JP6601335B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device having a structure for preventing current from leaking from an antenna body to an outer conductor of a coaxial cable.

  When the area of a flat conductor member (hereinafter referred to as a ground portion) that provides a ground potential in the antenna device is insufficient with respect to the wavelength of a radio wave to be transmitted / received (hereinafter referred to as a target wavelength), it occurs in the antenna element. It is known that the image current excited to the ground portion by the radiated current leaks to the outer conductor of the coaxial cable.

  The amount of current leaking to the outer conductor of the coaxial cable tends to increase as the area of the ground portion decreases. When the leakage current to the outer conductor of the coaxial cable becomes large, the characteristics of the antenna device may become unstable due to the length and routing of the coaxial cable, and the antenna may not obtain sufficient gain. That is, in order to sufficiently stabilize the characteristics of the antenna device, a ground portion having an area corresponding to the target wavelength is required.

  In Patent Document 1, a super-top balun having a length corresponding to one-fourth of the target wavelength is electrically connected to the outer conductor of the coaxial cable in order to achieve both a reduction in the size of the ground portion and suppression of leakage current. An antenna device provided is disclosed. By attaching a supper top balun formed so that the electrical length is a quarter of the target wavelength to the outer conductor, the impedance at the open end increases, and leakage current to the outer conductor of the coaxial cable is reduced. Can be suppressed. Note that λ represents the target wavelength.

  The electrical length is the length for radio waves determined by the relative dielectric constant of the dielectric. The length that is electrically a quarter of the target wavelength corresponds to a quarter of the effective wavelength of the radio wave to be transmitted and received.

JP 2000-77932 A

  In the configuration disclosed in Patent Document 1, a super-top balun having a length that is ¼ of the target wavelength is added electrically, so that the size of the antenna device as a whole increases accordingly.

  The present invention has been made based on this situation, and an object of the present invention is to provide an antenna device capable of achieving both a reduction in size of a ground portion and suppression of leakage current.

In order to achieve the object, the present invention is an antenna device comprising an antenna main body (100) for transmitting and receiving radio waves of a predetermined frequency, and a coaxial cable (200) connected to the antenna main body. The antenna body portion has a ground connection point electrically connected to the outer conductor of the coaxial cable, and is electrically connected to the ground portion (20) that is a flat conductor member and the inner conductor of the coaxial cable. A connected radiating element (40, 91, 92), and a grounding element (50), which is a linear conductor element arranged to face the outer edge of the ground part at a predetermined interval, The earth element is formed to have a length corresponding to one half of the target wavelength, which is the wavelength of the radio wave to be electrically transmitted and received, and the earth element is electrically connected to the outer edge of the ground portion at the center. Contact Are, coaxial cable, intersects the ground element in a plan view, and, as the outer conductor is coupled grounding element and the capacitor, characterized in that attached to the antenna body.

  In the above configuration, the ground element is formed so as to have a length corresponding to a half wavelength of the target wavelength. Therefore, the image current generated in the ground portion flows more easily into the earth element than the outer conductor of the coaxial cable. Further, since the earth element is disposed so as to be capacitively coupled to the outer conductor of the coaxial cable, the image current flowing into the earth element returns from the ground connection point to the ground portion through the outer conductor of the coaxial cable.

  As a result, a loop-shaped current path is formed between the portion facing the earth element (hereinafter referred to as the earth facing portion) at the outer edge of the ground portion and the earth element. When the image current generated in the ground part flows back through the above-described current path, the image current is attenuated as heat. As a result, the leakage current to the outer conductor of the coaxial cable is reduced.

  Further, in the above configuration, a balun such as a super top is not necessary to obtain the above effect. Therefore, the enlargement of the whole apparatus accompanying introducing a balun can be suppressed. That is, according to the above configuration, it is possible to achieve both reduction in size of the antenna device and suppression of leakage current to the outer conductor of the coaxial cable.

  In addition, the code | symbol in the parenthesis described in the claim shows the correspondence with the specific means as described in embodiment mentioned later as one aspect, Comprising: The technical scope of this invention is limited is not.

