Antenna device

Abstract

To provide an antenna which is small-sized and has a high degree of freedom in design and can cover an ultra-wide band.SOLUTION: An antenna operating from a first frequency to a second frequency, the antenna comprising a first radiating element, a second radiating element, a ground, and a feed portion, wherein the ground is at least coplanar with the first radiating element, and the first radiating element is a planar conductor and comprises a first contact point and a second contact point in contact with the second radiating element, the second radiation element is a linear conductor branching from the feeding portion and has a first region from the first contact point to the feeding portion and a second region from the feeding portion to the second contact point, each of the first region and the second region is shorter than a quarter wavelength of the first frequency, and a separation distance between the ground and the first radiation element on the same plane is shorter than the quarter wavelength of the first frequency.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antenna device, and more particularly to an antenna device for ultra-wideband communications such as UWB (Ultra-Wide Band). [Background technology]

[0002] In recent years, there has been growing interest in UWB (Ultra-Wide Band) communication systems, which utilize extremely wide bandwidths for large-capacity data transmission, high-speed communication, location tracking, security measures, and other applications. Accordingly, antennas capable of covering ultra-wideband frequencies are essential. Antennas operate primarily through resonance, and the resonant structure of an antenna primarily depends on wavelength, so the antenna size must be large to cover a wide frequency band.

[0003] Conventionally, antennas such as those disclosed in Patent Documents 1 and 2 are known as ultra-wideband antennas for use in UWB. Patent Document 1 discloses an ultra-wideband antenna device that covers the frequency bands used by UWB and mobile phones. It is composed of an antenna consisting of a folded plate-like monopole antenna unit with a U-shaped cross section and two conductive elements extending from two points on the folded plate-like monopole antenna. Patent Document 2 discloses a configuration that has the characteristics of both a plate antenna and a loop antenna by switching between them, and can cover a wide band from 0.85 GHz to 6 GHz. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2009-81590 [Patent Document 2] Patent Publication No. 2012-129598 Summary of the Invention [Problem to be solved by the invention]

[0005] The antennas described in Patent Documents 1 and 2 have a three-dimensional structure and are configured using external circuits such as switches in order to cover an ultra-wideband, which leads to problems such as the antenna device becoming more complex and larger in size, and having less design freedom.

[0006] The present invention aims to provide an antenna that is simple, compact, and has a high degree of design freedom and can cover an ultra-wideband by combining two radiating elements on a plane. [Means for solving the problem]

[0007] One aspect of the present invention is an antenna that operates between a first frequency and a second frequency, the antenna comprising a first radiating element, a second radiating element, a ground, and a feed portion, the ground being on at least the same plane as the first radiating element, the first radiating element being a planar conductor having first and second contact points that come into contact with the second radiating element, the second radiating element being a linear conductor branching off from the feed portion and having a first region from the first contact point to the feed portion and a second region from the feed portion to the second contact point, the first region and the second region each being shorter than a quarter wavelength of the first frequency, and the separation distance between the ground and the first radiating element in the same plane being shorter than a quarter wavelength of the first frequency. [Effects of the Invention]

[0008] According to the present invention, it is possible to realize an antenna that is simple, small, and has a high degree of freedom in design and covers an ultra-wide band. [Brief explanation of the drawings]

[0009] [Figure 1] 1A and 1B are diagrams illustrating the overall configuration of an antenna according to a first embodiment; [Figure 2] 1. Antenna configuration examples according to the first embodiment (a, b, c, d) [Figure 3] Electromagnetic field simulation results of the antenna according to the first embodiment [Figure 4]Array arrangement example of antenna according to the first embodiment [Figure 5] 10A and 10B are diagrams showing the overall configuration of an antenna according to a second embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the configurations shown in the following embodiments are merely examples, and the present invention is not limited to the configurations shown in the drawings.

