Antenna device

Abstract

To provide an antenna device capable of realizing an isolation of 20 dB while maintaining a miniaturization.SOLUTION: An antenna device comprises: a first outer antenna element 2 and a first inner side antenna element 3 in a semicircular arc shape, formed in one surface of an insulation substrate 1 in a same core shape; a second outer side antenna element 19 and a second inner side antenna element 20 in a semicircular arc shape formed on the other surface of the insulation substrate in the same core shape; an antenna side coupling part 17 that is formed in the one surface of the insulation substrate; and a power supply binding part 18 which is formed in a posture reversed in 180 degrees with a coupling part to the other surface of the insulation substrate. The first outer side antenna element and the second outer side antenna element are coupled to an antenna side coupling part via connection lines 4 and 10 and a first through hole 15, and the first inner side antenna element and the second inner side antenna element are coupled to the antenna side coupling part via connection lines 5 and 11 and a second through hole 14.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an antenna device equipped with a circularly polarized antenna that supports a plurality of frequency bands. [Background technology]

[0002] In mobile phones and wireless LANs (Local Area Networks), multiple antennas that support the same frequency are connected to a single radio using a communication method known as MIMO (Multiple Input Multiple Output). MIMO is a wireless communication technology that achieves high throughput and highly reliable communication by configuring both transmission and reception with multiple antennas, but when actually designing a system, the problem becomes how to implement multiple antennas in a terminal that must be made small.

[0003] As an example of this type of antenna device, Patent Document 1 describes a substrate-type antenna in which an arc-shaped antenna element is composed of a first arc-shaped antenna element and a second arc-shaped antenna element, and the first arc-shaped antenna element and the second arc-shaped antenna element each have, from the outer periphery to the inner periphery of the arc-shaped antenna element, an integrated antenna element corresponding to three frequency bands and a standalone antenna element corresponding to one frequency band that is arranged at an interval from the integrated antenna element, and the substrate-type antenna has a plurality of connectors to which the first arc-shaped antenna element and the second arc-shaped antenna element are respectively joined, and a connecting portion to which the plurality of connectors are coupled.

[0004] The antenna device described in Patent Document 1 has a first arc-shaped antenna element (long arc-shaped antenna element) and a second arc-shaped antenna element (short arc-shaped antenna element) formed concentrically around a central point on the surface of a substrate, with the long arc-shaped antenna element and the short arc-shaped antenna element divided so as to face each other at a distance. Each of the long arc-shaped antenna element and the short arc-shaped antenna element has an outer integrated antenna element corresponding to three frequency bands and a standalone antenna element corresponding to one frequency band arranged at a distance inside the integrated antenna element. A coupler is formed in the center of the surface of the substrate. The coupler has four oval-shaped coupling elements arranged at a distance from each other, with the coupling elements having a separating portion separated by a gap. The long arc-shaped antenna element and the short arc-shaped antenna element are joined at the separating portion of each coupling element using individual connection patterns.

[0005] Specifically, the outermost coupling element is connected to the single antenna element of the long arc-shaped antenna element and the integrated antenna element of the short arc-shaped antenna element by one connection pattern, the innermost coupling element is connected to the integrated antenna element of the long arc-shaped antenna element and the single antenna element of the short arc-shaped antenna element by another connection pattern, and the remaining two coupling elements are connected to the integrated antenna element of the long arc-shaped antenna element and the integrated antenna element of the short arc-shaped antenna element by another connection pattern.In this way, the long arc-shaped antenna element and the short arc-shaped antenna element are connected to each coupling element of the coupler by four connection patterns, and as a whole, they are configured as a dipole-type circularly polarized antenna. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-54525 Summary of the Invention [Problem to be solved by the invention]

[0007] In the antenna device described in Patent Document 1, a long arc-shaped antenna element and a short arc-shaped antenna element are divided on the surface of a substrate and arranged concentrically opposite each other. By adjusting the total length of these long arc-shaped antenna elements and short arc-shaped antenna elements, the antenna axial ratio (AR) can be adjusted to 3 dB or less (antenna isolation of 15 dB or less) required for circular polarization. However, because the antenna structure combines a circularly polarized antenna in which a standalone antenna element on the inside of the long arc-shaped antenna element and an integrated antenna element on the outside of the short arc-shaped antenna element are joined by a connection pattern, and a circularly polarized antenna in which a standalone antenna element on the inside of the short arc-shaped antenna element and an integrated antenna element on the outside of the long arc-shaped antenna element are joined by a different connection pattern, it has been difficult to achieve inter-antenna isolation of 20 dB or more, which is required for 5G mobile phone terminals, Wi-Fi 6 (IEEE802.11ax), etc.