It is an external appearance perspective view of the antenna device 1 of this embodiment. It is a top view of the antenna device 1 of this embodiment. It is sectional drawing of the antenna apparatus 1 in the III-III line | wire shown in FIG. FIG. 4 is an enlarged view of a region indicated by reference numeral IV in FIG. 3. It is the figure which represented notionally the distribution of the image current in a comparison structure. It is the figure which represented notionally the flow of the image current in the antenna device 1 of this embodiment. It is the figure which compared the directivity of the antenna device 1 of this embodiment, and the directivity of a comparison structure. It is a figure showing the effect of this embodiment. FIG. 10 is a diagram illustrating a schematic configuration of an antenna device 1 disclosed as a second modification. FIG. 10 is a diagram illustrating a schematic configuration of an antenna device 1 disclosed as a third modification. FIG. 10 is a diagram illustrating a schematic configuration of an antenna device 1 disclosed as a fourth modification. FIG. 10 is a diagram illustrating a schematic configuration of an antenna device 1 disclosed as a fourth modification. FIG. 10 is a diagram illustrating a schematic configuration of an antenna device 1 disclosed as a modified example 5; FIG. 10 is a diagram illustrating a schematic configuration of an antenna device 1 disclosed as a modified example 5; FIG. 10 is a diagram illustrating a schematic configuration of an antenna device 1 disclosed as a modified example 6;

[Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. The antenna device 1 according to the present embodiment is generally configured to transmit and receive circularly polarized waves having a predetermined frequency according to the same operating principle as a known patch antenna. The frequency of the radio wave to be transmitted / received may be designed as appropriate, and here is 1.575 GHz as an example.

  Of course, the antenna device 1 may be used for only one of transmission and reception. Hereinafter, a radio wave to be transmitted / received is referred to as a target radio wave, and a wavelength of the target radio wave is also referred to as a target wavelength. In this embodiment, since the operating frequency is assumed to be 1.575 GHz, the target wavelength when propagating through the air is about 191 mm.

<Configuration of antenna device 1>
FIG. 1 is an external perspective view showing an example of a schematic configuration of an antenna device 1 according to the present embodiment. A top view of the antenna device 1 is shown in FIG. 3 is a cross-sectional view of the antenna device 1 taken along line III-III shown in FIG.

  The antenna device 1 includes a main body 100 that realizes transmission and reception of a target radio wave, and a coaxial cable 200 as a feeder line. That is, the coaxial cable 200 plays a role of connecting the main body 100 and a wireless communication device (not shown). The radio communication device performs demodulation and the like of a signal received by the antenna device 1 and supplies high-frequency power corresponding to the transmission signal to the antenna device 1.

  The main body 100 includes a substrate 10, a main ground part 20, a sub-ground part 20A, a patch part 40, a support part 30, a ground element 50, and a bridge part 60 as main members.

  The substrate 10 is a plate-like member made of an electrically insulating material (that is, a dielectric) such as resin. In the present embodiment, as an example, the substrate 10 is assumed to be realized using a dielectric having a relative dielectric constant εr = 4.3. Therefore, the target wavelength on the substrate 10 is approximately 110 mm due to the wavelength shortening effect of the substrate 10.

  The main ground portion 20 and the ground element 50 are disposed on one surface (hereinafter referred to as the upper surface) of the substrate 10, and the sub-ground portion 20 </ b> A is disposed on the other surface (hereinafter referred to as the lower surface). Has been placed. The antenna device 1 is used such that the side on which the main ground portion 20 and the patch portion 40 described later are provided is relatively upper, and the side on which the sub-ground portion 20A is provided is relatively lower. .

  In the present embodiment, the shape of the substrate 10 in plan view (hereinafter referred to as a planar shape) is a square shape. Of course, the planar shape of the substrate 10 may not be square. As another configuration, the planar shape of the substrate 10 may be another polygonal shape or a circular shape (including an ellipse). Of course, the shape which combined them may be sufficient. The size and shape of the substrate 10 may be sufficient as long as the main ground portion 20 and the earth element 50 are arranged.

