characteristics when the length W3 of one side of the grounding element 15a is changed from 20 mm to 50 mm. Referring to FIG. 19, as the length W3 is increased from 20 mm to 50 mm, the half-value angle becomes It can be seen that the radiation beam gradually narrows from about 73° to about 63°. When the length W3 becomes approximately 25 mm, the target half-value angle of 70° is obtained. Here, if the free space wavelength of 5.8 GHz is λ, then the length W3 of about 25 mm is expressed as about 0.48λ. That is, even if the length W3 of one side of the grounding element 15a is shortened to about 0.48λ, which is less than 0.5λ, a plate antenna can be obtained that can obtain a half-value angle of 70° or less. As a result, in the plate antenna 1 according to the embodiment of the present invention, even if the length W3 of one side of the grounding element 15a is shortened to approximately 0.48λ, which is less than 0.5λ, radio waves from directions other than the desired direction can be prevented. It is possible to set the directionality so that it is not affected. Note that the characteristics of the half-value angle with respect to the length W3 shown in FIG. 19 are almost the same in the frequency band of 5.79 GHz to 5.84 GHz.
In this way, even if the length W3 of one side of the earthing element 15a is set to approximately 0.48λ and the earthing element 15a is downsized, a half-value angle of 70°, which is the target half-value angle, can be obtained. In this case, the parasitic element 16 has a short side length L1 of about 0.21λ, which can be made smaller than the grounding element 15a, and the excitation element 13 has a side length W2 of about 0.37λ, which makes it possible to make the parasitic element 16 smaller than the grounding element 15a. It can be made smaller than the element 11. As described above, in the plate antenna 1 according to the present invention, even if the size of the plate antenna is downsized to about 0.5λ or less, when the wavelength of the design frequency is λ, the half value angle is 70° or less. This makes it possible to obtain directivity that does not receive radio waves from directions other than the desired direction.

[Modified example of plate antenna according to the present invention]
In the plate antenna 1 according to the embodiment of the present invention, a function can be added to detect disconnection of the power supply cable 12 or poor connection of parts on the side of the communication device connected to the power supply cable 12. In order to have such a function, a resistance on the order of kΩ called a diagnostic resistance is connected between the print of the 90° phase line 15g and the earth element 15a on the back surface of the earth substrate 15 shown in FIG. 13(a). do. As a result, the current from the center conductor 12d of the power supply cable 12 flows through the 90° phase circuit 15g and the diagnostic resistor to the ground, which is the earthing element 15a. Since the shield conductor of the feed cable 12 is connected to the ground element 15a, the combined resistance of the excitation part of the plate antenna 1 and the diagnostic resistance is visible from the communication device side in a normal state. However, if a disconnection of the power supply cable 12 or a poor connection between components occurs, the combined resistance becomes equivalent to an open end, so that the disconnection of the power supply cable 12 or a poor connection of components can be detected from the communication device side.
Further, the impedance of the 90° phase circuit 15g can be adjusted by connecting an LC chip between the corner of the 90° phase circuit 15g and the ground element 15a.

In the plate antenna according to the embodiment of the present invention described above, the design frequency and dimension values of the plate antenna are not limited to the values described above, and the functions and actions described above in the plate antenna are not limited to the values described above. It is not limited to the values described above as long as the values are such that equivalent functions and effects can be achieved. That is, there is a permissible range above and below the above-mentioned values for the dimension values, and this permissible range is a range in which the plate-shaped antenna exhibits the same functions and actions as those described above.
The plate antenna of the present invention described above can be applied to a DSRC or ETC antenna, and can be used as an ETC antenna using the 5.8 GHz band, which is 5.79 GHz to 5.84 GHz. In this case, as explained above, even if the size of the plate antenna is reduced, it is possible to obtain the target directivity at the half-power angle. In addition, in the plate antenna of the present invention, the 90° phase circuit is configured with a 90° hybrid circuit, but this is not limited to this, and any phase circuit can be used as long as the phase difference between the two outputs is 90°. Can be used. Furthermore, although the plate antenna of the present invention has been described as a right-handed circularly polarized antenna, it may also be a left-handed circularly polarized antenna. In this case, a power supply signal whose phase is delayed by 90 degrees from that of the second power supply pin may be supplied to the first power supply pin from a 90° phase circuit.

