Antenna device and rectenna device using same

Abstract

To provide an antenna device and a rectenna device including the same capable of improving the rectification efficiency of a rectenna and that are effective for miniaturization and arraying.SOLUTION: An antenna device is configured by: a loop-like element; and a linear element arranged on the loop-like element via a predetermined gap in a vertical direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high-impedance antenna device suitable for improving the rectification efficiency of a rectenna, and to a rectenna device using the same. [Background technology]

[0002] A rectenna has the function of receiving high-frequency radio waves with an antenna and converting them into DC power with a rectifier circuit. In recent years, wireless power transmission, which can wirelessly supply power to mobile devices and mobile terminals such as unmanned aerial vehicles (UAVs) and smartphones, has become widespread. In that case, it is required to be small and highly efficient. In order to improve the rectification efficiency of the rectenna, it is necessary to increase the impedance of the antenna. Furthermore, in order to obtain high output power corresponding to the power required for mobile devices and mobile terminals, it is also required to form antenna devices into arrays.

[0003] Figure 4 of Non-Patent Document 1 discloses a technology in the field of RFID (Radio Frequency Identification) in which a wire-shaped element is coupled to a loop-shaped element as a parasitic element. However, this technology arranges the loop-shaped element and the wire-shaped element on the same plane. [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Gaetano Marrocco, The Art of UHF RFID Antenna Design:Impedance-Matchingand Size-Reduction Techniques, 68 IEEE Antennas and Propagation Magazine, Vol. 50, No. 1, February 2008 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide an antenna device that is effective for improving the rectification efficiency of a rectenna, miniaturizing it, and forming it into an array, and a rectenna device using the same. [Means for solving the problem]

[0006] The antenna device according to the present invention is characterized by comprising a loop element and a linear element disposed above and below the loop element with a predetermined gap therebetween. The expression "through a predetermined gap in the vertical direction" is intended to exclude those arranged on the same plane as disclosed in Non-Patent Document 1, and is not limited to the vertical direction in the literal sense as long as they are arranged so that they partially overlap each other.

[0007] By configuring the antenna in this way, for example, the linear element can be made to resonate in series as a radiating element of about 0.5 wavelength, and the loop element can be made to resonate in parallel as a driving element. Z If quasi-millimeter waves such as these are considered, miniaturization and on-chip implementation will become possible. In addition, in the present invention, when viewed from the linear element side toward the loop element, the linear element is located at the outer periphery of the loop element or inside thereof.

[0008] As will be described in more detail later, even if a loop element alone has high impedance, it does not provide sufficient antenna characteristics in the 28 GHz band. However, by coupling a linear element to the loop element as a parasitic element, it is possible to achieve a wide bandwidth with high impedance.

[0009] In the present invention, the loop element may be formed in a loop shape as a whole, and examples thereof include rectangular, polygonal, circular, and elliptical shapes. In addition, in the present invention, a linear element acts as a parasitic element on a loop element via a predetermined gap, and may be not only straight, but also have a so-called meander shape such as a zigzag shape or a serpentine shape, or a split ring shape with both ends open. Furthermore, a ring-shaped parasitic element may be used as long as it is coupled to a loop-shaped element.

[0010] In the present invention, the gap between the loop element and the linear element increases as the gap becomes larger, and approaches the characteristics of the loop element alone.Therefore, in order to achieve high impedance and wide bandwidth while also achieving miniaturization, the gap is preferably 400 μm or less, although this varies depending on the size of the elements, and is even more preferably in the range of approximately 10 to 400 μm.

[0011] In the antenna device of the present invention, by connecting a rectifier circuit to the loop element, a small, highly efficient rectenna device can be obtained. Furthermore, a plurality of the rectenna devices can be arranged on a substrate to form an array. [Effects of the Invention]

[0012] The antenna according to the present invention is effective in achieving high impedance and has wideband characteristics in the microwave and millimeter wave bands. By using such an antenna, a small rectenna device with high rectification efficiency can be obtained. Furthermore, because it is a small rectenna device, it can be arrayed to produce a high-output rectenna device. [Brief explanation of the drawings]