  For convenience, the configuration of the antenna device 1 will be described below by appropriately introducing the concept of a three-dimensional coordinate system having X, Y, and Z axes that are orthogonal to each other. The X axis is an axis parallel to one side of the square substrate 10, and the Y axis is an axis orthogonal to the X axis in a plane parallel to the substrate 10. The Z axis is orthogonal to each of the X axis and the Y axis, and is an axis whose forward direction is from the lower surface to the upper surface of the substrate 10.

  The main ground part 20 is a plate-like (including foil) member made of a conductor such as copper. In the present embodiment, the planar shape of the main ground portion 20 is a square shape. Thereby, the main ground part 20 is provided with the square-shaped outer edge part corresponding to each square side. The main ground portion 20 is disposed on the upper surface of the substrate 10 such that one set of opposite sides is parallel to the X axis and the other set of opposite sides is parallel to the Y axis.

  For convenience, a portion corresponding to one side of the square of the outer edge portion of the main ground portion 20 is referred to as a first outer edge portion 21, and an outer edge portion corresponding to another one side connected to the first outer edge portion 21 is a second edge. The outer edge 22 is used. The first outer edge portion 21 is parallel to the X axis direction, and the second outer edge portion 22 is parallel to the Y axis.

  A support portion 30 and a patch portion 40 are disposed on the main ground portion 20. In the present embodiment, as an example, the length of one side of the main ground portion 20 is formed so as to electrically correspond to one fifth of the target wavelength. The electrical length is the length for the target radio wave determined by the dielectric constant of the dielectric. The length that is electrically 1/5 of the target wavelength is equivalent to 1/5 of the effective wavelength. The electrical length is also referred to as the effective length. In the present embodiment, the planar shape of the main ground portion 20 is a square shape, but is not limited thereto. As another aspect, a rectangle, circular shape, etc. may be sufficient. Here, the center of gravity of the main ground portion 20 is regarded as the center of the main ground portion 20. The center of the main ground portion 20 corresponds to the center of the ground portion described in the claims.

  The sub-ground portion 20 </ b> A is also a plate-like member having the same shape as the main ground portion 20. As shown in FIG. 3, the main ground portion 20 and the sub-ground portion 20 </ b> A are electrically connected by a plurality of ground bridge portions 70. The ground bridge portion 70 is a conductive member for electrically connecting the main ground portion 20 and the sub-ground portion 20A, and is realized using, for example, a short pin or a via provided in the substrate 10. be able to.

  Points P1 and P2 shown in FIG. 2 represent the installation positions of the ground bridge portion 70. In addition, the point which connects the main ground part 20 and 20 A of subground parts may be three or more places. Moreover, the installation location of the ground bridge | crosslinking part 70 which connects the main ground part 20 and 20 A of subground parts should just be designed suitably.

  Further, the sub-ground portion 20A is electrically connected to the outer conductor 220 of the coaxial cable by a conductive member (hereinafter referred to as an outer conductor connecting portion) 80 as shown in FIG. As a result, the main ground portion 20 is electrically connected to the external conductor 220 via the sub-ground portion 20A and the ground bridge portion 70. That is, the main ground unit 20 and the sub-ground unit 20A provide a ground potential (in other words, a ground potential) in the antenna device 1.

  A point P3 shown in FIG. 2 represents the position of a point (hereinafter referred to as a grounding point) connecting the sub-ground portion 20A and the outer conductor 220 of the coaxial cable. The position of the grounding point P3 corresponds to the position of the external conductor connecting portion 80. The external conductor connecting portion 80 may be a commercially available coaxial cable mounting pin or solder, for example. The outer conductor connecting portion 80 also plays a role of fixing the coaxial cable 200 to the main body portion 100.

