Antenna equipment

Abstract

To provide an antenna device that can achieve stable communication between circuit boards while maintaining electrical isolation.SOLUTION: An antenna device includes a first circuit board, a second circuit board arranged to face the first circuit board, a transmitting antenna provided on one of the main surfaces of the first circuit board facing the second circuit board, a reflector provided on one of the main surfaces of the first circuit board opposite to the main surface on which the transmitting antenna is provided, and a receiving antenna provided on one of the main surfaces of the second circuit board facing the first circuit board. The transmitting antenna and the receiving antenna are arranged to face each other between the first circuit board and the second circuit board. The distance between the transmitting antenna and the receiving antenna is equal to or less than 1 / 4 of the wavelength of the radio wave emitted from the transmitting antenna.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The technology disclosed in this specification relates to an antenna device.

Background Art

[0002] Patent Document 1 discloses an example of an antenna device in which an antenna is provided on a circuit board.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There are cases where it is desired to communicate between circuit boards in an electrically insulated state. In such cases, generally, insulating elements such as insulating transformers and photocouplers are used. The inventors of the present invention have considered using an antenna instead of an insulating element. This specification proposes an antenna device capable of realizing stable communication between circuit boards in an electrically insulated state.

Means for Solving the Problems

[0005] One embodiment of an antenna device disclosed herein may include: a first circuit board; a second circuit board disposed opposite to the first circuit board; a transmitting antenna provided on the main surface of the first circuit board that faces the second circuit board; a reflector provided on the main surface of the first circuit board opposite to the main surface on which the transmitting antenna is provided, and the reflector provided opposite to the transmitting antenna; and a receiving antenna provided on the main surface of the second circuit board that faces the first circuit board. The transmitting antenna and the receiving antenna may be disposed opposite to each other between the first circuit board and the second circuit board. The distance between the transmitting antenna and the receiving antenna may be 1 / 4 or less of the wavelength of the radio waves radiated from the transmitting antenna.

[0006] According to the above antenna device, the region between the transmitting antenna and the receiving antenna is generally a near-field region dominated by a quasi-electrostatic field. In short-range communication in the near-field, wave interference is suppressed. Therefore, the transmitting antenna and the receiving antenna are particularly less affected by other surrounding communication antennas, enabling stable communication. Furthermore, the presence of the reflector reduces the resonant frequency due to the increased capacitance component of the transmitting antenna, allowing the transmitting antenna to be made smaller. In addition, the presence of the reflector shields a portion of the electromagnetic field radiated from the transmitting antenna, thereby reducing the influence of electromagnetic field coupling on other surrounding antennas and circuits. As a result, the above antenna device can achieve stable communication between the first circuit board and the second circuit board while electrically insulated, miniaturize the antenna, and suppress electromagnetic field influence on surrounding circuits. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram schematically shows a cross-sectional view of one embodiment of an antenna device. [Figure 2]Figure 1 is a plan view of the first circuit board of the antenna device, wherein the main surface of the first circuit board on which the transmitting antenna is installed is considered the plane. [Figure 3] This diagram schematically shows a cross-sectional view of another embodiment of the antenna device. [Figure 4] Figure 3 is a plan view of the first circuit board of the antenna device, wherein the main surface of the first circuit board on which the transmitting antenna is installed is considered the plane. [Modes for carrying out the invention]

[0008] As shown in Figure 1, the antenna device 1 comprises a first circuit board 10 and a second circuit board 20 housed in a metal casing 30. Such an antenna device 1 is not particularly limited, but may be used, for example, in a circuit system that converts power or voltage.