[0008] The present invention has been made in consideration of the current state of the prior art, and its purpose is to provide an antenna device that can achieve isolation of 20 dB or more while maintaining compact size. [Means for solving the problem]

[0009] In order to achieve the above object, one aspect of the present invention is an antenna device in which two dipole circularly polarized antennas corresponding to different frequency bands are arranged on the same insulating substrate, the antenna device comprising: a first outer antenna element and a first inner antenna element formed on one surface of the insulating substrate in semicircular arc shapes with different radii and a same center point as the center; a second outer antenna element and a second inner antenna element formed on another surface of the insulating substrate in semicircular arc shapes with different radii and a same center point as the center; and a first connecting element formed on the one surface of the insulating substrate and connecting the first outer antenna element and the second outer antenna element via a through hole provided in the insulating substrate. a second connection line formed on the one surface of the insulating substrate and connecting the first inner antenna element and the second inner antenna element via a through hole provided in the insulating substrate; a coupling portion formed on the one surface of the insulating substrate so as to couple the first connection line and the second connection line; and a feed coupling portion formed on the other surface of the insulating substrate so as to face the coupling portion, wherein the first outer antenna element and the second outer antenna element are arranged on the same arc so as to be continuous in an annular shape in a plan view, and the first inner antenna element and the second inner antenna element are arranged on the same arc so as to be continuous in an annular shape in a plan view. arc placed on top the coupling portion has a first coupling element to which the first connection line is connected and a second coupling element to which the second connection line is connected, the first coupling element and the second coupling element are each formed in an elliptical shape with a divided portion, the second coupling element is arranged inside the first coupling element at a distance, the second inner antenna element has an overlapping portion that overlaps a portion of the first inner antenna element in a plan view, a third coupling element having an elliptical shape with a divided portion is arranged inside the second coupling element at a distance, and a third connection line joined to the third coupling element is connected to the overlapping portion via a through hole provided in the insulating substrate. It is characterized by the following. [Effects of the Invention]

[0010] According to the antenna device of the present invention, it is possible to achieve isolation of 20 dB or more while maintaining a small size. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a plan view showing an antenna pattern of the antenna device according to the embodiment. [Figure 2] FIG. 2 is a rear view showing an antenna pattern of the antenna device according to the embodiment. [Figure 3] FIG. 3 is a perspective view of the antenna pattern insulating substrate shown in FIGS. 1 and 2 as viewed from above. [Figure 4]10A and 10B are explanatory diagrams illustrating a case where the antenna device according to the embodiment operates as a right-handed circularly polarized antenna. [Figure 5] 10A and 10B are explanatory diagrams illustrating a case where the antenna device according to the embodiment operates as a left-handed circularly polarized antenna. [Figure 6] 6 is an explanatory diagram showing a state in which the two antenna devices shown in FIGS. 4 and 5 are arranged in close proximity to each other. FIG. [Figure 7] 7 is a graph showing the standing wave ratio (VSWR value) of the two antennas shown in FIG. 6. [Figure 8] 7 is a graph showing isolation between the two antennas shown in FIG. 6. [Figure 9] 7 is a graph showing maximum and average values ​​of gain in the 2.4 GHz band and the 5 GHz band for the two antennas shown in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0013] The antenna device according to this embodiment is an antenna device compatible with MIMO antennas in the 2.4 GHz band (2400 to 2484 MHz) and 5 GHz band (5150 to 5250 MHz, 5250 to 5350 MHz, 5470 to 5725 MHz) of Wi-Fi6.