  A connection point between the ground bridge portion 70 located closest to the external conductor connection portion 80 (the ground point P3) and the main ground portion 20 corresponds to a ground connection point described in the claims. Specifically, in this embodiment, the point P1 corresponds to a ground connection point. In addition, it is preferable that the ground bridge portion 70 that provides the ground connection point is disposed as close as possible to the external conductor connection portion 80 in a plan view. That is, it is preferable that the points P1 and P3 are as close as possible. In addition, it is more preferable that the ground bridge portion 70 that provides the ground connection point and the external conductor connection portion 80 are provided at positions that overlap in plan view.

  The support portion 30 is a plate-like member made of ceramics having a relative dielectric constant of about 16. The support part 30 is a member for disposing the patch part 40 so as to face the main ground part 20 at a predetermined interval. The support part 30 should just play this role, and the shape of the support part 30 is not restricted to plate shape. The support part 30 may be a plurality of pillars that support the main ground part 20 and the patch part 40 so as to face each other at a predetermined interval.

  Moreover, in this embodiment, although the support part 30 shall be formed using ceramics as an example, it is not restricted to this. In addition, you may implement | achieve using resin etc. However, in order to shorten the wavelength and reduce the size of the patch unit 40, it is preferable to be realized using a material having a relative dielectric constant of 10 or more, for example. In the present embodiment, it is assumed that the effective wavelength at the support portion 30 is 50 mm by adopting ceramics as the material of the support portion 30.

  The patch part 40 is a plate-like member made of a conductor such as copper. The patch part 40 is disposed to face the main ground part 20 via the support part 30 so as to be parallel (including substantially parallel). The patch unit 40 corresponds to the radiating element recited in the claims.

  The shape of the patch portion 40 is a shape in which a cutout portion 41 is provided in a diagonal pair of squares. The notch 41 has a structure for emitting circularly polarized waves, and corresponds to a so-called degenerate separation element or perturbation element. The area of the portion cut from the original square by the notch 41 may be an area determined by a well-known degenerate separation method.

  The length of one side of the patch part 40 is electrically half the length of the target wavelength. Here, since the wavelength of the target radio wave is shortened by the support unit 30, the physical length of one side of the patch unit 40 is about 25 mm. In addition, the length of one side here is the shape when the notch 41 is ignored, that is, the length of one side in a square.

  In the present embodiment, the planar shape of the patch portion 40 is a shape in which the cutout portion 41 is provided in a square shape, but is not limited thereto. As another configuration, the planar shape of the patch portion 40 may be a rectangular shape, or may be a shape other than a rectangle (for example, a circle or an octagon).

  A point P4 shown in FIG. 2 represents a point (hereinafter referred to as a feeding point) where the patch unit 40 is electrically connected to the inner conductor (so-called core wire) 210 of the coaxial cable 200. The internal conductor 210 and the patch part 40 may be directly connected, or may be indirectly connected via a microstrip line, a conductive pin, or a via provided in the substrate 10.

  In the present embodiment, as an example, the power supply point P4 is provided at the center of the patch unit 40. However, the present invention is not limited to this. The position of the feeding point P4 may be determined as appropriate. Further, instead of providing the notch 41 in the patch part 40, circularly polarized waves may be transmitted and received by a system (so-called two-point power supply system) in which the feeding points P4 are provided at two locations.

  The ground element 50 is a linear conductor element formed in an L shape so as to face the first outer edge portion 21 and the second outer edge portion 22 with a predetermined distance D on the upper surface of the substrate 10. In other words, the ground element 50 is a linear conductor in which a linear conductor element formed so as to be parallel to the X axis and a linear conductor element formed so as to be parallel to the Y axis are connected. It is an element. For convenience, a portion facing the first outer edge portion 21 is referred to as a first element portion 51, and a portion facing the second outer edge portion 22 is referred to as a second element portion 52.

  The first element part 51 and the second element part 52 are each formed to have a length corresponding to a quarter of the target wavelength. That is, the entire length of the ground element 50 is formed to be electrically half the target wavelength (that is, half).

  The interval D only needs to be sufficiently small with respect to the effective length of the target wavelength, and a specific value may be appropriately determined by a simulation or a test (hereinafter, a test or the like). In the present embodiment, as an example, the length is equivalent to 1/50 of the target wavelength. The width of the ground element 50 itself is also required to be sufficiently small with respect to the effective length of the target wavelength, and the specific value may be designed as appropriate.

