JP6979599B2 - Antenna device - Google Patents

Description

The present invention relates to an antenna technique, and more particularly to an antenna device in which a feeding element is arranged on a dielectric substrate.

An example of miniaturizing an antenna is a microstrip antenna. In order to change the directivity of the microstrip antenna, a plurality of non-feeding elements are arranged around each side of the substantially rectangular microstrip antenna, and the electric length of each non-feeding element is switched (see, for example, Patent Document 1). ).

Japanese Unexamined Patent Publication No. 2012-120150

If the distance between the microstrip antenna and the non-feeding element is wide, the gain improvement effect is small even if the non-feeding element is arranged.

The present invention has been made in view of these circumstances, and an object of the present invention is to provide a technique for improving antenna characteristics.

In order to solve the above problems, the antenna device of an embodiment of the present invention is arranged on the first surface, a dielectric substrate having a second surface opposite to the first surface, and a planar shape. One ground element, a feeding element arranged so that at least a part thereof faces the one ground element with the dielectric substrate interposed therebetween, and at least one on the second surface. A first non-feeding element whose portion faces the one ground element with the dielectric substrate interposed therebetween and is arranged apart from the feeding element, and at least a part of the dielectric substrate on the second surface. A second non-feeding element which faces the one ground element and is arranged apart from the feeding element, and at least a part of the second surface sandwiching the dielectric substrate. A third non-feeding element facing the ground element and spaced away from the feeding element, and at least a part of the second surface facing the one ground element with the dielectric substrate interposed therebetween. A fourth non-feeding element arranged apart from the feeding element, and at least a part of the second surface facing the one ground element with the dielectric substrate interposed therebetween, and the feeding element. With the fifth non-feeding element arranged apart from the first non-feeding element, the second non-feeding element, the third non-feeding element, and the fourth non-feeding element. On the second surface, at least a part thereof faces the one ground element with the dielectric substrate interposed therebetween, and is separated from the feeding element, and the first non-feeding element and the second non-feeding element. An antenna device including at least a sixth non-feeding element arranged apart from any of the feeding element, the third non-feeding element, the fourth non-feeding element, and the fifth non-feeding element. At least one of the two outer edge portions intersecting in the feeding element faces the one ground element with the dielectric substrate interposed therebetween, and at least one of the two outer edge portions intersecting in the feeding element. The length of the feeding element in one direction is shorter than half the length of the dielectric at the resonance frequency of the antenna device, and the first outer edge portion of the first non-feeding element facing the feeding element is The length of the first outer edge portion of the first non-feeding element is shorter than the length of the feeding element while facing the one ground element with the dielectric substrate interposed therebetween, and the second non-feeding element is used. In the element, to the power feeding element The second outer edge portion on the opposite side faces the one ground element with the dielectric substrate interposed therebetween, and the length of the second outer edge portion of the second non-feeding element is the length of the feeding element. The third outer edge portion of the third non-feeding element, which is shorter than the length and faces the feeding element, faces the one ground element with the dielectric substrate interposed therebetween, and the third non-feeding element. The length of the third outer edge portion of the above is shorter than the length of the feeding element, and the fourth outer edge portion of the fourth non-feeding element facing the feeding element sandwiches the dielectric substrate. While facing one ground element, the length of the fourth outer edge portion of the fourth non-feeding element is shorter than the length of the feeding element, and the feeding element is the fifth non-feeding element and the said. Located between the sixth non-feeding elements, the feeding element has a shape having at least a first angle and a second angle facing the first angle in a plan view, and is at least one of the fifth non-feeding elements. The portion was arranged so as to surround the first corner of the feeding element, and at least a part of the sixth non-feeding element was arranged so as to surround the second corner of the feeding element.

According to the present invention, the antenna characteristics can be improved.

1 (a)-(b) are plan views showing the structure of the antenna according to the embodiment of the present invention. It is sectional drawing which shows the structure of the antenna of FIG. 1 (a)-(b). 3 (a)-(b) are diagrams showing changes in relative gain with respect to the diameter of the hole portion of FIG. 1 (a). It is a figure which shows the change of the relative gain with respect to the movement distance of the hole portion of FIG. 1 (a). It is a figure which shows the structural example of the circuit part of FIG. 1 (a). 6 (a)-(f) are diagrams showing the effect of the shape of the non-feeding element of FIG. 1 (a). 7 (a)-(c) are diagrams showing the effect of the arrangement of the non-feeding element of FIG. 1 (a). It is a figure which shows the effect by the size of the non-feeding element of FIG. 1 (a). 9 (a)-(f) are diagrams showing the effect of the arrangement and size of the non-feeding element of FIG. 1 (a). 10 (a)-(e) are diagrams showing another effect depending on the size of the non-feeding element of FIG. 1 (a). 11 (a)-(d) is a perspective view showing another structure of the antenna of FIGS. 1 (a)-(b). 12 (a)-(b) are perspective views showing another structure of the antenna of FIG. 1 (a). It is a figure which shows the effect by the arrangement of a feeding point and a slit of FIG. 1 (a).

An outline of the present embodiment will be described before the embodiment of the present invention is specifically described. An embodiment relates to an antenna in which a feeding element is arranged on the front surface of a dielectric substrate and a ground element is arranged on the back surface. An example of an antenna is a microstrip antenna used in an ETC (Electronic Toll Collection System) on-board unit, and its resonance frequency is in the 5.8 GHz band. As described above, the present embodiment aims to improve the antenna characteristics (antenna gain, antenna efficiency), but specifically, it will be described by at least one of the following (1) to (3).

(1) The antenna is provided with a notification circuit for notifying the ETC on-board unit that the antenna is connected to the ETC on-board unit. When a notification circuit is installed near the microstrip line connecting the feeding element and the feeding point, the input impedance starting from the feeding point is affected, so that the mismatch loss increases and the antenna gain decreases. If the notification circuit is arranged around the outer edge of the feeding element that is the radiation source in this way, the antenna characteristics deteriorate. In this embodiment, a hole is provided near the central portion of the feeding element, and the notification circuit is arranged so as to be surrounded by the feeding element. As a result, the influence on the input impedance is reduced, and the antenna characteristics are improved.