[0014] Fig. 1 is a plan view showing the antenna pattern of the antenna device according to this embodiment, Fig. 2 is a rear view showing the antenna pattern of the antenna device, and Fig. 3 is a perspective view of the antenna patterns shown in Fig. 1 and Fig. 2, seen from above on an insulating substrate. The antenna device shown in Figs. 1 to 3 is a dipole circularly polarized antenna for Wi-Fi 6, in which two arc-shaped antenna elements, which are the minimum configuration of multiple antenna elements, are arranged on the front and back surfaces of an insulating substrate.

[0015] 1, a first outer antenna element 2, a first inner antenna element 3, and an antenna-side coupling portion 17 are formed on a surface 1A of an insulating substrate 1. The insulating substrate 1 is a plate-shaped body made of a dielectric material such as glass epoxy resin, and in this embodiment, an FR-4 substrate (plate thickness: 0.3 mm) with a dielectric constant of 4.3 is used.

[0016] The first outer antenna element 2 and the first inner antenna element 3 are formed in semicircular arc shapes with different radii centered on the same center point O. The first inner antenna element 3 is disposed inside the first outer antenna element 2 at a distance, and the arc length of the first outer antenna element 2 is set to be sufficiently longer than the arc length of the first inner antenna element 3.

[0017] Antenna-side coupling section 17 has three coupling elements 7, 8, and 9 arranged around center point O, and these coupling elements 7, 8, and 9 are spaced apart from one another and formed into an elliptical shape. If the three coupling elements are designated, from the outside, as first coupling element 7, second coupling element 8, and third coupling element 9, each of the first to third coupling elements 7, 8, and 9 is partially separated to form gap 13.

[0018] The first outer antenna element 2 is connected to a first coupling element 7 via a first connection line 4, and is further connected to a first through-hole 15 via another first connection line 10. The first inner antenna element 3 is connected to a second coupling element 8 via a second connection line 5, and is further connected to a second through-hole 14 via another second connection line 11. A pair of third connection lines 6 and 12 are connected to the third coupling element 9, and these third connection lines 6 and 12 are not connected to the first outer antenna element 2 or the first inner antenna element 3, but one of the third connection lines 12 is connected to a third through-hole 16. The first to third through-holes 14, 15, and 16 are formed by plating through-holes drilled in the insulating substrate 1.

[0019] 2, a second outer antenna element 19, a second inner antenna element 20, and a feed coupling portion 18 are formed on the rear surface 1B of the insulating substrate 1. The second outer antenna element 19 and the second inner antenna element 20 are formed in the shape of semicircular arcs with different radii centered on the same center point O.

[0020] The second outer antenna element 19 is arranged on an arc of the same radius as the first outer antenna element 2 formed on the surface 1A of the insulating substrate 1. The first outer antenna element 2 and the second outer antenna element 19 are perfectly circular in plan view, and the first through-hole 15 is connected to an end of the second outer antenna element 19.

[0021] The second inner antenna element 20 is disposed inside the second outer antenna element 19 at a distance, and the arc length of the second inner antenna element 20 is set to be sufficiently longer than the arc length of the second outer antenna element 19. The second inner antenna element 20 is disposed on an arc having the same radius as the first inner antenna element 3 formed on the surface 1A of the insulating substrate 1. The first inner antenna element 3 and the second inner antenna element 20 form a perfect circle in a plan view, and the second through hole 14 and the third through hole 16 are connected to the end side of the second inner antenna element 20.

[0022] The feed coupling section 18 has an outer feed coupling element 21 and an inner feed coupling element 22 arranged around a center point O. The outer feed coupling element 21 and the inner feed coupling element 22 are spaced apart and formed into an elliptical shape. The outer feed coupling element 21 and the inner feed coupling element 22 each have a gap 24 separating them, and the feed coupling section 18 is arranged in a position that is 180 degrees inverted in plan view from the antenna-side coupling section 17 formed on the surface 1A of the insulating substrate 1. That is, the outer feed coupling element 21 and the first coupling element 7 overlap with each other in an inverted position, and the inner feed coupling element 22 and the third coupling element 9 overlap with each other in an inverted position. Furthermore, feed points 25 and 26 are formed at both ends of the feed coupling elements 21 and 22 separated by the gap 24, respectively. As will be described later, the center conductor and outer conductor of a signal cable (coaxial cable) are selectively connected to these feed points 25 and 26.