  If the distance D between the earth element 50 and the main ground portion 20 is too large with respect to the target wavelength, the earth element 50 excites as an independent antenna element, and the characteristics (directivity and gain) of the antenna device 1 as a whole are obtained. It will be disturbed. Therefore, the interval D is preferably set to 1/50 or less of the target wavelength.

  The bridge portion 60 is a conductive member that connects the ground element 50 and the main ground portion 20. The bridge part 60 is formed so as to connect the element center part 53 located at the center of the earth element 50 and the first corner part of the main ground part 20. The first corner portion of the main ground portion 20 is a portion where the first outer edge portion 21 and the second outer edge portion 22 are connected. The center of the ground element 50 refers to a portion located in the middle from one end to the other end.

  The coaxial cable 200 is attached to the main body portion 100 configured as described above so as to cross the ground element 50 and the external conductor 220 is capacitively coupled to the ground element 50. Here, it is assumed that the coaxial cable 200 is attached so that a protective coating (so-called sheath) of the coaxial cable 200 is in close contact with the bottom surface of the main body 100. The bottom surface of the main body portion 100 is a surface including the lower surface of the substrate 10 and the sub-ground portion 20A.

  The locking of the coaxial cable 200 to the main body 100 may be realized by soldering or caulking. The aforementioned external conductor connection portion 80 also contributes to lock the coaxial cable 200 to the main body portion 100. Moreover, you may latch the coaxial cable 200 with respect to the main-body part 100 using metal fittings. The drawing position of the coaxial cable 200 with respect to the main body 100 is fixed by various methods.

  In the present embodiment, as an example, the coaxial cable 200 is attached to the bottom surface of the main body portion 100 so as to pass below the midpoint P5 of the second element portion 52. The midpoint P5 corresponds to a point where the coaxial cable 200 and the earth element 50 intersect in plan view (hereinafter, an intersection). Since the distance from the element central part 53 to the middle point P5 corresponds to one quarter of the entire length, the distance from the element central part 53 to the middle point P5 electrically corresponds to one eighth of the target wavelength. That is, the coaxial cable 200 according to the present embodiment is configured so that the main body portion intersects the earth element 50 at a position electrically separated from the element central portion 53 of the earth element 50 by a distance corresponding to one-eighth of the target wavelength. 100 is attached.

  In the present embodiment, as an example, a mode in which the coaxial cable 200 is attached to the main body 100 so that the intersection is the midpoint P5 of the second element portion 52 is disclosed, but the present invention is not limited thereto. For example, the intersection may be displaced from the midpoint P5 in the Y-axis direction. The coaxial cable 200 may be attached so as to intersect the first element unit 51.

  Furthermore, the coaxial cable 200 need only be attached so that the ground element 50 and the outer conductor 220 are capacitively coupled, and is not necessarily attached in close contact with the main body 100. A predetermined outer space may be provided between the coaxial cable 200 and the bottom surface of the main body within a range in which the ground element 50 and the outer conductor 220 are capacitively coupled.

  Note that the maximum value of the distance at which the earth element 50 and the external conductor 220 are capacitively coupled is determined according to the frequency of the radio wave to be transmitted / received (that is, the target frequency). The separation value range in which the earth element 50 and the outer conductor 220 can be capacitively coupled may be specified by an actual test, simulation, or the like, and a separation that can obtain a desired degree of coupling in the value range may be employed.

  The coaxial cable 200 may be attached to the upper surface of the substrate 10. In that case, a feeding point and a grounding point are formed by the strip line. Further, when the external conductor 220 and the sub-ground portion 20 </ b> A are connected using a strip line, the strip line is formed so as to intersect with the ground element 50.

<Operation of antenna device 1>
Next, the operation and effect of the antenna device 1 of the present embodiment will be described using a general patch antenna (in other words, the ground element 50 is not provided) as a comparative configuration. The operation when the antenna device 1 radiates radio waves and the operation when the antenna devices 1 receive radio waves are reversible. Therefore, the operation when radiating radio waves will be described here, and the description of the operation when receiving radio waves will be omitted.

