阅读说明：本技术 天线装置 (Antenna device ) 是由 中岛悠太 王琳 中野久松 于 2019-04-26 设计创作，主要内容包括：一种天线装置(1),其特征在于,具备：电介质基板(10)；接地导体(20),配置于电介质基板(10)的下表面；以及辐射元件(30),配置于电介质基板(10)的上表面,通过两个馈电点收发圆极化波,辐射元件(30)的外缘具有多边形状,在外缘的角部形成有缺口部。(An antenna device (1) is characterized by comprising: a dielectric substrate (10); a ground conductor (20) disposed on the lower surface of the dielectric substrate (10); and a radiation element (30) which is disposed on the upper surface of the dielectric substrate (10) and which receives and transmits circularly polarized waves via two feed points, wherein the outer edge of the radiation element (30) has a polygonal shape, and a notch is formed at the corner of the outer edge.)

1. An antenna device is characterized by comprising:

a dielectric substrate;

a ground conductor disposed on a lower surface of the dielectric substrate; and

a radiation element disposed on the upper surface of the dielectric substrate and configured to receive and transmit circularly polarized waves through two feeding points,

the outer edge of the radiation element has a polygonal shape, and a notch is formed at a corner of the outer edge.

2. The antenna device of claim 1,

the outer edge of the radiating element has a rectangular shape,

the notch portion is formed in at least one of two sets of corner portions of the outer edge, the two sets of corner portions being opposed to each other in a diagonal direction.

3. The antenna device according to claim 1 or 2,

the notch portion is rectangular in shape.

4. The antenna device according to any of claims 1 to 3,

the radiating element has a through hole in the center.

5. The antenna device according to any of claims 1 to 4,

further comprises a parasitic oscillator disposed on the upper surface of the dielectric substrate so as to surround the radiation element,

the outer edge of the parasitic oscillator has a polygonal shape, and a notch is formed at a corner of the outer edge.

6. The antenna device according to claim 5,

the outer edge of the parasitic element has a rectangular shape,

the notch portion of the parasitic oscillator is formed in at least one of two sets of corner portions of an outer edge of the parasitic oscillator, the two sets of corner portions being diagonally opposed to each other.

7. The antenna device according to claim 5 or 6,

the notch portion of the parasitic oscillator has a rectangular shape.

8. An antenna device is characterized by comprising:

a dielectric substrate;

a ground conductor disposed on a lower surface of the dielectric substrate; and

a radiation element disposed on the upper surface of the dielectric substrate and configured to receive and transmit circularly polarized waves through two feeding points,

the outer edge of the radiation element has a polygonal shape, and a protruding portion protruding in the radial outer direction is formed at a corner portion of the outer edge.

Technical Field

The present invention relates to an antenna device.

Background

As a planar antenna, for example, patent document 1 discloses a planar antenna in which a ground conductor and a radiation conductor are arranged to face each other with a dielectric interposed therebetween, wherein a flat radiation conductor and a loop radiation conductor are concentrically arranged on the same plane as the radiation conductor, a part or all of the outer circumference of the loop radiation conductor is connected to the ground conductor, and the flat radiation conductor and the loop radiation conductor have a size such that they are excited in the same mode by mutual coupling in an arbitrary frequency band.

For example, patent document 2 discloses a dual-band shared antenna including a first radiation electrode having an annular shape on a surface of a dielectric substrate and having a center-side end portion short-circuited to a ground electrode on a back surface of the dielectric substrate, a circular second radiation electrode having a center portion short-circuited to the ground electrode on an inner side of the radiation electrode, and the first radiation electrode and the second radiation electrode are operated in different modes and at different frequencies.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 3003272

Patent document 2: japanese patent No. 3020777

Disclosure of Invention

Problems to be solved by the invention

Conventionally, a microstrip antenna is known as a thin antenna. On the other hand, in the case of radiating a circularly polarized wave from an antenna, an axial ratio, which is a ratio of a major axis to a minor axis of the circularly polarized wave, becomes an important parameter.

The invention aims to provide an antenna device which is used as a microstrip antenna, is thin and realizes a good axial ratio.

Means for solving the problems

In order to achieve the above object, an antenna device to which the present invention is applied is characterized by comprising: a dielectric substrate; a ground conductor disposed on a lower surface of the dielectric substrate; and a radiation element disposed on the upper surface of the dielectric substrate and configured to transmit and receive circularly polarized waves through two feeding points, wherein an outer edge of the radiation element has a polygonal shape, and a notch portion is formed at a corner portion of the outer edge.

Here, the outer edge of the radiation element may have a rectangular shape, and the notch portion may be formed at least one of two sets of corners of the outer edge that are diagonally opposite to each other.