[0023] 3, when the antenna patterns formed on the front surface 1A and the back surface 1B of the insulating substrate 1 are seen in a plan view from above, the first outer antenna element 2 and the second outer antenna element 19 are arranged in a perfect circle. In this embodiment, the lengths of the first outer antenna element 2 and the second outer antenna element 19 are adjusted so that the phase rotates 360 degrees on the arc of the circle, and are adjusted to a length corresponding to frequencies in the 2.4 GHz band. One end of the first outer antenna element 2 is connected to the first coupling element 7 via the first connection line 4, and is further connected to one end of the second outer antenna element 19 via the first connection line 10 and the first through-hole 15, thereby forming a first dipole-type circularly polarized antenna compatible with the 2.4 GHz band.

[0024] Similarly, the first inner antenna element 3 and the second inner antenna element 20 are also arranged in a perfect circle. The second inner antenna element 20 has an overlapping portion 20a that overlaps a portion of the first inner antenna element 3 in a planar manner, and this overlapping portion 20a extends the total length of the first inner antenna element 3 and the second inner antenna element 20. In this embodiment, the length is adjusted so that the phase rotates 360 degrees on the arc of the second inner antenna element 20 including the arc length of the first inner antenna element 3 and the overlapping portion 20a, and is adjusted to a length corresponding to frequencies in the 5 GHz band. One end of the first inner antenna element 3 is connected to the second coupling element 8 via the second connection line 5, and is further connected to the vicinity of one end of the second inner antenna element 20 via the second connection line 11 and the second through hole 14, thereby configuring a second dipole-type circularly polarized antenna compatible with the 5 GHz band.

[0025] Furthermore, the third connection line 6 is connected to the third coupling element 9, and the third connection line 12 connected to the third coupling element 9 is connected to the overlapping portion 20a of the second inner antenna element 20 via the third through hole 16, thereby achieving a broadband of the second dipole-type circularly polarized antenna.

[0026] Furthermore, because the antenna-side coupling portion 17 and the feed coupling portion 18 are arranged on both the front and back sides of the insulating substrate 1, facing each other and oriented 180 degrees apart in plan view, the antenna-side coupling portion 17 and the feed coupling portion 18 are capacitively coupled, and gains due to the radio waves of each frequency received by the first dipole circularly polarized antenna and the second dipole circularly polarized antenna are generated in the feed coupling portion 18. By connecting a signal cable to the two feed points 25, 26 of the feed coupling portion 18, the gains of the first and second dipole circularly polarized antennas are combined, and at the same time, the impedance is matched to 50 Ω, resulting in combined gain from the signal cable. In this case, by changing the connection configuration of the center conductor and outer conductor of the signal cable to the two feed points 25, 26 of the feed coupling portion 18, the first and second dipole circularly polarized antennas can be operated as either right-handed or left-handed circularly polarized antennas.

[0027] That is, as shown in Fig. 4, when the center conductor of signal cable (coaxial cable) 29 is connected to feed point 25 on the left side of the figure and the outer conductor serving as the GND line is connected to feed point 26 on the right side of the figure, the gain of a right-handed circularly polarized antenna is obtained from signal cable 29. Conversely, as shown in Fig. 5, when the outer conductor (GND line) of signal cable 29 is connected to feed point 25 on the left side of the figure and the center conductor is connected to feed point 26 on the right side of the figure, the gain of a left-handed circularly polarized antenna is obtained from signal cable 29.

[0028] Next, the operation of the antenna device according to this embodiment will be described with reference to FIGS.

[0029] Figure 6 is an explanatory diagram showing the state in which the right-handed circularly polarized antenna W1 shown in Figure 4 and the left-handed circularly polarized antenna W2 shown in Figure 5 are arranged close to insulating substrate 30. As shown in Figure 6, the right-handed circularly polarized antenna W1 and the left-handed circularly polarized antenna W2 both have dimensions of 34 x 34 mm and are arranged close to insulating substrate 30 with the distance between their respective antenna patterns being 6 mm (3 x 2 mm).