[0011] First Embodiment 1A and 1B are diagrams showing the overall configuration of an antenna according to this embodiment, with Fig. 1B being a cross-sectional view of the YZ plane taken along dashed line AA' in Fig. 1A.

[0012] The antenna comprises a first radiating element 101, a second radiating element 102, a ground 103, a dielectric 104, and a feeding portion 105, and resonates between 3.1 GHz and 10.6 GHz.

[0013] First radiating element 101 and second radiating element 102 are placed on dielectric 104, and ground 103 is placed on the same plane. In addition, power feeding part 105 is connected to second radiating element 102, and the ground of power feeding part 105 is connected to ground 103.

[0014] The first radiating element 101 and the second radiating element 102 are in contact with each other in the first region 106 and the second region 107. With the above configuration, the second radiating element 102 branches into two from the feeding part 105, forming a hollow region and forming a U-shaped element shape.

[0015] The first radiating element 101 operates as a wideband elliptical monopole antenna using the second radiating element 102 as a feeder. The second radiating element 102 shares a portion of the first radiating element 101, and operates like a wideband elliptical loop antenna.

[0016] The combination of these two different antenna behaviors allows the antenna to achieve ultra-wideband operation. Furthermore, it can achieve nearly omnidirectional radiation characteristics at any frequency. This is an advantageous characteristic for so-called UWB tags, which have functions such as positioning.

[0017] This combination also increases the degree of freedom in design. In the first radiating element 101, the resonant frequency changes depending on the length of the major and minor axes of the ellipse. In the second radiating element 102, the characteristic impedance changes depending on its line width, and the resonant frequency changes depending on changes in shape, such as increasing the hollow area in the U-shaped portion. This abundance of design parameters allows for a high degree of freedom in antenna design to match the board and mounting housing.

[0018] Unless otherwise specified in this embodiment, the dielectric is 1 mm thick FR4-epoxy, the radiating element is a 35 μm thick conductor, and the antenna is constructed on a dielectric substrate. The first radiating element 101 is an elliptical element with a major axis in the X-axis direction of FIG. 1(A) of 11.5 mm and a minor axis in the Y-axis direction of FIG. 1(A) of 7.5 mm. The second radiating element 102 is a U-shaped element with a total length of 8 mm and a line width of 0.8 mm. The separation distance between the first radiating element 101 and the ground 103 is 2.5 mm.

[0019] The dimensions can be freely changed to match the desired resonant frequency. For example, the distance between the first radiating element 101 and the ground 103 on the same plane needs to be shorter than a quarter wavelength of the lowest resonant frequency (3.1 GHz in this embodiment) to ensure operation as a wideband elliptical monopole antenna. This is because the antenna obtains wideband characteristics through electrical coupling between the first radiating element 101 and the ground 103. Furthermore, the lengths of the first region 106 and the second region 107 allow the second radiating element 102 to share a portion of the first radiating element 101, thereby functioning like an elliptical loop antenna. Therefore, the lengths of the first region 106 and the second region 107 need only be shorter than a quarter wavelength of the lowest resonant frequency (3.1 GHz in this embodiment). This is because the longer the overall length of the first region 106 and the second region 107, the more the shared shape with the first radiating element 101 becomes distorted, resulting in the loss of the wideband characteristics of the elliptical loop antenna and the loss of the antenna's ultra-wideband characteristics. The lengths of the first region 106 and the second region 107 may be approximately the same or different. A phase difference can be generated by varying the lengths of the first region 106 and the second region 107. For example, the first radiating element 101 may be designed to radiate circularly polarized waves by setting the phase difference between the lengths of the first region 106 and the second region 107 to 90 degrees. However, if the phase difference between these two points were 180 degrees, the signals input from each contact point on the first radiating element 101 would cancel each other out, preventing the antenna from functioning properly. Furthermore, the phase difference at each contact point can be adjusted by setting the lengths of the first region 106 and the second region 107 to different values. The imaginary lines connecting the respective contact points of the antenna shown in FIG. 1 with the ground are substantially parallel, but this can be achieved by moving one of the contact points so that this line is no longer parallel.