  Generally, when a radiated current flows through the patch portion of the patch antenna, an image current in the direction opposite to the radiated current is generated at the ground portion. FIG. 5 is a diagram showing a current distribution during radio wave emission in the comparative configuration.

  For convenience, in FIG. 5, the members corresponding to the members included in the antenna device 1 according to the present embodiment are also given the same reference numerals for the comparative configuration. A solid line arrow in the drawing represents a current (that is, a radiation current) flowing through the patch unit 40, and a broken line arrow represents a current (that is, an image current) induced in the main ground unit 20 by the radiation current.

  In such a comparative configuration, when the area of the main ground portion 20 is relatively small, the image current leaks to the outer conductor 220 of the coaxial cable 200. When the image current leaks to the external conductor 220, radio waves are emitted from the coaxial cable 200, and the directivity is disturbed.

  The antenna device 1 of the present embodiment also operates as a well-known patch antenna by the main ground unit 20, the sub ground unit 20A, and the patch unit 40. Therefore, when a radiation current flows through the patch unit 40, an image current in the opposite direction to the radiation current is generated in the main ground unit 20.

  However, in the present embodiment, the earth element 50 is provided along the outer periphery of the main ground portion 20. Since the earth element 50 is electrically formed to have a length corresponding to a half wavelength of the target wavelength, the image current generated in the main ground part 20 easily flows into the earth element 50 through the bridge part 60. . This is because the ground element 50 behaves smaller in impedance than the coaxial cable 200 for the image current generated in the main ground portion 20.

  Further, the coaxial cable 200 is arranged in a positional relationship in which the outer conductor 220 is capacitively coupled to the ground element 50. Further, as viewed from the portion of the external conductor 220 that is capacitively coupled to the ground element (hereinafter referred to as capacitive coupling portion), it is connected to the main body portion 100 including the main ground portion 20 rather than the side connected to the wireless communication device. The input impedance is smaller on the other side. Therefore, the image current flowing into the earth element 50 returns from the ground point to the sub-ground portion 20A through the external conductor 220 and further returns to the main ground portion 20.

  Further, in the region near the second outer edge portion 22 of the main ground portion 20, the traveling direction of the image current is a direction that flows into the ground element 50. That is, in the region near the second outer edge portion 22, an image current flows in a direction opposite to the current flowing through the second element portion 52 of the ground element 50. As a result, as shown in FIG. 6, a loop-shaped current path is formed that passes through the bridge portion 60, the second element portion 52 of the ground element 50, the external conductor 220, and the second outer edge portion 22 of the main ground portion 20. The

  As the image current generated in the main ground portion 20 flows back through the above-described current path, the image current is attenuated as heat. As a result, the leakage current from the main body 100 to the outer conductor 220 of the coaxial cable 200 is reduced.

  It should be noted that the ground connection point realized by the ground bridge portion 70 only needs to be disposed in a region closer to the second outer edge portion 22 than the center of the main ground portion 20. However, it is more preferable that the ground connection point is provided in the vicinity of the second outer edge portion 22. For example, the ground connection point is preferably provided in a region that is electrically within 1/20 of the target wavelength from the second outer edge portion 22 in the Y-axis direction. According to such an aspect, the image current flowing through the main ground portion 20 can be concentrated on the second outer edge portion 22, and the above-described effects can be enhanced.

  FIG. 7 is a diagram showing the directivity of the antenna device 1 of the present embodiment and the directivity of the comparison configuration obtained by a test such as simulation. The solid line in FIG. 7 represents the directivity of the antenna device 1 of the present embodiment, and the broken line represents the directivity of the comparative configuration. Each configuration is designed so that the gain in the 0 ° direction is maximized with the coaxial cable removed. The 0 ° direction corresponds to the positive direction of the Z axis.