Further, the notch portion may have a rectangular shape.

Further, it may be characterized in that the radiation element has a through hole in the center.

In addition, the antenna may further include a parasitic oscillator disposed on the upper surface of the dielectric substrate so as to surround the radiation element, an outer edge of the parasitic oscillator may have a polygonal shape, and a notch may be formed at a corner of the outer edge.

Further, the outer edge of the parasitic oscillator may have a rectangular shape, and the notch portion of the parasitic oscillator may be formed at least one of two sets of corner portions of the outer edge of the parasitic oscillator, the two sets of corner portions being diagonally opposed to each other.

Further, the notch portion of the parasitic oscillator may have a rectangular shape.

From another viewpoint, an antenna device to which the present invention is applied is characterized by comprising: a dielectric substrate; a ground conductor disposed on a lower surface of the dielectric substrate; and a radiation element disposed on an upper surface of the dielectric substrate and configured to transmit and receive circularly polarized waves through two feeding points, wherein an outer edge of the radiation element has a polygonal shape, and a protrusion protruding in a radial outer direction is formed at a corner portion of the outer edge.

Effects of the invention

According to the present invention, it is possible to provide an antenna device which is thin and has a good axial ratio as a microstrip antenna.

Drawings

Fig. 1 is a perspective view of an antenna device according to the present embodiment.

Fig. 2 (a) is a plan view of the antenna device according to the present embodiment as viewed from the top, and fig. 2 (B) is a view showing an example of the cutout portion.

Fig. 3 (a) is a sectional view taken along line a-a of fig. 2 (a), and fig. 3 (B) is a sectional view taken along line B-B of fig. 2 (a).

Fig. 4 is a graph showing values of respective parameters of the antenna device used in the electromagnetic field simulation.

Fig. 5 is a diagram showing VSWR characteristics of the antenna device according to the present embodiment.

Fig. 6 is a diagram showing an AR of the antenna device according to the present embodiment.

Fig. 7 (a) to (C) are diagrams showing an example of the radiation pattern of the antenna device according to the present embodiment.

Fig. 8 (a) to (C) are diagrams showing an example of a radiation pattern of the antenna device without the notch portion.

Fig. 9 (a) and 9 (B) are views showing an example of a configuration in which a protruding portion is provided in an antenna device.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

< construction of antenna device >

First, the structure of the antenna device 1 according to the present embodiment will be described with reference to fig. 1 to 3.

Fig. 1 is a perspective view of an antenna device 1 according to the present embodiment.

Fig. 2 (a) is a plan view of the antenna device 1 according to the present embodiment as viewed from the top, and fig. 2 (B) is a view showing an example of the cutout portion 31A.

Fig. 3 (a) is a sectional view taken along line a-a of fig. 2 (a), and fig. 3 (B) is a sectional view taken along line B-B of fig. 2 (a).

The antenna device 1 includes a dielectric substrate 10, a ground conductor 20, a first radiation element 30, a first feeding point 40, a second feeding point 50, and a second radiation element 60.

For example, the dielectric substrate 10 is a substrate made of a dielectric material such as epoxy glass resin, fluorine resin such as polytetrafluoroethylene, or ceramics. The dielectric substrate 10 has, for example, a rectangular parallelepiped shape having a length L on one side and a thickness h.

The ground conductor 20 is disposed on the lower surface (the surface on the-Z side in fig. 1) of the dielectric substrate 10, and is made of a conductive material such as copper or aluminum. The ground conductor 20 is connected to, for example, a ground line, and supplies a reference potential to the first radiation element 30 and the second radiation element 60. The ground conductor 20 has, for example, a rectangular shape with a side length L.

The first radiation element 30 is disposed on the upper surface (surface on the + Z side in fig. 1) of the dielectric substrate 10 so as to face the ground conductor 20, and operates as a microstrip antenna having the ground conductor 20 as a bottom plate. The first radiating element 30 has, for example, a side length L_aIs rectangular in shape. That is, the outer edge (i.e., the edge of the outer periphery) of the first radiation element 30 has a side length L_aIs rectangular in shape. Further, the first radiation element 30 has a rectangular through hole 32 in the center. The through hole 32 has a length L of one side_hIs rectangular in shape. That is, the inner edge (i.e., the edge of the inner periphery) of the first radiation element 30 has a side length L_aIs rectangular in shape. The dielectric substrate 10 is present on the lower surface of the through-hole 32.

Furthermore, the first radiating element 30 has W₁Is measured. In other words, the width between the outer edge of the rectangular shape of the through hole 32 (i.e., the inner edge of the rectangular shape of the first radiation element 30) and the outer edge of the rectangular shape of the first radiation element 30 is W₁. And, a length L of one side of the first radiation element 30_aIs (2W)₁+L_h) Length of (d).