(2) When a plurality of non-feeding elements, which are parasitic elements, are arranged around the feeding element, if the distance between the feeding element and the non-feeding element is wide, the effect of improving the antenna gain is small. The intervals should be narrowed to some extent. However, if the interval is narrowed, the non-feeding element also resonates at the resonance frequency, so that the effective resonance frequency is lowered by the electromagnetic coupling between the non-feeding element and the feeding element. As a result, the antenna gain at the desired resonance frequency is reduced. In this embodiment, the size of the feeding element is determined so that the resonance frequency of the feeding element is higher than the desired resonance frequency. A plurality of non-feeding elements are arranged while the distance from such feeding elements is narrowed to some extent. As a result, the effective resonance frequency is near the desired band, and the antenna gain at the desired resonance frequency is improved.

(3) The feeding element is generally arranged so as to overlap the central portion of the ground element. This is because the radio waves radiated from the feeding element are diffracted from the end of the ground element at an equal distance to form antenna directivity in the zenith direction. In consideration of this, it is preferable that the dielectric substrate has a substantially square shape. On the other hand, when an electric circuit other than the power feeding element is mounted on the surface of the dielectric substrate, the dielectric substrate has a substantially rectangular shape instead of a substantially square shape. When the ground element is also formed into a substantially rectangular shape according to the mounting portion of the electric circuit, the distance from the antenna element to the ground element becomes non-uniform, and a component that cancels the phase is generated, so that the above-mentioned directivity pattern is broken. , The antenna gain in the zenith direction is reduced. In this embodiment, the ground potential is separated into the first ground element and the second ground element by forming a slit in the ground element. Further, the first ground element has a substantially square shape, and the feeding element is overlapped with the central portion thereof. Further, the feeding point is arranged on the slit side. As a result, the current flowing in the longitudinal direction of the dielectric substrate is reduced, so that the above-mentioned directivity pattern is less likely to collapse.

In the following description, "parallel" and "orthogonal" include not only perfectly parallel and orthogonal, but also cases where they deviate from parallel within the range of error. In addition, "abbreviation" means that they are the same in an approximate range.

1 (a)-(b) are plan views showing the structure of the antenna 100 according to the embodiment of the present invention. FIG. 2 is a cross-sectional view showing the structure of the antenna 100. As shown in FIGS. 1 (a)-(b) and 2, an orthogonal coordinate system including an x-axis, a y-axis, and a z-axis is defined. The x-axis and y-axis are orthogonal to each other in the plane of the antenna 100. The z-axis is perpendicular to the x-axis and the y-axis. The positive directions of the x-axis, y-axis, and z-axis are defined by the directions of the arrows in FIGS. 1 (a)-(b) and 2, and the negative directions are the directions opposite to the arrows. It is stipulated. Of the two main surfaces forming the antenna 100 and parallel to the xy plane, the main plane arranged on the positive side of the z-axis is the surface 12, which is negative on the z-axis. The main plane arranged on the directional side is the back surface 14. When the back surface 14 is called the first surface, the front surface 12 is called the second surface.

The antenna 100 includes a dielectric substrate 10, a first ground element 20a collectively referred to as a ground element 20, a second ground element 20b, a slit 22, a feeding element 30, a hole portion 32, a land portion 34, a circuit portion 36, and a microstrip line. 38, feeding point 40, electric circuit unit 42, first non-feeding element 50a, second non-feeding element 50b, third non-feeding element 50c, fourth non-feeding element 50d, fifth non-feeding element 50. The feeding element 50e and the sixth non-feeding element 50f are included. The number of non-feeding elements 50 is not limited to "6".

The dielectric substrate 10 is formed in a plate shape, and has a rectangular front surface 12 and a back surface 14 that are longer in the x-axis direction than the y-axis direction. On the back surface 14 of the antenna 100, the first ground element 20a is arranged on the positive direction side of the x-axis, and the first ground element 20a has a substantially square shape. Further, on the back surface 14 of the antenna 100, the second ground element 20b is arranged on the negative direction side of the x-axis. Here, a slit 22 is arranged between the first ground element 20a and the second ground element 20b. The slit 22 is formed in the ground element 20, and the back surface 14 of the dielectric substrate 10 is exposed in the slit 22. In this way, the ground potential of the second ground element 20b is separated from the first ground element 20a with the slit 22 as a boundary.

On the surface 12 of the dielectric substrate 10, the portion overlapping with the first ground element 20a is defined as the first region 24, and the portion overlapping with the second ground element 20b is defined as the second region 26. The 24 and the second region 26 are also separated from each other with the slit 22 as a boundary. On the surface 12 of the dielectric substrate 10, a feeding element 30 having a substantially square shape is arranged near the central portion of the first region 24. Therefore, the feeding element 30 is arranged overlapping with the first ground element 20a on the projection surface (hereinafter, simply referred to as “projection surface”) parallel to the front surface 12 or the back surface 14. The feeding element 30 may be called a microstrip antenna or a patch antenna.

A hole portion 32 is arranged near the central portion inside the feeding element 30, and a land portion 34 is arranged near the central portion inside the hole portion 32. The land portion 34 is a conductor having a cylindrical shape, and its height in the z-axis direction is close to the thickness of the feeding element 30. Further, since the hole portion 32 is surrounded by the feeding element 30 in an arc shape, the hole portion 32 is opened in a donut shape. The shapes of the hole portion 32 and the land portion 34 are not limited to these. A through-hole portion 46 formed by a conductor is arranged so as to penetrate the dielectric substrate 10 from the surface on the negative side of the z-axis of the land portion 34 to the surface on the positive direction side of the z-axis of the first ground element 20a. The through-hole portion 46 electrically connects the first ground element 20a and the land portion 34.

A circuit unit 36 is arranged between the power feeding element 30 and the land unit 34. The configuration of the circuit unit 36 may be arbitrary, but for example, when the circuit unit 36 is a notification circuit, the resistance element corresponds to the circuit unit 36. The circuit unit 36 may be a semiconductor element, reactance, or the like. The feeding element 30 and the land portion 34 are electrically connected by such a circuit portion 36. Further, on the surface 12 of the dielectric substrate 10, a plurality of non-feeding elements 50 are arranged around the feeding element 30. The shape of each non-feeding element 50 does not have to be the same.