[0020] By designing using the above parameters, it is possible to realize an ultra-wideband antenna with a simple and compact configuration and high design freedom.

[0021] FIG. 2 shows an example of shape variations of the first radiating element 101 and the second radiating element 102 in this embodiment. In this embodiment, the first radiating element 101 is described as an elliptical patch type, and the second radiating element 102 is described as a U-shaped type. However, the first radiating element 101 is not limited to an elliptical patch type, and may be any planar shape that can achieve wideband characteristics, such as a polygon ( FIG. 2(A) ), a diamond ( FIG. 2(B) ), a cone (not shown), or a perfect circle (not shown). Similarly, the second radiating element 102 may be a linear shape, such as a U-shape ( FIG. 2(C) ) or a trapezoid ( FIG. 2(D) ), in which the first region 106 and the second region 107 are in contact with each other to form a hollow region. Using these shapes, an ultra-wideband antenna can be realized by performing the design described above, satisfying the separation distance between the first radiating element 101 and the ground 103 and the phase difference at each contact point between the first region 106 and the second region 107.

[0022] Figure 3 shows the results of an electromagnetic field simulation of the antenna in Figure 1. The vertical axis represents the reflection characteristic S11 in dB. The horizontal axis represents frequency in GHz. The UWB frequency band allocated by the FCC (Federal Communication Commission) is 3.1 GHz to 10.6 GHz. In this embodiment, an S11 of -6 dB or less is obtained in this frequency band. In other words, in the wide band of 3.1 GHz to 10.6 GHz, 75% or more of the input power is input to the antenna without reflection, achieving a highly efficient antenna.

[0023] These characteristics confirm that the antenna can be used as an antenna that complies with the IEEE (Institute of Electrical and Electronic Engineers) 802.15.4z standard, for example.

[0024] FIG. 4 shows an example of an array antenna using the antenna of this embodiment.

[0025] The array antenna is configured by arranging multiple antenna elements 201 of this embodiment in the horizontal direction (X direction), and providing a power feed section 105 for each antenna element 201. In FIG. 4, signals are input directly to the antenna elements 201 from the power feed section 105, but it is also possible to configure a power feed line (not shown) and input signals to each antenna element 201. In this case, it is necessary to design the power feed line so that it is spaced apart so as not to affect the antenna radiation. When signals are input in phase, the directivity in the front direction (Z direction) is strong. Furthermore, by providing a phase difference to the signals input to each antenna element 201, it is possible to obtain directivity in directions other than the front direction.

[0026] An important parameter in constructing an array is the spacing between antenna elements. In the case of an omnidirectional antenna array with in-phase feeding, the maximum directional gain can be obtained by setting the element spacing to approximately 0.6 wavelengths or more and 0.8 wavelengths or less at the frequency (3.1 GHz to 10.6 GHz) at which the antenna operates. The element spacing here refers to the distance between the two feed points 105 in FIG. 4. When arraying using the antenna elements of this embodiment, an effective array antenna can be constructed by similar design.

[0027] Furthermore, in order to reduce the correlation coefficient between antennas, it is possible to configure the array antenna to improve its performance by using a method such as providing a slit in the ground 103 (not shown) or by rotating each of the placed antennas 201. Such an array antenna can be used as an antenna for a distance and angle positioning system using UWB, such as ToF (Time of Flight) or AoA (Angle of Arrival), which requires multiple antennas.

[0028] Second Embodiment Figures 5(A) and 5(B) are diagrams showing the overall configuration of the antenna according to this embodiment, and Figure 5(B) is a cross-sectional view of the YZ plane taken along dashed line AA' in Figure 5(A).