[0009] Each of the first circuit board 10 and the second circuit board 20 has a flat plate shape and can be made of a substrate of any material. Each of the first circuit board 10 and the second circuit board 20 is not particularly limited, but may be a circuit board made of a composite material of glass fiber and epoxy resin (i.e., FR-4). The thickness of each of the first circuit board 10 and the second circuit board 20 can be set to any thickness. The thickness of each of the first circuit board 10 and the second circuit board 20 is not particularly limited, but may be, for example, 0.8 mm. The first circuit board 10 and the second circuit board 20 are arranged in parallel within the housing 30 and face each other. As will be described in detail later, the first circuit board 10 and the second circuit board 20 may be arranged facing each other with a gap of, for example, several mm to several tens of mm between them. There is an air layer between the first circuit board 10 and the second circuit board 20. Each of the first circuit board 10 and the second circuit board 20 is equipped with various electronic circuits (not shown), and the electronic circuits mounted on the first circuit board 10 and the electronic circuits mounted on the second circuit board 20 are configured to operate at different operating voltages. Therefore, an antenna device 1 is provided to enable secure communication between the electronic circuits of the first circuit board 10 and the electronic circuits of the second circuit board 20.

[0010] As shown in Figures 1 and 2, a transmitting antenna 12 is provided on the main surface of the first circuit board 10 that faces the second circuit board 20. The transmitting antenna 12 is formed by depositing a metal film on the main surface of the first circuit board 10, for example, using printing or etching technology. The transmitting antenna 12 is not particularly limited, but may be formed by depositing a film of copper or aluminum, for example. The transmitting antenna 12 extends from the feed point 12a to which the feed unit 14 is connected to the open end 12b and is composed of a monopole type antenna having a meander pattern. For this reason, a GND plate 16 is provided on the feed point 12a side of the transmitting antenna 12 to exert a mirror image effect. The feed unit 14 is connected to a transmitting circuit (not shown). The transmitting antenna 12 may be composed of a spiral type, loop type, patch type, or dipole type antenna instead of a monopole type antenna. Alternatively, the transmitting antenna 12 may be a chip antenna mounted on the main surface of the first circuit board 10 instead of such a pattern antenna.

[0011] A conductive reflector 18 is provided on the main surface of the first circuit board 10, on the side opposite to the main surface on which the transmitting antenna 12 is mounted. The reflector 18 may be floating or may be connected to a GND plate 16 or a terminal (not shown) (for example, an electrical terminal such as the GND of other antennas or circuits in the vicinity). The reflector 18 is formed by depositing a metal film on the main surface of the first circuit board 10, for example, using printing or etching techniques. The reflector 18 is not particularly limited, but may be formed by depositing a film of copper or aluminum, for example. The reflector 18 is positioned opposite the transmitting antenna 12. More specifically, when the first circuit board 10 is viewed from above, the reflector 18 has a rectangular shape and is positioned to cover the entire area where the transmitting antenna 12 is formed.

[0012] A receiving antenna 22 is provided on the main surface of the second circuit board 20 that faces the first circuit board 10. The receiving antenna 22 may be an antenna with the same structure as the transmitting antenna 12 provided on the first circuit board 10. That is, the receiving antenna 22 may be, for example, a monopole type antenna having a meander pattern, and a GND plate 26 to exert a mirror image effect may be provided on the feed point 12a side of the receiving antenna 22. The receiving antenna 22 may be an antenna with a different structure from the transmitting antenna 12. The transmitting antenna 12 of the first circuit board 10 and the receiving antenna 22 of the second circuit board 20 are arranged to face each other between the first circuit board 10 and the second circuit board 20. The receiving antenna 22 is connected to a receiving circuit (not shown).

[0013] A conductive shielding plate 28 is provided on the main surface of the second circuit board 20 opposite to the main surface on which the receiving antenna 22 is mounted. The shielding plate 28 may be floating or may be connected to a GND plate 26 or a terminal (not shown) (for example, an electrical terminal such as the GND of other antennas or circuits in the vicinity). The shielding plate 28 is formed by depositing a metal film on the main surface of the second circuit board 20, for example, using printing or etching techniques. The shielding plate 28 is not particularly limited, but may be formed by depositing a film of copper or aluminum, for example. The shielding plate 28 is positioned opposite the receiving antenna 22. More specifically, when the second circuit board 20 is viewed from above, the shielding plate 28 has a rectangular shape and is positioned to cover the entire area where the receiving antenna 22 is formed.