Further, notches 31A, 31B are formed in one of two sets of corners (a pair of upper left and lower right corners in the example shown in fig. 2 a) of the outer edge of the first radiation element 30, which are respectively opposed in the diagonal direction.

As shown in fig. 2 (B), the notch 31A has, for example, a length S of one side_xAnd S_yIs rectangular in shape. Further, the cutout 31B also has the same shape as the cutout 31A.

The first radiation element 30 is formed of a conductive material such as copper or aluminum, and is processed into a predetermined shape by etching or the like.

The first feeding point 40 is connected to the signal generator disposed directly below the ground conductor 20 via a feeding line 41 penetrating the dielectric substrate 10The connector 70 is connected to receive power from the signal generator 70 through the power supply line 41. As shown in fig. 2 a, the first feeding point 40 is arranged at a coordinate (X) in an orthogonal coordinate system set with the center position of the upper surface (surface on the + Z side in fig. 1) of the dielectric substrate 10 as an origin O_a，Y_a) The position of (a).

Similarly to the first feeding point 40, the second feeding point 50 is connected to the signal generator 70 disposed directly below the ground conductor 20 via a feeding line 51 penetrating the dielectric substrate 10, and is fed from the signal generator 70 via the feeding line 51. As shown in fig. 2 a, the second feeding point 50 is arranged at a coordinate (X) on the upper surface (surface on the + Z side in fig. 1) of the dielectric substrate 10_b，Y_b) The position of (a).

Here, in the case of feeding power from the signal generator 70 to the first feeding point 40 and the second feeding point 50, a signal of a common frequency is transmitted from the signal generator 70 to the first feeding point 40 and the second feeding point 50. However, the phase of the signal transmitted from the signal generator 70 to the second feeding point 50 is delayed by 90 degrees with respect to the phase of the signal transmitted to the first feeding point 40. Thus, by shifting the phases of the two signals by 90 degrees, radiation of a circularly polarized wave is realized at the first radiation element 30. The circularly polarized wave is radiated from the first radiation element 30 in the + Z side direction and the-Z side direction.

In order to radiate circularly polarized waves, the two signals transmitted from the signal generator 70 may be shifted in phase. Therefore, the phase of the signal transmitted from the signal generator 70 to the first feeding point 40 may be delayed by 90 degrees with respect to the phase of the signal transmitted from the signal generator 70 to the second feeding point 50.

In other words, the rotation direction of the plane of polarization of the circularly polarized wave is determined by delaying the phase of which of the two signals transmitted from the signal generator 70. For example, in the case where the phase of the signal transmitted from the signal generator 70 to the second feeding point 50 is delayed by 90 degrees with respect to the phase of the signal transmitted from the signal generator 70 to the first feeding point 40, the right-hand circularly polarized wave is radiated in the + Z-side direction and the left-hand circularly polarized wave is radiated in the-Z-side direction in the first radiating element 30. On the other hand, in the case where the phase of the signal transmitted from the signal generator 70 to the first feeding point 40 is delayed by 90 degrees with respect to the phase of the signal transmitted from the signal generator 70 to the second feeding point 50, the left-hand circularly polarized wave is radiated in the + Z side direction and the right-hand circularly polarized wave is radiated in the-Z side direction in the first radiating element 30.

Further, as long as the circularly polarized wave is radiated by the first radiation element 30, the deviation of the phases of the two signals transmitted from the signal generator 70 may not be 90 degrees. However, by making the phase deviation close to 90 degrees, the accuracy of the circle of the circularly polarized wave is improved.

Further, the positions of the first feeding point 40 and the second feeding point 50 may be changed as long as the circularly polarized wave is radiated from the first radiation element 30.

Similarly to the first radiation element 30, the second radiation element 60 is disposed on the upper surface (surface on the + Z side in fig. 1) of the dielectric substrate 10 so as to face the ground conductor 20, and operates as a microstrip antenna having the ground conductor 20 as a bottom plate. The second radiating element 60 is a parasitic element having no feeding point, and has a ring shape surrounding the first radiating element 30. The second radiation element 60 is disposed around the first radiation element 30 with a gap 62 formed by a gap having a width g so as to electromagnetically couple with the first radiation element 30. The second radiating element 60 has a W_RNGIs measured.

In other words, the second radiation element 60 is disposed on the upper surface (surface on the + Z side in fig. 1) of the dielectric substrate 10 so as to surround the periphery of the first radiation element 30, and the outer edge and the inner edge of the second radiation element 60 have a rectangular shape. Further, the inner edge of the rectangular shape of the second radiating element 60 and the outer edge of the rectangular shape of the first radiating element 30 are separated by a gap 62. Also, the second radiation element 60 operates in a non-feeding manner by electromagnetic coupling with the first radiation element 30.