The microstrip line 38 connected to the outer edge of the feeding element 30 on the negative side of the x-axis extends in the direction of the slit 22. A feeding point 40 is arranged at the slit 22 side end of the microstrip line 38. Therefore, the feeding point 40 is connected to the feeding element 30 via the microstrip line 38 and is arranged on the slit 22 side with respect to the feeding element 30. One end of the coaxial cable 44 is connected to the feeding point 40. The other end of the coaxial cable 44 is connected to, for example, an ETC on-board unit (not shown). With such a configuration, the feeding element 30 is fed from the feeding point 40, and the antenna 100 transmits / receives the ETC signal and inputs / outputs the signal to the ETC on-board unit via the coaxial cable 44.

An electric circuit portion 42 having a substantially rectangular shape is arranged in the second region 26 on the surface 12 of the dielectric substrate 10. Therefore, the electric circuit unit 42 is arranged so as to overlap the second ground element 20b on the projection surface. Any circuit can be used as the electric circuit unit 42. For the sake of clarity, the structure in which the second region 26 is omitted may also be referred to as an antenna 100.

So far, the basic structure of the antenna 100 has been described. Hereinafter, the structure of the antenna 100 will be described in more detail. In particular, here, (1) the arrangement of the circuit unit 36, (2) the shape and arrangement of the feeding element 30 and the non-feeding element 50, and (3) the structure including the second region 26 will be described in this order. The characteristics shown below are the results of the simulation.

(1) Arrangement of Circuit Unit 36 First, the diameter of the hole portion 32 when the circuit unit 36 is arranged will be described. 3 (a)-(b) show the change of the relative gain with respect to the diameter of the hole 32. FIG. 3A shows a change in the relative gain when the diameter of the hole portion 32 arranged at the center of the feeding element 30 of FIG. 1A is changed. The center of the feeding element 30 is a position connecting the midpoint in the x-axis direction and the midpoint in the y-axis direction of the feeding element 30. Here, the horizontal axis indicates the hole diameter, and the vertical axis indicates the relative gain. As shown in the figure, when the hole diameter is larger than 3 mm, the relative gain decreases. FIG. 3B shows the relationship between the wavelength and the length when the desired resonance frequency is set to the 5.8 GHz band. With reference to this, based on FIG. 3A, the diameter of the hole portion 32 is set to a length of 1/8 or less of the wavelength at the resonance frequency of the antenna 100.

Next, the position of the hole portion 32 when the circuit portion 36 is arranged will be described. FIG. 4 shows the change in the relative gain with respect to the moving distance of the hole portion 32. This can be said to be a change in the relative gain with respect to the moving distance of the circuit unit 36. Here, from the center of the feeding element 30 in FIG. 1A, the positive direction of the x-axis (+ x-axis direction 200), the negative direction of the y-axis (−y-axis direction 202), and the positive direction of the y-axis (+ y-axis direction 204). ), The change in the relative gain when the hole portion 32 is moved in the negative direction of the x-axis (−x-axis direction 206) is shown. The relative gain is shown with reference to the case where the hole portion 32 is arranged at the center of the feeding element 30. When the hole portion 32 or the circuit portion 36 is deviated from the center, the relative gain tends to decrease. Therefore, the hole portion 32 is formed within a moving distance of about 1.2 mm from the center of the feeding element 30, that is, a length of up to 1/20 of the wavelength at the resonance frequency of the antenna 100.

Further, the structure when the resistance element, the semiconductor element, the reactance and the like are not used as the circuit unit 36 will be described. FIG. 5 shows a structural example of the circuit unit 36, and shows a top view of the surface 12. The circuit portion 36 is formed as a stub pattern extending from the feeding element 30 on the hole portion 32, and continues to the land portion 34. The circuit unit 36 of such a stub pattern has a high impedance in a desired frequency band due to the inductive reactance component. As described above, it is preferable that the impedance of the circuit unit 36 is high.

(2) Shape and arrangement of the feeding element 30 and the non-feeding element 50 FIGS. 6A-(f) show the effect of the shape of the non-feeding element 50. 6 (a)-(c) are top views showing the structure of the conventional antenna 170 to be compared with the antenna 100. In these antennas 170, the portion of the second region 26 in FIG. 1A is omitted. In the antenna 170 of FIG. 6A, the feeding element 130 is arranged in the central portion of the dielectric substrate 110. Here, the dielectric substrate 110 and the feeding element 130 correspond to the dielectric substrate 10 and the feeding element 30. In the feeding element 130, the outer edge portion in the x-axis direction and the outer edge portion in the y-axis direction intersect, and the length of at least one of them is set to ½ of the wavelength λ at the resonance frequency of the antenna 170. To.

In the antenna 170 of FIG. 6B, in addition to the structure of FIG. 6A, the first non-feeding element 150a to the eighth non-feeding element 150h collectively referred to as the non-feeding element 150 are arranged around the feeding element 130. Will be done. Here, the non-feeding element 150 is formed in a rod shape so that the outer edge portion facing the feeding element 130 becomes long. The diode arranged between the adjacent non-feeding elements 150 is electrically isolated, and the distance between the feeding element 130 and the non-feeding element 150 is about 1 / of the wavelength λ at the resonance frequency of the antenna 170. The length is 4. In the antenna 170 of FIG. 6 (c), the distance between the feeding element 130 and the non-feeding element 150 in FIG. 6 (b) is set to be about 1/20 of the wavelength λ at the resonance frequency of the antenna 170. .. That is, in FIG. 6 (c), the distance between the feeding element 130 and the non-feeding element 150 is narrower than that in FIG. 6 (b).

In FIG. 6 (d), the antenna 100 of FIG. 1 (a) is shown deformed in order to facilitate comparison with FIG. 6 (c). Here, the first non-feeding element 50a to the eighth non-feeding element 50h, which are collectively referred to as the non-feeding element 50, are arranged around the feeding element 30. Further, in the feeding element 30, the outer edge portion in the x-axis direction and the outer edge portion in the y-axis direction intersect, and at least one length thereof, that is, at least one length in the x-axis direction and the y-axis direction is set. It is shorter than half the length of the wavelength λ at the resonance frequency of the antenna 100. That is, in the x-axis direction or the y-axis direction, the length of the feeding element 30 is shorter than the length of the feeding element 130. Further, in each non-feeding element 50, the length of the outer edge portion on the side facing the feeding element 30 is shorter than the length of the feeding element 30 in the same direction as the outer edge portion. For example, the length of the first passive element 50a in the x-axis direction is shorter than ½ of the length of the feeding element 30 in the x-axis direction. The distance between the feeding element 30 and the non-feeding element 50 is set to a length of about 1/20 of the wavelength λ at the resonance frequency of the antenna 100, as in FIG. 6C.