[0014] The transmitting antenna 12 on the first circuit board 10 and the receiving antenna 22 on the second circuit board 20 are configured to communicate using radio waves with frequencies on the order of GHz. As described above, the distance between the first circuit board 10 and the second circuit board 20, that is, the distance D1 between the transmitting antenna 12 and the receiving antenna 22, is, for example, a few millimeters to a few tens of millimeters. Specifically, the distance D1 between the transmitting antenna 12 and the receiving antenna 22 is 1 / 4 or less of the wavelength (λ) of the communication radio waves radiated from the transmitting antenna 12, and more preferably λ / (2π) or less.

[0015] When the distance D1 between the transmitting antenna 12 and the receiving antenna 22 is set to such a short distance, the region between the transmitting antenna 12 and the receiving antenna 22 becomes a region of roughly near-field, where a quasi-electrostatic field is dominant. The transmitting antenna 12, being a monopole type, is a radiation source that emits an electric field. Therefore, the transmitting antenna 12 and the receiving antenna 22 can communicate by utilizing the electric field radiated from the transmitting antenna 12.

[0016] In antenna device 1, a reflector 18 is provided corresponding to the transmitting antenna 12. With such a reflector 18 provided, the radiation of radio waves radiated from the transmitting antenna 12 in the direction of the reflector 18 is suppressed from being radiated beyond the reflector 18. As a result, interference and noise components are reduced in communication between the transmitting antenna 12 and the receiving antenna 22.

[0017] On the other hand, radio waves radiated from the transmitting antenna 12 towards the reflector 18 have their phase reversed at the reflector 18 and propagate towards the receiving antenna 22. In the far field, where the distance from the transmitting antenna 12 is great, the phase difference between the radio waves directly radiated from the transmitting antenna 12 and the radio waves reflected by the reflector 18 is approximately 180 degrees, causing wave interference and weakening the radio wave intensity. However, in antenna device 1, the transmitting antenna 12 and the receiving antenna 22 are positioned at a short distance where the near field is dominated by a quasi-electrostatic field. Therefore, no wave interference or null points occur in communication between the transmitting antenna 12 and the receiving antenna 22. Also, because the distance D1 between the transmitting antenna 12 and the receiving antenna 22 is short, the electric field radiated from the transmitting antenna 12 has directionality relative to the receiving antenna 22. Consequently, antenna device 1 can perform stable communication between the electronic circuits of the first circuit board 10 and the electronic circuits of the second circuit board 20 while electrically isolated.

[0018] Furthermore, by setting the distance between the transmitting antenna 12 and the reflector 18, i.e., the thickness of the first circuit board 10, to λ / 4, the phase difference between the radio waves directly radiated from the transmitting antenna 12 and the radio waves reflected by the reflector 18 becomes approximately 360 degrees, which may suppress wave interference in the far field. However, adopting such a configuration would increase the thickness of the first circuit board 10. On the other hand, in antenna device 1, it is not necessary to set the distance between the transmitting antenna 12 and the reflector 18, i.e., the thickness of the first circuit board 10, to λ / 4. The thickness of the first circuit board 10 can be made thinner than λ / 4. For this reason, antenna device 1 has a structure that is advantageous for miniaturization.

[0019] Also, in the antenna device 1, since the reflector 18 is formed larger than the formation range of the transmission antenna 12, the far-field component of the electromagnetic field radiated from the transmission antenna 12 in the direction opposite to the reflector 18 is attenuated, and the near-field component becomes dominant. Therefore, the antenna device 1 has a structure suitable for short-range communication. Even if the reflector 18 is formed smaller than the formation range of the transmission antenna 12, since there is an effect of increasing the capacitance component of the transmission antenna 12, the resonance frequency can be made lower. Also, even if the reflector 18 is formed smaller than the formation range of the transmission antenna 12, since the reflector 18 is connected to the GND, the effect of suppressing the far-field electromagnetic field can be exerted.