[0029] The antenna comprises a first radiating element 101, a second radiating element 102, a ground 103, a dielectric 104, and a feed portion 105, and resonates between 3.1 GHz and 10.6 GHz. The first radiating element 101 is disposed on the dielectric 104, and the ground 103 is disposed on the same plane. The second radiating element 102 is disposed on the opposite side of the dielectric 104 to the first radiating element 101. The feed portion 105 is connected to the second radiating element 102, and the ground of the feed portion 105 is connected to the ground 103. The second radiating element 102 is connected to the first region 106 and the second region 107 through vias 301, and is also connected to the first radiating element 101.

[0030] In this embodiment, a first radiating element 101 and a second radiating element 102 are arranged on both sides of a substrate made of a dielectric material 104, and are connected by a via 301. However, it operates in the same way as the first embodiment, and an ultra-wideband antenna can be realized.

[0031] Unless otherwise specified in this embodiment, the dielectric is 1 mm thick FR4-epoxy, the radiating element is a 35 μm thick conductor, and the antenna is constructed on a dielectric substrate. The first radiating element 101 is an elliptical element with a major axis of 11.5 mm and a minor axis of 7.5 mm. The second radiating element 102 is a U-shaped element with a total length of 8 mm and a line width of 0.8 mm. The distance between the first radiating element 101 and the ground 103 is 2.5 mm. The via 301 is cylindrical with a diameter of 0.8 mm and a height of 1 mm.

[0032] By connecting the first region 106 and the second region 107 with the via 301, the electrical length between the first region 106 and the second region 107 is longer than in the first embodiment described above. Therefore, in this embodiment, even if the first radiating element 101 and the second radiating element 102 are the same size as in the first embodiment, the band on the low side of the resonant frequency is wider. As described above, the resonant structure of the antenna mainly depends on the wavelength, so the antenna size becomes larger to cover a wide frequency band. Therefore, by using the via 301 to increase the electrical length between the first region 106 and the second region 107, it is possible to obtain wider band antenna characteristics with a smaller antenna area.

[0033] Furthermore, when mounting the antenna on a housing, it is conceivable that metal parts, a resin housing, or the human body may come into close proximity to the first radiating element 101. If these are in close proximity, concerns arise regarding the antenna characteristics and the effects of electromagnetic waves on the human body. However, by placing only the first radiating element 101 on the back surface of the dielectric 104 substrate via via 301, the first radiating element 101 can be kept away from metal parts, resin, the human body, etc. Therefore, if the SAR (Specific Absorption Rate) characteristics or antenna characteristics are affected by these factors, improvements in the characteristics can be expected.

[0034] The disclosure of this embodiment includes the following configuration.

[0035] (Item 1) 1. An antenna operating at a first frequency to a second frequency, comprising: the antenna comprises a first radiating element, a second radiating element, a ground, and a feeding portion; the ground is coplanar with at least the first radiating element; the first radiating element is a planar conductor and has first and second contact points that contact the second radiating element; the second radiating element is a linear conductor branching off from the feed portion, and has a first region from the first contact point to the feed portion and a second region from the feed portion to the second contact point, the first region and the second region are each shorter than a quarter wavelength of the first frequency, and a separation distance between the ground and the first radiating element in the same plane is shorter than a quarter wavelength of the first frequency.

[0036] (Item 2) 2. The antenna according to item 1, wherein the first region and the second region have substantially the same length.

[0037] (Item 3) 3. The antenna according to item 1 or 2, wherein the first radiating element is elliptical.

[0038] (Item 4) The antenna described in any one of items 1 to 3, characterized in that the antenna further comprises a dielectric substrate, and the ground and the first radiating element are provided on a first layer of the dielectric substrate.

[0039] (Item 5) 5. The antenna according to item 4, characterized in that the second radiating element and the feeding portion are provided on a second layer different from the first layer, and at least a portion of the first region or the second region includes a via that penetrates the dielectric substrate.

[0040] (Item 6) 6. The antenna according to any one of items 1 to 5, wherein the phase difference between the lengths of the first region and the second region is 90 degrees.