[0030] Fig. 7 is a graph showing the standing wave ratio (VSWR value) of two antennas W1 and W2 when the surface of insulating substrate 30 shown in Fig. 6 is attached to the back side of a case lid made of polycarbonate resin with a thickness of 2 mm, with the horizontal axis representing frequency and the vertical axis representing VSWR value. As shown in Fig. 7, when two antennas W1 and W2 are arranged with the dimensions shown in Fig. 6, the VSWR values ​​in both the 2.4 GHz band and the 5 GHz band can be kept below 2.

[0031] Figure 8 is a graph showing the isolation between the two antennas W1 and W2. As shown in Figure 8, when the two antennas W1 and W2 are arranged with the dimensions shown in Figure 6, the isolation in both the 2.4 GHz band and the 5 GHz band can be made 20 dB or more.

[0032] Figure 9 is a graph showing the maximum and average gain values ​​of two antennas W1 and W2 in the 2.4 GHz and 5 GHz bands, with the horizontal axis representing frequency and the vertical axis representing circularly polarized gain. As shown in Figure 9, when the two antennas W1 and W2 are arranged with the dimensions shown in Figure 6, there is little variation in the gains in the 2.4 GHz and 5 GHz bands, and it can be seen that a stable gain is ensured overall.

[0033] As described above, in the antenna device according to this embodiment, the first outer antenna element 2 and the second outer antenna element 19 corresponding to frequencies in the 2.4 GHz band are formed separately on both the front and back surfaces of the insulating substrate 1, and the first inner antenna element 3 and the second inner antenna element 20 corresponding to frequencies in the 5 GHz band are formed separately on both the front and back surfaces of the insulating substrate 1, and these two pairs of antenna elements are arranged concentrically around the same center point O. The first outer antenna element 2 and the second outer antenna element 19 are joined to the antenna-side coupling part 17 via connection lines 4, 10 and a first through-hole 15, and the first inner antenna element 3 and the second inner antenna element 20 are joined to the antenna-side coupling part 17 via other connection lines 5, 11 and a second through-hole 14. By routing the connection lines 4, 5, 6, 10, 11, and 12 on the insulating substrate 1 without crossing each other, two dipole-type circularly polarized antennas are formed having antenna elements that are nearly perfect circles with no phase difference.

[0034] Furthermore, because the antenna-side coupling portion 17 and the feed coupling portion 18 are arranged on both the front and back surfaces of the insulating substrate 1 facing each other and oriented 180 degrees apart in plan view, the antenna-side coupling portion 17 and the feed coupling portion 18 are capacitively coupled, causing the gains of the first and second circularly polarized antennas to be generated in the feed coupling portion 18. By connecting a signal cable 29 to the two feed points 25, 26 of the feed coupling portion 18, the gains of the first and second circularly polarized antennas are combined, and at the same time, the impedance is matched to 50 Ω, resulting in a combined gain from the signal cable 29. In this case, by changing the connection configuration of the center conductor and outer conductor of the signal cable 29 to the two feed points 25, 26 of the feed coupling portion 18, the first and second circularly polarized antennas can be operated as either right-handed or left-handed circularly polarized antennas.

[0035] Furthermore, second inner antenna element 20 has overlapping portion 20a that overlaps part of first inner antenna element 3 in a plan view, and elliptical third coupling element 9 having gap 13 is formed in antenna side coupling portion 17, and this third coupling element 9 is connected to overlapping portion 20a from third connection line 12 via third through hole 16. This widens the range in which the arc lengths of first inner antenna element 3 and second inner antenna element 20 can be adjusted, thereby achieving a broadband circularly polarized antenna formed by first inner antenna element 3 and second inner antenna element.

[0036] As described above, the antenna device according to this embodiment is a dipole-type half-wavelength antenna in which the radius of the arc of the arc-shaped antenna element can be adjusted to a length that allows the circular polarization phase of the corresponding frequency to rotate 360 ​​degrees. When the arc-shaped antenna element is short, one semicircular antenna element is disposed on the front side of the insulating substrate, and the other semicircular antenna element is disposed on the back side of the insulating substrate, and these semicircular antenna elements are connected using connection lines and through holes. This allows the length of the left and right semicircular antenna elements to be adjusted without contacting each other, and also enables the antenna to be made smaller.