Similarly to the first radiation element 30, notches 61A and 61B are formed in the second radiation element 60 in the diagonal direction of the outer edge thereof. The notched portions 61A, 61B are formed at one of two sets of corners of the second radiation element 60 that are respectively opposed in the diagonal direction (a pair of upper left and lower right corners in the example shown in fig. 2 (a)). Further, the notched portions 61A, 61B have the same rectangular shape as the notched portion 31A shown in fig. 2 (B).

The second radiation element 60 is formed of a conductive material such as copper or aluminum, and is processed into a predetermined shape by etching or the like.

Here, when the first feeding point 40 and the second feeding point 50 are fed from the signal generator 70, the first radiating element 30 and the second radiating element 60 are electromagnetically coupled. By this electromagnetic coupling, the second radiation element 60 is excited, and circular polarized wave radiation is realized in the second radiation element 60. The circularly polarized wave is radiated from the second radiation element 60 in the + Z side direction and the-Z side direction.

In other words, the direction of rotation of the plane of polarization of the circularly polarized wave is determined by delaying the phase of which of the two signals transmitted from the signal generator 70, as with the first radiation element 30. For example, in the case where the phase of the signal transmitted from the signal generator 70 to the second feeding point 50 is delayed by 90 degrees with respect to the phase of the signal transmitted from the signal generator 70 to the first feeding point 40, in the second radiation element 60, the right-hand circularly polarized wave is radiated in the + Z side direction and the left-hand circularly polarized wave is radiated in the-Z side direction. On the other hand, in the case where the phase of the signal transmitted from the signal generator 70 to the first feeding point 40 is delayed by 90 degrees with respect to the phase of the signal transmitted from the signal generator 70 to the second feeding point 50, the left-hand circularly polarized wave is radiated in the + Z-side direction and the right-hand circularly polarized wave is radiated in the-Z-side direction in the second radiating element 60.

< calculation result based on electromagnetic field simulation >

The antenna device 1 of the present embodiment was calculated by electromagnetic field simulation. Fig. 4 is a diagram showing values of respective parameters of the antenna device 1 used in the electromagnetic field simulation. The values of the parameters shown in fig. 4 are examples, and the values of the parameters of the antenna device 1 are not limited to those shown in fig. 4.

As shown in fig. 4, L is 37.74mm, W₁＝6.275mm、W_RNG＝0.8mm、L_h＝4.12mm、h＝15mm、X_a＝3.225mm、Y_a＝4.254mm、X_b＝－4.32mm、Y_b＝3.02mm、ε_r＝20.0、g＝1.0mm、S_x＝0.5mm、S_y＝0.5mm。

Note that ε_rIs the relative permittivity of the dielectric substrate 10.

Next, the calculation results of the electromagnetic field simulation will be described with reference to fig. 5 to 8. In the examples shown in fig. 5 to 8, the respective parameters shown in fig. 4 are used.

Fig. 5 is a diagram showing VSWR (Voltage Standing Wave Ratio) characteristics of the antenna device 1 according to the present embodiment. Here, the antenna device 1 having the notches 31A and 31B and the notches 61A and 61B is compared with an antenna device not having the notches 31A and 31B and the notches 61A and 61B (hereinafter, referred to as "notch-free antenna device"). In the antenna device without a notch portion, the shape is the same as that of the antenna device 1 except for the notch portions 31A and 31B and the notch portions 61A and 61B. That is, in the antenna device without the notch portion, the parameters shown in fig. 4 except for S are used_xAnd S_yAnd (3) other parameters.

The horizontal axis of the graph of fig. 5 represents the frequency of the signal transmitted from the signal generator 70. The vertical axis indicates the VSWR characteristics of the radio wave generated from the antenna device 1 or the antenna device without a notch. In the example shown in fig. 5, "notched portion" indicates the VSWR characteristic of the antenna device 1, and "no notched portion" indicates the VSWR characteristic of the antenna device without a notched portion.

Here, the VSWR characteristic is one of indexes indicating high-frequency characteristics, and means a degree of reflection of a part of a signal on a circuit when a high-frequency signal passes through. The greater the reflection, the greater the value of the VSWR, indicating greater signal loss (i.e., return loss). Therefore, generally speaking, VSWR is required to be as low as possible.

As shown in the figure, it was confirmed that the antenna device 1 and the antenna device without the notch portion have two resonance frequencies. Specifically, the antenna device 1 has two resonance frequencies, i.e., a frequency band of 1.18 to 1.23GHz and a frequency band of 1.58 GHz. That is, when the frequencies of the signals transmitted from the signal generator 70 to the first feeding point 40 and the second feeding point 50 are, for example, the 1.18GHz band, the 1.23GHz band, and the 1.58GHz band, the antenna device 1 radiates circularly polarized waves.