[0020] Also, in the antenna device 1, a shielding plate 28 is provided corresponding to the receiving antenna 22. A part of the radio wave radiated spherically from the transmission antenna 12 may pass through between the first circuit board 10 and the second circuit board 20 and propagate, and may be reflected by the inner surface of the housing 30. When the radio wave reflected by the inner surface of the housing 30 enters the receiving antenna 22, it causes interference and noise components. The shielding plate 28 can shield the radio wave reflected by the inner surface of the housing and directed toward the receiving antenna 22. Thereby, the antenna device 1 can perform stable communication.

[0021] In the antenna device 1, the GND plates 16, 26 are provided only on one side of the antennas 12, 22. Instead of this example, the GND plates 16, 26 may be provided so as to surround the antennas 12, 22. It is possible to suppress a part of the radio wave radiated from the transmission antenna 12 from passing through between the first circuit board 10 and the second circuit board 20 and propagating.

[0022] In the above embodiment, one transmission antenna 12 is provided on the first circuit board 10, and one receiving antenna 22 is provided on the second circuit board 20. Instead of this example, as in the antenna device 2 shown in FIGS. 3 and 4, a plurality of transmission antennas NaIt may be provided on the first circuit board 10, and a plurality of receiving antennas 22 shown in FIGS. 1 and 2 are used as one unit. Na It may be provided on the second circuit board 20. In this example, each of the transmitting antenna 12 and the receiving antenna 22 is composed of two units, but it may have more units.

[0023] The plurality of transmitting antennas 12 and the plurality of receiving antennas 22 are arranged such that the combination of the corresponding transmitting antenna 12 and the receiving antenna 22 faces each other between the first circuit board 10 and the second circuit board 20. In the antenna device 2, communication can be independently performed between the combination of the corresponding transmitting antenna 12 and the receiving antenna 22.

[0024] Also, in the antenna device 2, the first GND plate 16 provided on the first circuit board 10 is provided so as to surround each of the plurality of transmitting antennas 12. Similarly, in the antenna device 2, the second GND plate 26 provided on the second circuit board 20 is provided so as to surround each of the plurality of receiving antennas 22.

[0025] The radio waves radiated from one transmitting antenna 12 spread spherically and propagate. Therefore, the radio waves radiated from one transmitting antenna 12 propagate not only toward the corresponding receiving antenna 22 but also toward the adjacent receiving antenna 22. However, in the antenna device 2, the first GND plate 16 is provided between each of the plurality of transmitting antennas 12, and the second GND plate 26 is provided between each of the plurality of receiving antennas 22. Such GND plates 16 and 26 have a function of absorbing radio waves (electromagnetic fields) that propagate toward a receiving antenna 22 that is non-corresponding (that is, adjacent to one receiving antenna 22 that is the communication partner of one transmitting antenna 12) from one transmitting antenna 12. Thereby, in the antenna device 2, interference and noise components can be reduced, so that stable communication can be performed between the combination of the corresponding transmitting antenna 12 and the receiving antenna 22.

[0026] In the above example, the first GND plate 16 was provided on the same plane as the multiple transmitting antennas 12. The portion of the first GND plate 16 that absorbs the (electromagnetic field) directed toward the incompatible receiving antenna 22, that is, the portion of the first GND plate 16 located between adjacent transmitting antennas 12, may be provided on a different plane from the multiple transmitting antennas 12. For example, the portion of the first GND plate 16 located between adjacent transmitting antennas 12 may be embedded in the first circuit board 10, or it may be provided on the main plane opposite to the main plane on which the multiple transmitting antennas 12 are provided. In such a case as well, it can perform the function of absorbing the (electromagnetic field) directed toward the incompatible receiving antenna 22, similar to the above. The same applies to the second GND plate 26; the portion of the second GND plate 26 located between adjacent receiving antennas 22 may be provided on a different plane from the multiple receiving antennas 22.

[0027] The following summarizes the features of the technology disclosed in this specification. Note that each of the technical elements described below is an independent technical element, and exhibits technical usefulness either individually or in various combinations.