Hereinafter, for the sake of clarity, each of FIGS. 6A and 6D will be referred to as a structure A, a structure B, a structure C, and a structure D. FIG. 6 (e) shows VSWR (Voltage Standing Wave Ratio) when the frequency is changed. It can be said that the lower the VSWR, the better the characteristics. Further, a band including the resonance frequencies of the antenna 170 and the antenna 100 is shown as a desired band. On the other hand, FIG. 6 (f) shows the antenna gain when the frequency is changed. It can be said that the higher the antenna gain, the better the characteristics. In these, the structure B characteristic 212 becomes substantially the same as the structure A characteristic 210. This is because the distance between the feeding element 130 and the non-feeding element 150 in FIG. 6B is too wide, so that the non-feeding element 150 does not contribute to the improvement of the characteristics.

In the structure C characteristic 214, the antenna gain is improved at a frequency lower than the desired band as compared with the structure A characteristic 210 and the structure B characteristic 212, but the antenna gain is not improved in the desired band. This is because the distance between the feeding element 130 and the non-feeding element 150 is narrow, so that the effective length of the feeding element 130 can be regarded as being equivalently long, which lowers the effective resonance frequency. be.

In the structure D characteristic 216, both VSWR and the antenna gain are improved in the desired band as compared with the structure A characteristic 210 to the structure C characteristic 214. This can be said to improve the antenna gain without changing the radiation pattern in the desired band. Again, since the distance between the feeding element 30 and the non-feeding element 50 is narrow, it can be considered that the effective length of the feeding element 30 is equivalently long. However, since the length of the feeding element 30 is set to have a resonance frequency higher than the desired band, when the non-feeding element 50 is arranged, it resonates in the desired band. As described above, the length of the feeding element 30 in the x-axis direction or the y-axis direction is shorter than the length of 1/2 of the wavelength λ at the resonance frequency of the antenna 100. Further, in each non-feeding element 50, the length of the outer edge portion on the side facing the feeding element 30 is shorter than the length of the feeding element 30 in the same direction as the outer edge portion.

7 (a)-(c) are diagrams showing the effect of the arrangement of the non-feeding element of FIG. 1 (a). In FIG. 7A, the distance between the feeding element 30 and the non-feeding element 50 is set to be about 1/20 of the wavelength λ at the resonance frequency of the antenna 100. Further, in FIG. 7B, the distance between the feeding element 30 and the non-feeding element 50 is set to be about 1/5 of the wavelength λ at the resonance frequency of the antenna 100. Here, this distance will be described. FIG. 7C shows the effect of the arrangement of the non-feeding element 50, the horizontal axis shows the distance in units of the wavelength λ, and the vertical axis shows the antenna for the case where the non-feeding element 50 is not arranged. The amount of gain improvement is shown. In each non-feeding element 50, the length of the outer edge portion on the side facing the feeding element 30 is set to 1/4 of the wavelength λ at the resonance frequency of the antenna 100. The amount of improvement in antenna gain decreases as the distance increases. Therefore, the distance between each of the plurality of non-feeding elements 50 and the feeding element 30 is shorter than 1/10 of the wavelength at the resonance frequency of the antenna 100.

Next, the length of the outer edge portion of the non-feeding element 50 on the non-feeding side of the feeding element 30 will be described. This corresponds to the length of the first non-feeding element 50a in the y-axis direction in FIG. 6D. FIG. 8 shows the effect of the size of the non-feeding element 50, the horizontal axis shows the length in units of wavelength λ, and the vertical axis shows the improvement of the antenna gain when the non-feeding element 50 is not arranged. Indicates the amount. Here, the distance between the feeding element 30 and the non-feeding element 50 is set to 1/50 of the wavelength λ at the resonance frequency of the antenna 100, and the length of the outer edge portion of the non-feeding element 50 on the side facing the feeding element 30. The length is 1/4 of the wavelength λ at the resonance frequency of the antenna 100. Under such circumstances, the amount of improvement in antenna gain increases as the length of the outer edge portion of the non-feeding element 50 on the side opposite to the feeding element 30 increases. Further, when the length is 0.38λ, the amount of improvement in antenna gain is maximized. Further, when the length approaches 1/2 of the wavelength λ, the amount of improvement in antenna gain decreases sharply.

This is because if the length of the non-feeding element 50 on the non-feeding side of the feeding element 30 is about 1/4 of the wavelength λ, the non-feeding element 50 does not resonate in the desired band, and the feeding element 30 is equivalently used. An electric field is concentrated in the vicinity of the feeding element 30 as a part, but if the length becomes about 1/2 of the wavelength λ, the non-feeding element 50 operates as an antenna that resonates in a desired band, so that the feeding element 50 becomes a non-feeding element 50. This is because the electric field is strongly distributed, which affects the current distribution, disturbs the radiation pattern, and affects the impedance of the antenna. In summary, the length of the non-feeding element 50 on the non-feeding side of the feeding element 30 is shorter than the length of at least one feeding element 30 in the x-axis direction and the y-axis direction, and the resonance frequency of the antenna 100. The length is 1/5 or more of the wavelength in.

Next, the arrangement of the non-feeding element 50 will be described. 9 (a)-(f) show another effect depending on the arrangement and size of the non-feeding element 50. 9 (a) corresponds to FIG. 6 (a), FIG. 9 (b) corresponds to FIG. 6 (c), and FIG. 9 (c) corresponds to FIG. 6 (d). In FIGS. 9 (a) and 9 (b), the length of the feeding element 130 in the x-axis direction or the y-axis direction is 1/2 of the wavelength λ at the resonance frequency of the antenna 170, as in FIG. 6 (d). Is shorter than the length of. Here, for the sake of clarity, each of FIGS. 9A and 9C is also referred to as a structure A, a structure C, and a structure D.