The 1.18GHz band, the 1.23GHz band, and the 1.58GHz band are referred to as an L5 band, an L2 band, and an L1 band, respectively, and are bands used in GNSS (Global Navigation Satellite System), for example.

In other words, the perimeter of the rectangular shape of the second radiating element 60 is longer than the perimeter of the rectangular shape of the first radiating element 30. Therefore, the second radiating element 60 operates as an antenna element resonating at a low frequency band, as compared to the first radiating element 30. In this example, the second radiating element 60 operates as an antenna element that resonates in a frequency band of 1.18 to 1.23 GHz. On the other hand, the first radiating element 30 operates as an antenna element that resonates in the frequency band of 1.58 GHz.

Here, the first radiating element 30 is fed by the first feeding point 40 and the second feeding point 50, and a current flows in a circumferential direction of the rectangular shape of the first radiating element 30, whereby the first radiating element 30 resonates at a specific frequency. The resonance frequency is mainly affected by the length of the outer edge of the rectangular shape of the first radiating element 30 as a path through which the current flows.

To explain this, for example, even in a configuration in which the through-hole 32 is not provided in the first radiation element 30, a circularly polarized wave can be radiated from the first radiation element 30 by feeding power to the first feeding point 40 and the second feeding point 50. However, in the configuration in which the through hole 32 is provided in the first radiation element 30 as in the present embodiment, the current does not flow in the vicinity of the center of the first radiation element 30. Therefore, the path through which the current flows becomes long, and the resonant frequency of the first radiation element 30 becomes low. Further, by enlarging the through-hole 32, a region in which current does not flow becomes large. Therefore, the path through which the current flows becomes long, and the resonant frequency of the first radiation element 30 becomes low.

In this way, the resonant frequency is adjusted by the through hole 32 of the first radiation element 30.

Next, fig. 6 is a diagram showing AR (Axial Ratio) of the antenna device 1 according to the present embodiment. AR is axial ratio. For example, when AR is 1, a circle having a major axis and a minor axis equal to each other is shown. If it is considered desirable that the circularly polarized wave is as close to a circle as possible, it is required to make AR close to 1. In the example shown in fig. 6, since the unit of AR is dB, when AR is 0dB, the major axis and the minor axis of the circularly polarized wave are equal to each other.

In the example shown in fig. 6, "notched portion" shows the AR of the antenna device 1, and "non-notched portion" shows the AR of the antenna device without a notched portion.

As shown in the figure, it was confirmed that the AR of the antenna device 1 was smaller than that of the antenna device without the notch portion in the frequency band of 1.1 to about 1.6 GHz. For example, in a frequency band of 1.18 to 1.23GHz, or a frequency band of 1.58GHz of the resonance frequency of the antenna device 1, the AR of the antenna device 1 is smaller than that of an antenna device without a notch. For example, in a frequency band other than the resonance frequency, the AR of the antenna device 1 is smaller than that of an antenna device without a notch.

By providing the notches 31A and 31B and the notches 61A and 61B in this manner, the axial ratio is improved.

In other words, by feeding at two points of the first feeding point 40 and the second feeding point 50, cross polarized wave components having a phase difference of about 90 degrees are generated. The cross polarized wave component here is a component of the horizontally polarized wave with respect to the vertically polarized wave (or a component of the vertically polarized wave with respect to the horizontally polarized wave). Therefore, when the signal generator 70 applies a 90-degree phase difference to the first feeding point 40 and the second feeding point 50 to perform feeding, a 90-degree phase difference is further applied to the cross polarized wave component, and thus polarized waves that are mutually intensified (i.e., vertical polarized waves, horizontal polarized waves) and polarized waves that are mutually weakened (i.e., vertical polarized waves, horizontal polarized waves) are generated. As a result, the axial ratio of the circularly polarized wave deteriorates.

Here, when the notches 31A and 31B are provided, a difference occurs in the length of the path through which the current flows between the corner portion having the notches 31A and 31B and the corner portion having no notches 31A and 31B at the outer edge of the first radiation element 30. That is, by providing the notches 31A and 31B, the length of the corner portions of the notched portions 31A and 31B in the diagonal direction (that is, the length of the outer edge diagonal lines of the corner portions of the notched portions 31A and 31B) changes at the outer edge of the first radiation element 30, and a difference is generated between the length of the corner portions of the non-notched portions 31A and 31B in the diagonal direction. In other words, a difference is generated in the length of the outer edge of the first radiation element 30 in each diagonal direction. As a result, the phase of the cross polarized wave component is shifted, and the degree of mutual enhancement and mutual attenuation of the polarized waves are suppressed. Thereby, the accuracy of the circle of the circularly polarized wave radiated from the first radiation element 30 is improved, and the axial ratio is improved.