[0037] Furthermore, if the gain obtained from the signal cable connected to the feed point of the feed coupling is that of a right-handed circularly polarized antenna, reversing the connection of the signal cable to the feed point will result in a left-handed circularly polarized antenna using the same antenna pattern. Furthermore, by making the arc-shaped antenna elements of a right-handed circularly polarized antenna (two paired semicircular arc-shaped antenna elements) nearly perfectly circular, the axial ratio (AR) will be 2 dB or less. Similarly, the axial ratio of a left-handed circularly polarized antenna will also be 2 dB or less. Furthermore, the isolation between right-handed and left-handed circularly polarized waves is 20 dB when AR = 2 dB, based on cross-polarization discrimination (XPD), and 25 dB when AR = 1 dB. Therefore, even if a right-handed circularly polarized antenna and a left-handed circularly polarized antenna constructed in this way are installed closely together using the minimum area, the isolation between the two circularly polarized antennas consisting of multiple antenna elements will be 20 dB or more if the axial ratio of both is controlled to 2 dB or less.

[0038] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiments are preferred examples, but a person skilled in the art can realize various alternatives, modifications, variations, or improvements from the contents disclosed in this specification, and these are included in the technical scope described in the appended claims.

[0039] For example, in the above embodiment, the case where the feed coupling section 18 is configured with two elements, namely, the outer feed coupling element 21 and the inner feed coupling element 22, has been described. However, the outer feed coupling element 21 and the inner feed coupling element 22 may be integrated into one element, or the feed coupling section 18 may be configured with three elements corresponding to the three coupling elements 7, 8, and 9 of the antenna side coupling section 17. [Explanation of symbols]

[0040] 1. Insulating substrate 2 First outer antenna element 3 First inner antenna element 4,10 First connecting line 5,11 Second connecting line 6,12 Third connecting line 7 First coupling element 8 Second coupling element 9 Third coupling element 13. Gap 14 Second through hole 15 First through hole 16 3rd through hole 17 Antenna side coupling part 18 Power supply coupling 19 Second outer antenna element 20 second inner antenna element 20a Overlapped part 21 Outer feed coupling element 22 Inner feed coupling element 24 Gap 25,26 Power supply point 29 Signal Cable W1 Right-hand circularly polarized antenna W2 Left-handed circularly polarized antenna

Claims

1. An antenna device in which two dipole circularly polarized antennas corresponding to different frequency bands are arranged on the same insulating substrate, a first outer antenna element and a first inner antenna element formed on one surface of the insulating substrate in semicircular arc shapes with different radii and a common center point; a second outer antenna element and a second inner antenna element formed on the other surface of the insulating substrate in semicircular arc shapes with different radii and a common center point; a first connection line formed on the one surface of the insulating substrate, the first connection line connecting the first outer antenna element and the second outer antenna element via a through hole provided in the insulating substrate; a second connection line formed on the one surface of the insulating substrate and connecting the first inner antenna element and the second inner antenna element via a through hole provided in the insulating substrate; a coupling portion formed on the one surface of the insulating substrate so that the first connection line and the second connection line are coupled to each other; a power supply coupling portion formed on the other surface of the insulating substrate so as to face the coupling portion; Equipped with the first outer antenna element and the second outer antenna element are arranged on the same arc so as to be continuous in a circular ring shape in a plan view, the first inner antenna element and the second inner antenna element are arranged on the same arc so as to be continuous in a circular ring shape in a plan view, the coupling portion has a first coupling element to which the first connection line is connected and a second coupling element to which the second connection line is connected; the first coupling element and the second coupling element are each formed in an elliptical shape with a portion separated, the second coupling element is disposed inside the first coupling element at a distance, an overlapping portion is formed in the second inner antenna element and overlaps with a part of the first inner antenna element in a plan view, an elliptical third coupling element having a dividing portion is disposed inside the second coupling element at a distance, and a third connection line joined to the third coupling element is connected to the overlapping portion via a through hole provided in the insulating substrate; An antenna device characterized by:

2. An antenna device as described in claim 1, wherein the power supply coupling portion is arranged in a position that is 180 degrees inverted from the coupling portion in a planar view.

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