In FIG. 9D, the 7th non-feeding element 50g and the 8th non-feeding element 50h are added as compared with FIG. 9C. Specifically, the seventh non-feeding element 50g is arranged so as to be in contact with the corner portion C1 on the positive direction side of the x-axis and the positive direction side of the y-axis of the feeding element 30. Further, the eighth non-feeding element 50h is arranged so as to be in contact with the corner portion C2 on the positive direction side of the x-axis and the negative direction side of the y-axis of the feeding element 30. That is, the second non-feeding element 50b, the seventh non-feeding element 50g, and the third feeding element 30c are arranged so as to surround the corner portion C1 of the feeding element 30, and the fourth non-feeding element 50d and the eighth non-feeding element 50h. The fifth non-feeding element 50e is arranged so as to surround the corner portion C2 of the feeding element 30. As described above, in FIG. 9 (d), the number of non-feeding elements 50 is larger than that in FIG. 9 (c), and the total element area of the non-feeding elements 50 is larger. Here, FIG. 9D is referred to as a structure E.

9 (e) shows the amount of improvement of the antenna gain of the structure C, the structure D, and the structure E with respect to the structure A, and FIG. 9 (f) shows the amount of the efficiency improvement of the structure C, the structure D, and the structure E with respect to the structure A. .. In the structure D, the antenna gain improvement amount and the efficiency improvement amount are larger than those in the structure C. Further, in the structure E, the antenna gain improvement amount is about the same as that in the structure D, but the efficiency improvement amount is large. Therefore, by expanding the element area of the non-feeding element 50, the antenna gain and efficiency are improved.

Next, the size of the non-feeding element 50 will be described. 10 (a)-(e) show another effect depending on the size of the non-feeding element 50. FIG. 10 (a) shows a structure in which the non-feeding element 50 shown in FIG. 9 (e) is close to the shape of the non-feeding element 50 in FIG. 1 (a). As described above, the length of the outer edge portion of the non-feeding element 50 on the side facing the feeding element 30 is shorter than the length of the feeding element 30 in the same direction as the outer edge portion. Therefore, the length of the first non-feeding element 50a and the fifth non-feeding element 50e in the x-axis direction is shorter than the length of the feeding element 30 in the x-axis direction, and the length of the third non-feeding element 50c in the y-axis direction. The length is shorter than the length of the feeding element 30 in the y-axis direction. Here, FIG. 10A is referred to as a structure F.

10 (b) shows the structure of the antenna 170 to be compared with FIG. 10 (a). The length of the outer edge portion of the non-feeding element 150 on the side facing the feeding element 130 is equal to the length of the feeding element 130 in the same direction as the outer edge portion. Therefore, the lengths of the first non-feeding element 150a and the fifth non-feeding element 150e in the x-axis direction are equal to the length of the feeding element 130 in the x-axis direction, and the length of the fifth non-feeding element 150c in the y-axis direction. Is equal to the length of the feeding element 130 in the y-axis direction. Here, FIG. 10B is referred to as a structure G.

FIG. 10 (c) shows VSWR when the frequency is changed with respect to the structure F. The non-feeding element 50 resonates in the vicinity of P1. Since the frequency of P1 is far from the desired band, it does not affect VSWR in the desired band. On the other hand, FIG. 10D shows VSWR when the frequency is changed with respect to the structure G. The resonance caused by the non-feeding element 150 resonates in the vicinity of P2, that is, in the vicinity of the resonance frequency of the feeding element 130. Therefore, the resonance of the non-feeding element 150 deteriorates VSWR in the desired band. FIG. 10E shows the amount of improvement in antenna gain in a desired band with respect to the structure F and the structure G. Here, when the amount of improvement in antenna gain is smaller than 0 dB, it indicates that the characteristics have deteriorated. For the same reason as described above, the antenna gain improvement amount of the structure F is larger than the antenna gain improvement amount of the structure G.

Various modifications of the antenna 100 described so far will be described. 11 (a)-(d) are perspective views showing another structure of the antenna 100. FIG. 11A is a perspective view of the antenna 100 according to the first modification when viewed from the front surface 12, and FIG. 11B is a back surface 14 of the antenna 100 according to the first modification. It is a perspective view when viewed from. The microstrip line 138 is not used for these, and power is supplied from the back surface 14 side by the feeding point 40.

11 (c) is a perspective view when the antenna 100 according to the second modification is viewed from the surface 12, and FIG. 11 (d) shows the antenna 100 according to the third modification on the surface 12. It is a perspective view when viewed from. In these, the first perturbation unit 60a and the second perturbation unit 60b are provided at the diagonally opposed corner portions of the feeding element 30. The first perturbation unit 60a and the second perturbation unit 60b are collectively referred to as the perturbation unit 60, and have a shape in which a corner portion of the feeding element 30 is cut out. The radio wave radiated from the antenna 100 is circularly polarized by the perturbation unit 60. In addition, in FIG. 11C, the microstrip line 38 is arranged, in FIG. 11D, the microstrip line 38 is not used, and power is supplied from the back surface 14 side by the feeding point 40.

12 (a)-(b) are perspective views showing the structure of the antenna 100, specifically, FIG. 12 (a) shows the antenna 100 according to the fourth modification, and FIG. 12 (b). ) Indicates the antenna 100 according to the fifth modification. So far, a plurality of non-feeding elements 50 are singly arranged at least a part around the feeding element 30. On the other hand, in FIGS. 12 (a) and 12 (b), a plurality of non-feeding elements 50 are doubly arranged in at least a part around the feeding element 30. For example, in FIG. 12A, two non-feeding elements 50, a first non-feeding element 50a and a seventh non-feeding element 50g, are arranged side by side from the feeding element 30 in the positive direction of the y-axis. With such a structure, the non-feeding element 50 is arranged near the end of the dielectric substrate 10, and the antenna gain is improved. In addition, in FIG. 12A, the microstrip line 38 is arranged, in FIG. 12B, the microstrip line 38 is not used, and power is supplied from the back surface 14 side by the feeding point 40.