Similarly, when the notches 61A and 61B are provided, a difference occurs in the length of the path through which the current flows between the corner having the notches 61A and 61B and the corner having no notches 61A and 61B at the outer edge of the second radiation element 60. That is, by providing the notches 61A and 61B, the length in the diagonal direction of the corner portion having the notches 61A and 61B (i.e., the length in the diagonal line of the outer edge of the second radiation element 60) changes at the outer edge of the second radiation element 60, and a difference occurs in the length in the diagonal direction of the outer edge of the second radiation element 60. As a result, the accuracy of the circle of the circularly polarized wave radiated from the second radiation element 60 is improved, and the axial ratio is improved.

For example, when the target value of AR is 3, if "notched portion" and "non-notched portion" are compared at 1.1 to about 1.6GHz, the range of AR of "notched portion" to 3 or less of the target value is wide. For example, in the frequency band of 1.18 to 1.23GHz, the "notched part" is wider than the "unnotched part" in the range where AR is equal to or less than the target value 3. Therefore, by providing the notches 31A and 31B and the notches 61A and 61B, the antenna device can be said to operate as a wider-band antenna.

Next, fig. 7 is a diagram showing an example of the radiation pattern of the antenna device 1 according to the present embodiment. On the other hand, fig. 8 is a diagram showing an example of a radiation pattern of the antenna device without the notch portion. Here, the examples shown in fig. 7 and 8 show the radiation patterns of the XZ plane of fig. 1. In fig. 7 and 8, normalization is performed so that the maximum gain is 0 dB.

As shown in fig. 7, it was confirmed that in the antenna device 1 of the present embodiment, the directivity characteristic of radiation in the + Z direction is obtained for the left-hand circularly polarized wave and the directivity characteristic of radiation in the-Z direction is obtained for the right-hand circularly polarized wave in the 1.18GHz band, the 1.23GHz band, and the 1.58GHz band. As shown in fig. 8, it was confirmed that, in the antenna device without a notch, directivity characteristics of radiation in the + Z direction were obtained for the left-hand circularly polarized wave and directivity characteristics of radiation in the-Z direction were obtained for the right-hand circularly polarized wave in the 1.18GHz band, 1.23GHz band, and 1.58GHz band.

However, as shown in fig. 8 (C), in the antenna device without a notch portion, at 1.58GHz, θ is about 30 degrees, the left-hand circularly polarized wave is radiated in the + Z direction, and the right-hand circularly polarized wave is also radiated in the + Z direction. On the other hand, as shown in fig. 7 (C), in the antenna device 1, at 1.58GHz, the left-hand circularly polarized wave is radiated in the + Z side direction, and the right-hand circularly polarized wave is radiated in the-Z side direction, and even at θ of about 30 degrees, the right-hand circularly polarized wave is not radiated in the + Z side direction.

Therefore, from the viewpoint of the radiation pattern, it was confirmed that the axial ratio was improved in the direction in which θ was about 30 degrees, for example, by providing the notches 31A and 31B and the notches 61A and 61B.

In the above example, the ground conductor 20 has the same size (i.e., a rectangular shape having a side length L) as the lower surface (the surface on the-Z side in fig. 1) of the dielectric substrate 10. Here, if the ground conductor 20 is provided larger than the lower surface of the dielectric substrate 10, a circularly polarized wave radiated in the-Z direction may be reflected by the ground conductor 20. For example, if a right-hand circularly polarized wave radiated to the-Z side direction is reflected by the ground conductor 20, the radiation direction becomes the + Z side direction, and the circularly polarized wave is changed from the right-hand circularly polarized wave to the left-hand circularly polarized wave.

As described above, the antenna device 1 of the present embodiment radiates circularly polarized waves in the first radiation element 30 and the second radiation element 60 by feeding power to the first feeding point 40 and the second feeding point 50. Further, by providing notches 31A and 31B in the first radiation element 30 and notches 61A and 61B in the second radiation element 60, the axial ratio of the circularly polarized wave is improved. Since the antenna device 1 has the configuration in which the second radiation element 60 as a parasitic element is disposed on the upper surface of the dielectric substrate 10, it is thinner than a configuration in which a parasitic element is disposed not on the upper surface of the dielectric substrate 10 but in the radiation direction of a circularly polarized wave (for example, the + Z direction) of the dielectric substrate 10.