[0041] (Item 7) 7. The antenna according to any one of items 1 to 6, characterized in that it is used in UWB (Ultra Wide Band).

[0042] (Item 8) 8. The antenna according to any one of items 1 to 7, wherein the first frequency is 3.1 GHz and the second frequency is 10.6 GHz.

[0043] (Item 9) An array antenna operating at a first frequency to a second frequency, the array antenna includes a plurality of first radiating elements, a plurality of second radiating elements, a ground, and at least one feeding portion; the ground is coplanar with at least the plurality of first radiating elements; the plurality of first radiating elements are planar conductors and have first and second contact points that contact one second radiating element of the plurality of second radiating elements; the second radiating element is a linear conductor branching off from the feed portion, and has a first region from the first contact point to the feed portion and a second region from the feed portion to the second contact point, the first region and the second region are each shorter than a quarter wavelength of the first frequency, and a separation distance between the ground and the first radiating element in the same plane is shorter than a quarter wavelength of the first frequency.

[0044] (Item 10) 10. The array antenna according to item 9, comprising a plurality of the feed units, wherein the distance between the plurality of feed units is 0.6 wavelengths or more and 0.8 wavelengths or less of a frequency between the first frequency and the second frequency. [Explanation of symbols]

[0045] 101 First radiating element 102 Second Radiating Element 103 Grand 104 Dielectric 105 Power supply unit 106 First Realm 107 Second Realm 201 Antenna element shown in Figure 1 301 Beer

Claims

1. 1. An antenna operating at a first frequency to a second frequency, comprising: the antenna comprises a first radiating element, a second radiating element, a ground, and a feeding portion; the ground is coplanar with at least the first radiating element; the first radiating element is a planar conductor and has first and second contact points that contact the second radiating element; the second radiating element is a linear conductor branching off from the feed portion, and has a first region from the first contact point to the feed portion and a second region from the feed portion to the second contact point, the first region and the second region are each shorter than a quarter wavelength of the first frequency, and a separation distance between the ground and the first radiating element in the same plane is shorter than a quarter wavelength of the first frequency.

2. 2. The antenna according to claim 1, wherein the first region and the second region have substantially the same length.

3. 2. The antenna of claim 1, wherein said first radiating element is elliptical.

4. 2. The antenna according to claim 1, further comprising a dielectric substrate, the ground and the first radiating element being provided on a first layer of the dielectric substrate.

5. The antenna according to claim 4, characterized in that the second radiating element and the feeding portion are provided on a second layer different from the first layer, and at least a portion of the first region or the second region includes a via penetrating the dielectric substrate.

6. 2. The antenna according to claim 1, wherein the phase difference between the lengths of the first region and the second region is 90 degrees.

7. 2. The antenna according to claim 1, wherein the antenna is used in UWB (Ultra Wide Band).

8. 2. The antenna of claim 1, wherein the first frequency is 3.1 GHz and the second frequency is 10.6 GHz.

9. An array antenna operating at a first frequency to a second frequency, the array antenna includes a plurality of first radiating elements, a plurality of second radiating elements, a ground, and at least one feeding portion; the ground is coplanar with at least the plurality of first radiating elements; the plurality of first radiating elements are planar conductors and have first and second contact points that contact one second radiating element of the plurality of second radiating elements; the second radiating element is a linear conductor branching off from the feed portion, and has a first region from the first contact point to the feed portion and a second region from the feed portion to the second contact point, the first region and the second region are each shorter than a quarter wavelength of the first frequency, and a separation distance between the ground and the first radiating element in the same plane is shorter than a quarter wavelength of the first frequency.

10. 10. The array antenna according to claim 9, comprising a plurality of the feed points, wherein a distance between the plurality of feed points is equal to or greater than 0.6 wavelengths and equal to or less than 0.8 wavelengths of a frequency between the first frequency and the second frequency.

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