(3) Structure in which the Second Region 26 is Included In the explanation so far, the second region 26 has been omitted from the antenna 100 in FIG. 1 (a). Hereinafter, the structure of the antenna 100 including the second region 26 will be described. FIG. 13 shows the effect of the arrangement of the feeding point 40 and the slit 22. Here, four structures will be described. Structures H to J indicate the structure of the antenna 170 to be compared with the antenna 100. The structure H is an antenna 170 having the same structure as those in FIGS. 6 (a) and 9 (a). The microstrip line 138 extends from the feeding element 130 in the negative direction of the y-axis and connects the feeding point 140 at the end opposite to the feeding element 130 side. Further, in the dielectric substrate 110, the ground element 120 is arranged on the side opposite to the power feeding element 130. Here, the ground element 120, the microstrip line 138, and the feeding point 140 correspond to the ground element 20, the microstrip line 38, and the feeding point 40. As described above, the current distribution of the structure H forms the antenna directivity in the zenith direction.

The dielectric substrate 110 in the structure I has a shape longer in the x-axis direction than in the y-axis direction, like the dielectric substrate 10 in FIG. 1 (a). Further, the ground element 120 also has a long shape in the x-axis direction according to the shape of the dielectric substrate 110. In the current distribution of the structure I, the ground current (A3) in the vicinity of the feeding point 140 flows in the negative direction of the x-axis along the outer edge of the dielectric substrate 110 extending in the x-axis direction (A1, A2). In the radiation of radio waves from A1, A2, and A3 due to the ground current, as described above, the distance from the radiation end of the antenna element to the diffraction end of the ground element becomes non-uniform, so that components that cancel each other out are generated. As a result, the antenna directivity in the zenith direction is lost, and the antenna gain in the zenith direction is reduced.

The dielectric substrate 110 in the structure J has the same shape as the dielectric substrate 110 in the structure I. On the other hand, instead of the ground element 120, the first ground element 120a and the second ground element 120b are arranged, and the ground potential of these is separated by the slit 122. Further, the first ground element 120a side is designated as the first region 124, and the second ground element 120b side is designated as the second region 126. Here, the first ground element 120a, the second ground element 120b, the slit 122, the first region 124, and the second region 126 are the first ground element 20a, the second ground element 20b, the slit 22, the first region 24, and the second region 126. Corresponds to 2 regions 26. In the current distribution of the structure J, the ground flowing in the negative direction of the x-axis along the outer edge of the dielectric substrate 110 extending in the x-axis direction due to the separation of the first ground element 120a and the second ground element 120b by the slit 122. The current (A1, A2) is smaller than that of the structure I. As a result, the components that cancel each other out become smaller, and the collapse of the antenna directivity in the zenith direction is suppressed.

The structure K corresponds to a structure in which the non-feeding element 50 is omitted from the antenna 100 in FIG. 1 (a). The microstrip line 38 extends from the feeding element 30 in the negative direction of the x-axis and connects the feeding point 40 at the end opposite to the feeding element 30 side. In the current distribution of the structure K, the ground current (A4) in the vicinity of the slit 22 increases by arranging the feeding point 40 in the vicinity of the slit 22. However, the ground current (A1, A2) flowing in the negative direction of the x-axis along the outer edge of the dielectric substrate 10 extending in the x-axis direction is smaller than that of the structure J. As a result, the components that cancel each other out become smaller, and the collapse of the antenna directivity in the zenith direction is further suppressed, so that the antenna gain in the zenith direction becomes closer to that in the case of the structure H.

According to this embodiment, since the circuit unit is surrounded by the feeding element, it is possible to suppress the disturbance of the input characteristics and the radiation characteristics even when the circuit unit is arranged. Further, since the disturbance of the input characteristics and the radiation characteristics is suppressed, the antenna characteristics (antenna gain, antenna efficiency) can be improved. Further, since the through hole portion is arranged, the ground element and the land portion can be electrically connected. Further, since the diameter of the hole portion is set to a length of 1/8 or less of the wavelength at the resonance frequency of the present antenna, the influence on the electromagnetic field of the present antenna can be reduced. Further, since the influence of the antenna on the electromagnetic field is reduced, the influence of the hole can be reduced. Further, since the diameter of the hole portion is set to a length of 1/8 or less of the wavelength at the resonance frequency of this antenna, the input characteristics and the radiation characteristics can be maintained high. Moreover, since the input characteristics and the radiation characteristics are maintained high, the influence of the holes can be reduced.

Further, since the impedance of the circuit portion is increased, the feeding element and the ground element can be separated at a high frequency. Further, since the feeding element and the ground element are separated at a high frequency, it is possible to suppress the disturbance of the input characteristics and the radiation characteristics. Further, since the hole is formed within the length range from the center of the feeding element to 1/20 of the wavelength at the resonance frequency of the present antenna, the change in the resonance frequency of the present antenna can be reduced. Further, since the change in the resonance frequency of this antenna is reduced, it is possible to suppress the disturbance of the input characteristics and the radiation characteristics. Further, since the circuit portion is formed as a stub pattern, the number of circuit parts can be reduced while maintaining the antenna characteristics. Moreover, since the number of circuit parts is reduced, the cost can be reduced.

Further, since the length of the feeding element is shorter than the length of 1/2 of the wavelength at the resonance frequency of this antenna and the length of the non-feeding element is shorter than the length of the feeding element, the feeding element and the non-feeding element at the resonance frequency are not fed. Resonance with the element can be suppressed. Further, since the resonance between the feeding element and the non-feeding element at the resonance frequency is suppressed, the antenna characteristics can be improved. Further, since the distance between the non-feeding element and the feeding element is made shorter than 1/10 of the wavelength at the resonance frequency of this antenna, the non-feeding element can be used as a reflector. Further, since the non-feeding element is used as a reflector, the antenna characteristics can be improved. Further, since the length of the outer edge portion of the non-feeding element on the non-feeding side of the feeding element is shorter than the length of the feeding element, resonance between the feeding element and the non-feeding element at the resonance frequency can be suppressed. Further, since the length of the outer edge portion of the non-feeding element on the non-feeding side of the feeding element is 1/5 or more of the wavelength at the resonance frequency of the present antenna, the antenna characteristics can be improved. Further, since the non-feeding element is arranged so as to surround the corner portion of the feeding element, the element area can be increased. In addition, since a perturbation part is added, it is possible to deal with circularly polarized light.