< modification example >

In the above example, the notches 31A and 31B are provided at one of the two diagonally opposed corner portions of the outer edge of the first radiation element 30, and the notches 61A and 61B are provided at one of the two diagonally opposed corner portions of the outer edge of the second radiation element 60.

For example, the notch portion may be provided in both of two sets of corner portions of the outer edge of the first radiation element 30 that are diagonally opposed to each other (i.e., all four corner portions of the outer edge). However, in order to provide a difference in length in each diagonal direction of the outer edge of the first radiation element 30, it is sufficient to provide different notched portions in one set of corner portions and the other set of corner portions of the outer edge of the first radiation element 30, which are respectively opposed in the diagonal direction, instead of providing completely identical notched portions in the four corner portions of the outer edge of the first radiation element 30. For example, the notch may be provided only at one corner of the outer edge, or at three corners.

Similarly, for example, notches may be provided in both of two sets of corners of the outer edge of the second radiation element 60 that are diagonally opposed to each other (i.e., all four corners of the outer edge). However, in order to provide a difference in length in each diagonal direction of the outer edge of the second radiation element 60, it is sufficient to provide different notched portions in one set of corner portions and the other set of corner portions of the outer edge of the second radiation element 60, which are respectively opposed in the diagonal direction, instead of providing completely identical notched portions in the four corner portions of the outer edge of the second radiation element 60. For example, the notch may be provided only at one corner of the outer edge, or at three corners.

In addition, the notch may be provided only in one of the first radiation element 30 and the second radiation element 60, and the notch may not be provided in the other.

For example, the notches 31A and 31B may be provided in the first radiation element 30, and the notches 61A and 61B may not be provided in the second radiation element 60.

In the above example, the notch portions 31A and 31B; the shape of the notches 61A and 61B is a square rectangular shape, but is not limited to such a configuration.

For example, the notch portions 31A and 31B; the notches 61A and 61B have a non-square rectangular shape or a triangular shape obtained by cutting off the corners of the first radiation element 30 and the second radiation element 60.

In the above example, the first radiation element 30 and the second radiation element 60 are formed in a square rectangular shape, but the present invention is not limited to such a configuration. In the present embodiment, the shapes of the first radiation element 30 and the second radiation element 60 may be changed as long as the circularly polarized waves are radiated to the first radiation element 30 and the second radiation element 60. For example, the first radiation element 30 and the second radiation element 60 may be formed in a rectangular shape having a non-square rectangular shape or a polygonal shape other than a rectangular shape.

In other words, when the first radiation element 30 and the second radiation element 60 are polygonal shapes other than a rectangle, the notch portion is formed at least one corner portion of the outer edge of the first radiation element 30 and at least one corner portion of the outer edge of the second radiation element 60.

For example, when the first and second radiation elements 30 and 60 are each a 2 n-sided polygon (n is an integer of 3 or more), the notch portion is formed in at least one set of corners of the outer edge of the first radiation element 30 that face each other in the diagonal direction and at least one set of corners of the outer edge of the second radiation element 60 that face each other in the diagonal direction.

In the above example, the dielectric substrate 10 has the same shape (i.e., a rectangular shape) as the first and second radiation elements 30 and 60, but is not limited to such a configuration. In the present embodiment, the dielectric substrate 10 may have a shape different from the first radiation element 30 and the second radiation element 60. The dielectric substrate 10 may have a circular shape or a polygonal shape other than a rectangular shape.

In the above example, the through-hole 32 has a square rectangular shape, but is not limited to such a configuration. In the present embodiment, the shape of the through hole 32 may be changed as long as the first radiation element 30 radiates circularly polarized waves. For example, the through-hole 32 may have a rectangular shape, which is a non-square rectangle, or a circular shape.

In the above example, the second radiation element 60 is disposed around the first radiation element 30, but the second radiation element 60 may not be disposed in the present embodiment. In this case, the antenna device 1 has a single resonance type characteristic, not a double resonance type characteristic. For example, in the example shown in FIG. 5, no resonance occurs in a frequency band of 1.18 to 1.23GHz (i.e., corresponding to the resonance frequency of the second radiating element 60).

In the above example, the case of transmitting a circularly polarized wave has been described as an example, but the antenna device 1 of the present embodiment can be applied to a case of receiving a circularly polarized wave transmitted from a radio base station, for example.

Other example of improving the axial ratio of a circularly polarized wave

In the above example, the first radiation element 30 has the notches 31A and 31B, and the second radiation element 60 has the notches 61A and 61B. However, in order to improve the axial ratio of the circularly polarized wave, the notch portions 31A and 31B are not limited to be formed; the notches 31A and 31B are formed.

For example, instead of the notches 31A and 31B, projections projecting in the radial outer direction may be formed; notches 61A and 61B.