0 Storage case, 1 Plate antenna, 5 Antenna module, 10 Upper case, 10a Upper plate, 10b Standing wall, 10c Fitting piece, 10d Engagement claw, 10e Holding piece, 11 Lower case, 11a Lower plate, 11b Standing Wall, 11d Boss, 11e Insertion part, 11f Engagement part, 11g Insertion wall, 11h Holding piece, 12 Power supply cable, 12a Outer cover, 12b Shield ring, 12c Insulating cylinder, 12d Center conductor, 13 Excitation element, 13a Main body part , 13b long hole, 13c positioning hole, 14 spacer, 14a main body, 14b protrusion, 14c insertion hole, 14d boss, 15 earth board, 15a earth element, 15b positioning groove, 15c insertion hole, 15d engagement hole, 15e mounting Hole, 15f Through hole, 15g 90° phase circuit, 15g Notch, 15h Land, 16 Parasitic element, 16a Main body, 16b Notch, 16c Fitting hole, 17 Cable clamp, 17a Top, 17b Leg, 18a First power feeding Pin, 18b Second feeding pin, 100 Plate antenna, 110 Excitation element, 110a Feeding pin, 111 Earthing element, 112 Feeding cable, 114 Spacer

Claims (8)

A box-shaped upper case with an open lower surface, consisting of a rectangular upper surface plate, a first side plate consisting of four standing walls erected from four edges of the upper surface plate, a rectangular lower surface plate, and a rectangular lower surface plate; A box-shaped lower case with an open upper surface and a second side plate consisting of four standing walls erected from four edges of a lower plate, and the opening of the upper case and the opening of the lower case are closed. a storage case configured by fitting the upper case into the lower case so as to
It consists of a rectangular earth element, a rectangular excitation element smaller than the earth element arranged on the earth element at a first predetermined interval, and a power supply cable for feeding power to the excitation element, and is stored in the storage case. An antenna module that is
a rectangular parasitic element smaller than the ground element fixed on the lower surface plate,
The plate-shaped antenna is characterized in that the parasitic element is arranged below at a second predetermined distance from the ground element in the antenna module housed in the storage case. An insulating spacer having a height of the first predetermined distance is provided between the grounding element and the excitation element, and a first boss protruding upward from the upper surface of the spacer is positioned at the first boss provided on the excitation element. The plate antenna according to claim 1, wherein the excitation element is positioned and fixed to the spacer by fitting into the hole. By inserting a protrusion projecting downward from the lower surface of the spacer into an insertion hole provided in the grounding element, the grounding element is positioned and fixed to the spacer, thereby connecting the excitation element and the grounding element. 3. The plate antenna according to claim 2, wherein the antenna element is positioned. The antenna module is positioned and fixed to the lower case by inserting an insertion wall erected from the lower plate into a positioning groove provided on a side edge of the grounding element. The plate antenna according to any one of Items 1 to 3. By fitting a second boss protruding upward from the lower plate into a fitting hole provided in the parasitic element, the parasitic element is positioned and fixed to the lower case, so that the parasitic element is positioned and fixed to the lower case. 5. A plate antenna according to claim 4, characterized in that an element is positioned on the ground element. A second engaging means is formed that protrudes downward from the inner surface of the first side plate, and a concave engaging portion is formed on the inner side of the second side plate, and the upper case is connected to the lower case. 6. The upper case is fixed to the lower case by the second engaging means being engaged with the engaging portion when the upper case is inserted into the lower case. plate antenna. The width of one side of the square-shaped excitation element is approximately 19 mm, the length of the long side of the rectangular parasitic element is approximately 20 mm, and the width of one side of the square-shaped grounding element is approximately 19 mm. 26 mm, the first predetermined interval is about 2 mm, and the second predetermined interval is about 3 mm, and when the wavelength of the design frequency is λ, the short length of the parasitic element that provides a predetermined half-power angle is 7. The plate antenna according to claim 1, wherein the length of the side can be shortened to about 0.21λ. The square-shaped excitation element has a width of about 19 mm on one side, the rectangular parasitic element has a long side length of about 20 mm and a short side length of about 17 mm, and the first predetermined interval. is about 2 mm, and the second predetermined interval is about 3 mm, and when the wavelength of the design frequency is λ, the length of one side of the square grounding element that provides a predetermined half-value angle. 7. The plate antenna according to claim 1, wherein the antenna can be shortened to about 0.48λ.

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