Further, since the slit is formed in the ground element and the feeding element is arranged on the slit side, the ground current can be reduced. Moreover, since the ground current is reduced, the radiation of the components that cancel each other out of phase is reduced. Moreover, since the radiation of the components that cancel each other out is reduced, the antenna characteristics can be improved. Further, since the width of the slit is widened to some extent, the ground current flowing through the second ground element can be reduced. Further, since the ground current flowing through the second ground element is reduced, the antenna characteristics in the zenith direction can be improved. Further, since the ground potential is separated into the first ground element and the second ground element, the ground current that radiates the components that cancel each other is reduced, and the antenna characteristics can be improved. Further, since the electric circuit unit is mounted in the region overlapping with the second ground element, the usage of the antenna can be expanded.

The present invention has been described above based on the examples. This embodiment is an example, and it is understood by those skilled in the art that various modifications are possible in the combination of each of these components, and that such modifications are also within the scope of the present invention.

The outline of one aspect of the present invention is as follows.
(Item 1-1)
Dielectric board and
A ground element arranged on the first surface side of the dielectric substrate and
A feeding element arranged on the second surface side of the dielectric substrate and
A hole arranged inside the power feeding element and
The land portion arranged inside the hole portion and the land portion
A circuit unit arranged between the power feeding element and the land unit,
An antenna characterized by being equipped with.

According to this aspect, since the circuit unit is arranged at a position that does not affect the input impedance, the antenna characteristics can be improved.

(Item 1-2)
The antenna according to item 1-1, further comprising a through-hole portion that penetrates the dielectric substrate and connects the ground element and the land portion. In this case, since the through-hole portion is arranged, the ground element and the land portion can be electrically connected.
(Item 1-3)
The antenna according to item 1-1 or item 1-2, wherein the diameter of the hole portion is one-eighth or less of the wavelength at the resonance frequency of the present antenna. In this case, since the diameter of the hole portion is set to a length of 1/8 or less of the wavelength at the resonance frequency of the present antenna, the influence of the hole portion can be reduced.
(Item 1-4)
Any of items 1-1 to 1-3, wherein the hole portion is formed within a length range from the center of the feeding element to 1/20 of the wavelength at the resonance frequency of the present antenna. The antenna described in Crab. In this case, since the hole is formed within the length range from the center of the feeding element to 1/20 of the wavelength at the resonance frequency of the present antenna, the influence of the hole can be reduced.
(Item 1-5)
The antenna according to any one of items 1-1 to 1-4, wherein the circuit unit is formed as a stub pattern. In this case, since the circuit portion is formed as a stub pattern, the number of circuit components can be reduced.

(Item 2-1)
It ’s an antenna,
Dielectric board and
The feeding element arranged on one side of the dielectric substrate and
A plurality of non-feeding elements arranged around the feeding element are provided.
The length of the feeding element in at least one direction of the two intersecting outer edges of the feeding element is shorter than ½ of the wavelength at the resonance frequency of the antenna.
An antenna characterized in that, in each of the plurality of non-feeding elements, the length of the outer edge portion on the side facing the feeding element is shorter than the length of the feeding element.

According to this aspect, the length of the feeding element is shorter than the length of 1/2 of the wavelength at the resonance frequency of the present antenna, and the length of the non-feeding element is shorter than the length of the feeding element, so that the antenna characteristics can be improved. ..

(Item 2-2)
Item 2. The antenna according to item 2-1, wherein the distance between each of the plurality of non-feeding elements and the feeding element is shorter than 1/10 of the wavelength at the resonance frequency of the present antenna. In this case, since the distance between the non-feeding element and the feeding element is shorter than 1/10 of the wavelength at the resonance frequency of the present antenna, the non-feeding element can be used as a reflector.
(Item 2-3)
Item 2. The item 2-1 or item 2-2, wherein the length of the outer edge portion of each of the plurality of non-feeding elements on the side non-facing the feeding element is shorter than the length of the feeding element. Antenna. In this case, since the length of the outer edge portion of the non-feeding element on the non-feeding side facing the feeding element is shorter than the length of the feeding element, the antenna characteristics can be improved.
(Item 2-4)
Item 2 characterized in that, in each of the plurality of non-feeding elements, the length of the outer edge portion on the side non-opposing to the feeding element is 1/5 or more of the wavelength at the resonance frequency of the present antenna. The antenna according to -3. In this case, since the length of the outer edge portion of the non-feeding element on the non-feeding side of the feeding element is 1/5 or more of the wavelength at the resonance frequency of the present antenna, the antenna characteristics can be improved.
(Item 2-5)
The antenna according to any one of items 2-1 to 2-4, wherein the non-feeding element is arranged so as to surround a corner portion of the feeding element. In this case, since the non-feeding element is arranged so as to surround the corner portion of the feeding element, the element area can be increased.

(Item 3-1)
Dielectric board and
A ground element arranged on the first surface side of the dielectric substrate and
The slit formed in the ground element and
A feeding element arranged on the second surface side of the dielectric substrate and
It has a feeding point connected to the feeding element, and has a feeding point.
The antenna is characterized in that the feeding point is arranged on the slit side with respect to the feeding element.

According to this aspect, since the slit is formed in the ground element and the feeding element is arranged on the slit side, the ground current that radiates the components whose phases cancel each other is reduced, and the antenna characteristics can be improved.

(Item 3-2)
The ground element is
With the first ground element
A second ground element in which the ground potential is separated from the first ground element is provided with the slit as a boundary.
Item 3. The antenna according to item 3-1, wherein the first ground element is arranged overlapping with the feeding element on the first surface or a projection surface parallel to the second surface. In this case, since the ground potential is separated into the first ground element and the second ground element, the ground current that radiates the canceling components is reduced, and the antenna characteristics can be improved.
(Item 3-3)
Further, an electric circuit portion formed on the second surface side of the dielectric substrate is provided.
The antenna according to item 3-2, wherein the electric circuit unit is arranged overlapping with the second ground element on the first surface or a projection surface parallel to the second surface. In this case, since the electric circuit unit is mounted in the region overlapping the second ground element, the usage of the antenna can be expanded.

In the embodiment of the present invention, the feeding element 30 is formed with a hole portion 32 and a land portion 34, and a circuit portion 36 is connected to the power feeding element 30. However, the present invention is not limited to this, and for example, the hole portion 32, the land portion 34, and the circuit portion 36 may not be included. According to this modification, the structure of the antenna 100 can be simplified.