[0028] (Feature 1) First circuit board and A second circuit board is positioned opposite the first circuit board, A transmitting antenna is provided on the main surface of the first circuit board that faces the second circuit board, A reflector provided on the main surface of the first circuit board opposite to the main surface on which the transmitting antenna is provided, and positioned opposite the transmitting antenna, The second circuit board includes a receiving antenna provided on the main surface of the second circuit board that faces the first circuit board, The transmitting antenna and the receiving antenna are arranged to face each other between the first circuit board and the second circuit board. An antenna device in which the distance between the transmitting antenna and the receiving antenna is 1 / 4 or less of the wavelength of the radio waves radiated from the transmitting antenna.

[0029] (Feature 2) The antenna device according to feature 1, further comprising a shielding plate provided on the main surface of the second circuit board opposite to the main surface on which the receiving antenna is provided, and positioned to face the receiving antenna.

[0030] (Feature 3) The antenna device according to feature 1 or 2, further comprising a housing for housing the first circuit board and the second circuit board.

[0031] (Feature 4) On the main surface of the first circuit board that faces the second circuit board, The aforementioned transmitting antenna but Separated from each other multiple Placed Teo the law of nature, On the main surface of the second circuit board that faces the first circuit board, The aforementioned receiving antenna but Separated from each other multiple Placed Teo the law of nature, The aforementioned multiple transmitting antennas Na and The aforementioned Multiple receiving antenna Na is , the corresponding transmitting antenna Na and The aforementioned receiving antenna Na The antenna device according to any one of features 1 to 3, wherein the combination is arranged so as to face each other between the first circuit board and the second circuit board.

[0032] (Feature 5) A first GND plate provided on the first circuit board, wherein the plurality of transmitting antennas Na The first GND plate is positioned between each of them, A second GND plate provided on the second circuit board, wherein the plurality of receiving antennas Na The antenna device according to feature 4, further comprising a second GND plate positioned between each of them.

[0033] (Feature 6) The antenna device according to any one of features 1 to 5, wherein the transmitting antenna is a monopole, spiral, loop, patch, or dipole antenna.

[0034] (Feature 7) The antenna device according to feature 1, wherein the reflector is conductive.

[0035] (Feature 8) The antenna device according to feature 7, wherein the reflector is floating or connected to ground.

[0036] (Feature 9) The antenna device according to feature 2, wherein the shielding plate is conductive.

[0037] (Feature 10) The antenna device according to feature 9, wherein the shielding plate is floating or connected to ground.

[0038] Although specific examples of the present invention have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of symbols]

[0039] 1,2: Antenna device, 10: First circuit board, 12: Transmitting antenna, 16: First GND board, 18: Reflector, 20: Second circuit board, 22: Receiving antenna, 26: Second GND board, 28: Shielding plate, 30: Enclosure

Claims

1. First circuit board and A second circuit board is positioned opposite the first circuit board, A plurality of transmitting antennas are provided on the main surface of the first circuit board that faces the second circuit board, and are arranged apart from each other. A reflector provided on the main surface of the first circuit board opposite to the main surface on which the plurality of transmitting antennas are provided, and the reflector is positioned to face the plurality of transmitting antennas, A plurality of receiving antennas are provided on the main surface of the second circuit board that faces the first circuit board, and are arranged apart from each other. A first GND plate provided on the first circuit board, the first GND plate being positioned between each of the plurality of transmitting antennas, The second circuit board includes a second GND board provided on the second circuit board, which is positioned between each of the plurality of receiving antennas, The plurality of transmitting antennas and the plurality of receiving antennas are arranged such that corresponding combinations of the transmitting antennas and receiving antennas face each other between the first circuit board and the second circuit board. An antenna device in which the distance between the transmitting antenna and the receiving antenna is 1 / 4 or less of the wavelength of the radio waves radiated from the transmitting antenna.

2. The antenna device according to claim 1, further comprising a shielding plate provided on the main surface of the second circuit board opposite to the main surface on which the plurality of receiving antennas are provided, the shielding plate being arranged to face the plurality of receiving antennas.

3. The antenna device according to claim 1, further comprising a housing for housing the first circuit board and the second circuit board.

4. The antenna device according to any one of claims 1 to 3, wherein the transmitting antenna is a monopole, spiral, loop, patch, or dipole antenna.

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