Fig. 9 is a diagram showing an example of a configuration in which a protruding portion is provided in the antenna device 1.

In the example shown in fig. 9, the protruding portion 33A and the protruding portion 33B are formed at one of two sets of corners of the outer edge of the first radiation element 30, which are diagonally opposed to each other. Further, a projection 63A and a projection 63B are formed at one of two sets of corners of the outer edge of the second radiation element 60, which are respectively opposed in the diagonal direction.

In the example shown in fig. 9 (B), the protrusion 33A has a square rectangular shape with one side lengths S1 and S2, and S1 is equal to S2. Further, as for the lengths S3, S4 of the portions protruding from the first radiation element 30, there is S3 — S4. However, S3 and S4 may be different. The protruding portion 33B and the protruding portions 63A and 63B also have the same shape as the protruding portion 33A.

By providing the protruding portions 33A and 33B in this manner, a difference in the length of the path through which the current flows is generated between the corner portion having the protruding portions 33A and 33B and the corner portion having no protruding portions 33A and 33B at the outer edge of the first radiation element 30. That is, the length in the diagonal direction of the corner portion having the protruding portion 33A, 33B (i.e., the length of the outer edge diagonal line of the corner portion having the protruding portion 33A, 33B) changes at the outer edge of the first radiation element 30, and a difference is generated between the length in the diagonal direction of the corner portion having no protruding portion 33A, 33B. As a result, the accuracy of the circle of the circularly polarized wave radiated from the first radiation element 30 is improved, and the axial ratio is improved. Similarly, by providing the protruding portions 63A and 63B, the accuracy of the circle of the circularly polarized wave radiated from the second radiation element 60 is improved, and the axial ratio is improved.

In this example, the projections 33A and 33B are provided at one of the two diagonally opposed corner portions of the outer edge of the first radiation element 30, and the notches 63A and 63B are provided at one of the two diagonally opposed corner portions of the outer edge of the second radiation element 60. The protruding portion can be formed in the same manner as the notch portion.

For example, similarly to the notch portion, a protruding portion may be provided on both of two sets of corner portions of the outer edge of the first radiation element 30 that are diagonally opposed to each other (i.e., all four corner portions of the outer edge). In this case, different projections may be provided on one of the two sets of corners and the other set of corners. Further, for example, the protrusion may be provided only at one corner of the outer edge of the first radiation element 30, or may be provided at three corners. Further, the notch portion may be provided at one of the two sets of corner portions, and the protrusion portion may be provided at the other set of corner portions.

For example, the protruding portions may be provided on both two sets of corners of the outer edge of the second radiation element 60 that are diagonally opposed to each other (i.e., all four corners of the outer edge). In this case, different projections may be provided on one of the two sets of corners and the other set of corners. Further, for example, the protrusion may be provided only at one corner of the outer edge of the second radiation element 60, or may be provided at three corners. Further, the notch portion may be provided at one of the two sets of corner portions, and the protrusion portion may be provided at the other set of corner portions.

In addition, a projection may be provided only on one of the first radiation element 30 and the second radiation element 60, and no projection may be provided on the other.

For example, the first radiation element 30 may be provided with the protruding portions 33A and 33B, and the second radiation element 60 may be provided with no protruding portions 63A and 63B.

In the above example, the projections 33A and 33B; the shape of the protruding portions 63A, 63B is a square rectangular shape, but is not limited to such a configuration.

For example, the projections 33A and 33B; the shape of the projections 63A, 63B is a rectangular shape having a non-square rectangular shape, or a polygonal shape or a circular shape other than a rectangular shape.

In the case where the first radiation element 30 and the second radiation element 60 are polygonal shapes other than the rectangular shape, the protruding portions are formed on at least one corner portion of the outer edge of the first radiation element 30 and at least 1 corner portion of the outer edge of the second radiation element 60, similarly to the notch portions.

For example, in the case where the first and second radiation elements 30 and 60 are each a 2 n-sided polygon (n is an integer of 3 or more), the projections are formed on at least one set of corners of the outer edge of the first radiation element 30 that are opposed to each other in the diagonal direction and at least one set of corners of the outer edge of the second radiation element 60 that are opposed to each other in the diagonal direction.

Although various embodiments and modifications have been described above, it is needless to say that these embodiments and modifications may be combined with each other.

The above-described embodiments do not limit the present disclosure in any way, and can be implemented in various ways without departing from the scope of the present disclosure.

Description of reference numerals:

1: an antenna device;

10: a dielectric substrate;

20: a ground conductor;

30: a first radiating element;

31A, 31B: a notch portion;

32: a through hole;

40: a first feeding point:

50: a second feeding point;

60: a second radiating element;

61A, 61B: a notch portion;

62: a void.