  As shown in FIG. 7, in the comparative configuration, the direction in which the radiation gain is maximized (hereinafter, the maximum radiation direction) due to the leakage current flowing in the outer conductor 220 of the coaxial cable 200 is the direction in which the coaxial cable 200 is drawn. Inclined in the direction of °. Although illustration is omitted, it has been confirmed by tests and the like that the maximum radiation direction is inclined in the 90 ° direction as the coaxial cable 200 becomes longer. On the other hand, according to the configuration of the present embodiment, as indicated by the solid line in FIG. 7, the maximum radiation direction can be maintained in the 0 ° direction.

  FIG. 8 is a diagram showing the result of measuring the intensity distribution of the leakage current flowing on the outer conductor 220 of the coaxial cable 200 in each of the present embodiment and the comparative configuration. The vertical axis represents the distance from the connection point between the external conductor 220 and the subground portion 20A, and the vertical axis represents the current amplitude. The current amplitude is normalized by the current value at the feeding point. A solid line represents the characteristic of the present embodiment, and a broken line represents the characteristic of the comparative configuration.

  From the results shown in FIG. 8, it can be seen that according to the present embodiment, leakage of current to the outer conductor 220 of the coaxial cable 200 can be suppressed. In particular, in the region where the distance from the connection point is 80 mm or more, it can be seen that about 40 dB can be suppressed as compared with the comparative configuration.

  Further, in the above configuration, a balun such as a super top is not necessary to obtain the above effect. Therefore, the enlargement of the whole apparatus accompanying introducing a balun can be suppressed. That is, according to the above configuration, both the size reduction of the antenna device 1 and the suppression of the leakage current to the outer conductor 220 of the coaxial cable 200 can be achieved. In addition, an increase in manufacturing cost associated with the introduction of the balun can be avoided.

  The antenna device 1 described above can be used as, for example, a GNSS receiver that receives radio waves transmitted from a positioning satellite used in GNSS (Global Navigation Satellite System). Moreover, the antenna device 1 described above may be used for transmitting and receiving radio waves in a frequency band used in a road usage fee billing system. The road usage fee billing system is a system that performs payment processing of toll road usage fees by wireless communication between a wireless communication device mounted on a vehicle and a communication device provided at the entrance and exit of a toll road. is there. As a road use fee billing system, for example, an ETC (Electronic Toll Collection: registered trademark) system is known.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, The various modifications described below are also contained in the technical scope of this invention, and also in addition to the following However, various modifications can be made without departing from the scope of the invention.

  In addition, about the member which has the same function as the member described in the above-mentioned embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted. In addition, when only a part of the configuration is mentioned, the configuration of the above-described embodiment can be applied to the other portions.

[Modification 1]
Although the aspect which made the object frequency 1.575 GHz was illustrated above, arbitrary frequencies, such as 5.8 GHz, 2.4 GHz, and 700 MHz, can be employ | adopted for an object frequency. Furthermore, although the configuration for transmitting and receiving circularly polarized waves has been disclosed above, the configuration is not limited thereto. It is good also as a structure which transmits / receives linearly polarized waves, such as horizontal polarization and vertical polarization.

[Modification 2]
In the above-described embodiment, the aspect in which the coaxial cable 200 is attached to the main body 100 such that the coaxial cable 200 and the ground element 50 intersect below or above the middle point P5 of the second element portion 52 has been disclosed. Not limited to this.

  The point where the coaxial cable 200 and the earth element 50 intersect (that is, the intersection) in a plan view is preferably located at a position away from the connection portion (that is, the element center portion 53) between the bridge portion 60 and the earth element 50. As the intersection is located farther from the element central portion 53, the path length through which the image current circulates becomes longer as shown in FIG. 9, and the effect of converting the image current into heat increases. In other words, the effect of suppressing the leakage current to the outer conductor 220 of the coaxial cable 200 can be enhanced.

  FIG. 9 shows a mode in which the ground bridge portion 70 and the external conductor connection portion 80 are provided at positions that overlap in a plan view. The power supply to the patch unit 40 may be realized by a microstrip line (not shown) extending from the internal conductor 210.