In the embodiment of the present invention, a plurality of non-feeding elements 50 are arranged around the feeding element 30. However, the present invention is not limited to this, and for example, a plurality of non-feeding elements 50 may not be arranged. According to this modification, the structure of the antenna 100 can be simplified.

In the embodiment of the present invention, the second ground element 20b, the second region 26, and the electric circuit unit 42 are arranged on the dielectric substrate 10. However, the present invention is not limited to this, and for example, the second ground element 20b, the second region 26, and the electric circuit unit 42 may not be arranged. At that time, the dielectric substrate 10 has a substantially square shape. According to this modification, the structure of the antenna 100 can be simplified.

In this embodiment, the slit 22 is formed so as to penetrate the dielectric substrate 10 in the y-axis direction. However, the present invention is not limited to this, and for example, the slit 22 does not have to penetrate the dielectric substrate 10 in the y-axis direction. At that time, a part of the first ground element 20a and the second ground element 20b are connected. According to this modification, the degree of freedom of the structure can be improved.

In the embodiment of the present invention, the antenna 100 is used for the ETC on-board unit, and the resonance frequency of the antenna 100 is in the 5.8 GHz band. However, the present invention is not limited to this, and for example, the intended use and resonance frequency of the antenna 100 may be other than these. According to this modification, the applicable range of the antenna 100 can be expanded.

10 Dielectric board, 12 Front surface, 14 Back surface, 20 Ground element, 22 Slit, 24 1st area, 26 2nd area, 30 Feeding element, 32 Hole part, 34 Land part, 36 Circuit part, 38 Microstrip line, 40 Feed point, 42 electrical circuit section, 44 coaxial cable, 46 through hole section, 50 non-feed element, 60 perturbation section, 100 antenna.

Claims (3)

A dielectric substrate having a first surface and a second surface opposite to the first surface,
A single planar ground element arranged on the first surface and
On the second surface, at least a part of the feeding element is arranged so as to face the one ground element with the dielectric substrate interposed therebetween.
On the second surface, at least a part of the first non-feeding element facing the one ground element with the dielectric substrate interposed therebetween and arranged apart from the feeding element.
On the second surface, at least a part of the second non-feeding element is arranged so as to face the one ground element with the dielectric substrate interposed therebetween and separated from the feeding element.
On the second surface, at least a part of the third non-feeding element is arranged so as to face the one ground element with the dielectric substrate interposed therebetween and separated from the feeding element.
On the second surface, at least a part of the fourth non-feeding element facing the one ground element with the dielectric substrate interposed therebetween and arranged apart from the feeding element.
On the second surface, at least a part thereof faces the one ground element with the dielectric substrate interposed therebetween.
At the same time, it is separated from the power feeding element.
Moreover, the fifth non-feeding element arranged apart from any of the first non-feeding element, the second non-feeding element, the third non-feeding element, and the fourth non-feeding element.
On the second surface, at least a part thereof faces the one ground element with the dielectric substrate interposed therebetween.
At the same time, it is separated from the power feeding element.
Moreover, the sixth is arranged apart from any of the first non-feeding element, the second non-feeding element, the third non-feeding element, the fourth non-feeding element, and the fifth non-feeding element. Passive repeater and
It is an antenna device equipped with at least
At least one of the two outer edge portions intersecting in the feeding element faces the one ground element with the dielectric substrate interposed therebetween, and at least one of the two outer edge portions intersecting in the feeding element. The length of the feeding element in one direction is shorter than ½ of the wavelength at the resonance frequency of the antenna device.
In the first non-feeding element, the first outer edge portion on the side facing the feeding element faces the one ground element with the dielectric substrate interposed therebetween, and the first outer edge of the first non-feeding element. The length of the portion is shorter than the length of the feeding element,
In the second non-feeding element, the second outer edge portion on the side facing the feeding element faces the one ground element with the dielectric substrate interposed therebetween, and the second outer edge of the second non-feeding element. the length of the parts are rather short than the length of the feed element,
In the third non-feeding element, the third outer edge portion on the side facing the feeding element faces the one ground element with the dielectric substrate interposed therebetween, and the third outer edge of the third non-feeding element. The length of the portion is shorter than the length of the feeding element,
In the fourth non-feeding element, the fourth outer edge portion on the side facing the feeding element faces the one ground element with the dielectric substrate interposed therebetween, and the fourth outer edge of the fourth non-feeding element. The length of the portion is shorter than the length of the feeding element,
The feeding element is located between the fifth non-feeding element and the sixth non-feeding element.
The feeding element has a shape having at least a first angle and a second angle facing the first angle in a plan view.
At least a part of the fifth non-feeding element is arranged so as to surround the first corner of the feeding element.
At least a part of the sixth non-feeding element is arranged so as to surround the second corner of the feeding element.
Antenna device. The antenna device according to claim 1.
An AC voltage having a resonance frequency is applied to the feeding element with the one ground element.
Antenna device. The antenna device according to claim 1 or 2.
On the second surface, at least a part thereof faces the one ground element with the dielectric substrate interposed therebetween.
At the same time, it is separated from the power feeding element.
Further, it is separated from any of the first non-feeding element, the second non-feeding element, the third non-feeding element, the fourth non-feeding element, the fifth non-feeding element, and the sixth non-feeding element. hand,
The arranged 7th non-feeding element and
On the second surface, at least a part thereof faces the one ground element with the dielectric substrate interposed therebetween.
At the same time, it is separated from the power feeding element.
Moreover, the first non-feeding element, the second non-feeding element, the third non-feeding element, the fourth non-feeding element, the fifth non-feeding element, the sixth non-feeding element, and the seventh non-feeding element. Further equipped with an eighth non-feeding element, which is arranged apart from any of the elements.
The feeding element is located between the 7th non-feeding element and the 8th non-feeding element, and the shape of the feeding element is a third angle and a fourth angle facing the third angle in a plan view. Have,
At least a part of the 7th non-feeding element is arranged so as to surround the third corner of the feeding element.
At least a part of the eighth non-feeding element is arranged so as to surround the fourth corner of the feeding element.
Antenna device.

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