[0013] [Figure 1] 1A to 1C show an example of the structure of an antenna device according to the present invention, in which (a) is a perspective view, (b) is a plan view, and (c) is a side view. [Figure 2] (a) shows the Smith chart of the loop element coupled with the linear element, and (b) shows the Smith chart of the loop element alone for reference. [Figure 3]The impedance characteristics are shown, with (a) showing an example in which a wire element is coupled to a loop element, and (b) showing the loop element alone for reference. [Figure 4] The graph shows the change in radiation efficiency when the gap between the loop element and the linear element is changed from 100 μm to 400 μm in 50 μm increments. [Figure 5] 1 shows a structural example (embodiment 1) of a rectenna device. [Figure 6] 2 shows a second embodiment of the rectenna device. [Figure 7] 1 shows a third embodiment of the rectenna device. [Figure 8] 4 shows a fourth embodiment of the rectenna device. [Figure 9] 1 shows an example of the structure of an arrayed rectenna device. [Figure 10] 1 shows an example of an arrayed rectenna device having radio wave directionality. [Figure 11] (a), (b), and (c) are shown as application examples of the rectenna device according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] FIG. 1 shows an example of the structure of an antenna device according to the present invention. (a) shows a perspective view, (b) shows a plan view, and (c) shows a side view. A loop element 10 is disposed on the surface of a substrate 1, and a linear element 20 is disposed above the loop element 10 with a predetermined gap G provided therebetween. The loop element 10 has a power supply 11, and when a rectifier circuit is connected to this, it becomes a rectenna device. In the embodiment shown in FIG. 1, the wire element 20 is arranged so as to overlap one side of the loop element 10, but it is sufficient that it is positioned inside the outer shape of the loop element.

[0015] Substrate 1: Dielectric GaAs, size 1.7 × 1.8 × 0.2 mm, εr = 12.9, tan δ = 0.00028 The loop element 10 has an outer diameter of 0.6 × 0.6 mm, a conductor width of 30 μm, and is made of Au. The length of the wire element 20 is 2.6 mm, the wire width is 0.55 mm, and the material is Au. The results of evaluation using an antenna device comprising the above will be described below. FIG. 2(a) shows a Smith chart, and (b) shows the case of the loop element alone for reference. Figure 3(a) shows the impedance characteristics, and (b) shows the case of the loop element alone for reference. Figure 2(a) shows the 28GH Z A kink curve appears near the center of the junction. From Figure 3(a), R is approximately 900 Ω, 28 GH. Z It can be seen that a broad band is observed around FIG. 4 shows the change in gap (G), and it can be seen that when G is 400 μm or more, the characteristics approach those of the loop element alone, so G: 100 to 400 μm is best. Also, in the same figure, the smaller the value of G, the denser the coupling between the loop element and the line element, and the more the radiation efficiency of the antenna improves. In Figure 4, G: 100 μm is the minimum value, but this trend continues even if it is calculated to be 10 μm, resulting in higher efficiency. These results show that the length of the loop element can be reduced to 1 mm or less when the length of the linear element is at the level of 0.5 wavelength.

[0016] FIG. 5 shows an example of a rectenna device (embodiment 1) according to the present invention. In this embodiment, a linear element is formed on a motherboard made of a dielectric material, a loop element and a rectifier circuit are formed on the surface of a semiconductor substrate such as GaAs, GaN, or Si, and the semiconductor substrate is bonded to the motherboard and then bonded to the top of the linear element via multiple protrusions (bumps) to form a gap G. The semiconductor surface on which the rectifier circuit and loop element are formed is bonded to face the linear element. In this way, a small rectenna device using a high impedance antenna according to the present invention can be obtained.

[0017] The structure of the rectenna device can be designed in various forms to suit the actual application. In addition to Example 1 shown in Figure 5, Figure 6 shows Example 2, in which a loop-shaped element is mounted facing upward on the top surface of a semiconductor substrate and is connected to a linear element on a motherboard on the bottom surface of the semiconductor substrate. In FIG. 7, as a third embodiment, an underfill made of a dielectric material may be used between the bumps on the semiconductor substrate and the motherboard to reinforce the bonding strength. FIG. 8 shows a fourth embodiment in which a loop element is formed on the upper surface of a motherboard and a linear element is arranged on the lower surface of the motherboard.

[0018] Figure 9 shows an example of an array formed by placing multiple linear elements on a motherboard and placing loop elements corresponding to each of them. Although FIG. 9 shows an example in which 16 rectennas are arrayed, there is no limit to the number.

[0019] Figure 10 shows an example of how, when arraying a rectenna, the linear elements are made into meander-shaped elements as shown in Figure 11(a), thereby providing radio wave directionality and increasing the antenna gain. In the present invention, the linear element as shown in FIG. 11(b) can be arranged as a split ring-shaped element, or a plurality of loop-shaped elements as shown in (c). In FIG. 11, for the sake of explanation, the loop element and the linear element are shown slightly shifted in the planar direction, but in reality, the linear element and the loop element partially overlap when viewed from a perspective in a planar view. [Explanation of symbols]

[0020] 1 board 10 Loop element 11 Power supply unit 20 Linear element

Claims

1. The loop element is composed of a loop element and a linear element arranged on a different plane with a predetermined gap between them in the vertical direction relative to the loop element, the linear element is arranged to supply power to the loop element in a wireless manner; A rectenna device characterized in that the wire length of the loop element is equal to or less than half the wavelength of the operating frequency, and a rectifier circuit is connected to the loop element.

2. 10. An arrayed rectenna device comprising a plurality of rectenna devices according to claim 1 arranged on a substrate to form an array.

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