[Modification 3]
In the above-described embodiment, the conductor pattern (that is, the sub-ground portion) that provides the ground potential is also provided on the lower surface of the substrate 10. However, the embodiment is not limited thereto. As illustrated in FIG. 10, a mode in which only the main ground portion 20 is provided as a conductor pattern for providing a ground potential without using the sub-ground portion 20 </ b> A may be employed. In that case, the connection point between the main ground portion 20 and the external conductor 220 corresponds to the ground connection point described in the claims.

[Modification 4]
In the above-described embodiment, the aspect in which the main body 100 is configured to operate as a patch antenna is illustrated, but the present invention is not limited thereto. In other words, the radiating element may not be a flat member.

  For example, as shown in FIG. 11, the radiating element included in the main body 100 may be a linear conductor element 91 provided so as to stand on the main ground portion 20. That is, the main body 100 may be configured to operate as a monopole antenna. Further, the radiating element included in the main body 100 may be a linear conductor element 92 provided on the substrate 10 as shown in FIG.

[Modification 5]
In the above-described embodiment, the ground element 50 is illustrated in an L shape, but the present invention is not limited to this. The earth element 50 may be formed so as to have a length electrically corresponding to a half wavelength of the target wavelength along the outer edge portion of the main ground portion 20. Therefore, the earth element 50 may be arranged in a U-shape (in other words, a square bracket shape) as shown in FIG.

  Further, the shape of the ground element 50 may be determined according to the planar shape of the main ground portion 20. If the main ground portion 20 is circular as shown in FIG. 14, the ground element 50 has an arc shape. What is necessary is just to form. In any aspect, the ground element 50 is electrically connected to the main ground portion 20 at the center thereof.

  As described above, various shapes such as a rectangle, a polygon such as a pentagon and a hexagon, a circle, and an ellipse can be adopted as the planar shape of the main ground portion 20. Moreover, the shape which provided the notch part in one part of those figures, or rounded the corner | angular part is also employable. In FIG. 13 and FIG. 14, illustration of the patch portion 40, the coaxial cable 200, and the like is omitted.

[Modification 6]
Further, the ground element 50 may be shortened in overall physical length by inserting a coil 54 as shown in FIG. 15, for example. The inductance that the coil 54 should have may be designed as appropriate. In FIG. 15, illustration of the patch unit 40, the coaxial cable 200, and the like is omitted.

100 Main body portion (antenna main body portion), 200 Coaxial cable, 10 Substrate, 20 Main ground portion (ground portion), 20A Sub-ground portion, 21 First outer edge portion (earth facing edge portion), 22 Second outer edge portion (earth facing) Edge part), 30 support part, 40 patch part, 50 ground element, 51 first element part, 52 second element part, 53 element central part, 60 bridge part, 70 ground bridge part, 80 external conductor connection part, 91. 92 Conductor element (radiating element)

Claims (3)

An antenna device comprising: an antenna main body (100) for transmitting and receiving radio waves of a predetermined frequency; and a coaxial cable (200) connected to the antenna main body,
The antenna body is
A ground connection point electrically connected to the outer conductor of the coaxial cable, and a ground part (20) which is a flat conductor member;
A radiating element (40, 91, 92) electrically connected to the inner conductor of the coaxial cable;
A grounding element (50), which is a linear conductor element arranged to face the outer edge of the ground part with a predetermined interval,
The earth element is formed to have a length corresponding to one half of the target wavelength which is the wavelength of the radio wave to be electrically transmitted and received,
The grounding element is electrically connected to the outer edge of the ground part at the center thereof,
The antenna device, wherein the coaxial cable is attached to the antenna main body so that the coaxial cable intersects with the ground element in a plan view and the outer conductor is capacitively coupled to the ground element. In claim 1,
The coaxial cable is attached to the antenna main body so as to intersect the ground element at a position that is electrically separated from the center of the ground element by a distance equivalent to one-eighth of the target wavelength. An antenna device characterized by the above. In claim 1 or 2,
Before Kigu land connection point, the center of the ground portion, the antenna device, characterized in that the grounding element is provided in a region to be a side that is provided.

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