Antenna device, antenna built-in device

Abstract

To reduce only SAR while keeping satisfactorily a radiation characteristic of an antenna disposed inside of a housing.SOLUTION: In an antenna device disposed inside of a conductive housing, the housing comprises a first face and a second face, which is opposed with the first face, and at least one opening is provided in a conductor on the first face. The antenna device includes: a first element including a first feeding end and extending in a direction across the first face; and a second element including a first open end, connected with the first element and extending along the first face. The first element and the second element are disposed at positions overlapping the opening in a direction vertical to the first face. In a view in the direction vertical to the first face, a shortest distance from the first open end of the second element to an end portion of the opening is longer than a shortest distance from the first feeding end of the first element to the end portion of the opening.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an antenna device and an antenna-equipped device. [Background technology]

[0002] When installing wireless devices used in close proximity to the human body, human exposure to electromagnetic waves emitted from the wireless device's antenna, i.e., SAR (Specific Absorption Rate), becomes an issue. SAR is proportional to the square of the electric field strength of the electromagnetic waves emitted from the wireless device, and the electric field strength attenuates the further away from the antenna. Therefore, SAR can be reduced by installing the antenna in a recessed position within the housing, away from where the human body is expected to be. However, installing the antenna in a recessed position within the housing can sometimes reduce the antenna's radiation efficiency. For this reason, there is a demand for technology that can reduce SAR without reducing radiation efficiency.

[0003] Patent Document 1 discloses a method of using a housing current suppression means and a parasitic element, and a method of using a part of the housing positioned behind the antenna as a reflector when viewed from the opening, as a configuration for improving the gain, which is the radiation efficiency of the antenna, and reducing the SAR. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-110329 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there are cases where there is not enough space inside the housing to mount the antenna, making it impossible to provide a housing current suppression means and a parasitic element. Similarly, there are cases where the distance from the antenna to the housing is not sufficient, making it impossible to obtain the effect of the reflector. In such cases, it has been difficult to reduce the SAR while maintaining good radiation characteristics of the antenna placed inside the housing. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems, an antenna device according to one aspect of the present invention comprises: An antenna device disposed inside a conductive housing, the housing has a first surface and a second surface opposite to the first surface, the conductor on the first surface has at least one opening; The antenna device includes: a first element including a first feed end and extending in a direction transverse to the first plane; a second element extending along the first surface, the second element having a first open end and a connection with the first element; Including, the first and second elements are disposed at positions overlapping the opening in a direction perpendicular to the first surface; When viewed in a direction perpendicular to the first surface, the shortest distance from the first open end of the second element to the edge of the opening is longer than the shortest distance from the first feeding end of the first element to the edge of the opening. [Effects of the Invention]

[0007] According to the present invention, it is possible to reduce the SAR while maintaining good radiation characteristics of the antenna placed inside the housing. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating the configuration of an antenna-equipped device according to the present embodiment. [Figure 2]A diagram showing the positional relationship between the antenna and the opening in Figure 1. [Figure 3] A diagram showing the SAR distribution of the antenna in Figure 2 [Figure 4] Diagram of a conventional antenna [Figure 5] A diagram showing the SAR distribution of the antenna in Figure 4. [Figure 6] FIG. 10 is a diagram showing a modified example of the antenna-equipped device according to the present embodiment; [Figure 7] FIG. 10 is a diagram showing a modified example of the antenna-equipped device according to the present embodiment; [Figure 8] FIG. 10 is a diagram showing a modified example of the antenna-equipped device according to the present embodiment; [Figure 9] FIG. 10 is a diagram showing a modified example of the antenna-equipped device according to the present embodiment; [Figure 10] FIG. 10 is a diagram showing a modified example of the antenna-equipped device according to the present embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0010] In the following embodiment, a technology is described that can reduce only the SAR while maintaining good radiation characteristics of an antenna placed inside a housing with limited antenna mounting space. Conventionally, methods have been known in which an antenna is mounted in a narrow housing by bending part of the antenna, such as an inverted-F antenna, while suppressing degradation of radiation characteristics such as radiation efficiency. However, when an inverted-F antenna is used, the SAR increases due to changes in the antenna directivity, and it may be necessary to reduce the transmission output. In response to this, this embodiment describes a technology that can adjust the positional relationship between the antenna and the housing, and ultimately the positional relationship between the antenna and the housing, and ultimately the opening provided in the housing, to balance the radiation characteristics and SAR.

[0011] In this embodiment, unless otherwise specified, the dielectric is FR4 (Flame Retardant Type 4) epoxy resin (FR4-epoxy), and the conductor is a 35 μm thick copper thin film or a 1.5 mm thick steel material. The electromagnetic field simulator used to calculate the antenna's reflection characteristics and SAR uses the electrical constants of FR4-epoxy and copper used in general printed circuit boards, and the steel material is defined as a perfect conductor.

[0012] The signal line connected to the antenna for transmitting and receiving high-frequency signals is a thin coaxial cable, and in the figure, one end of the thin coaxial cable is shown as being connected to an AC power source. The thin coaxial cable may be connected to the antenna via an unbalanced-to-balanced converter (not shown), such as a balun, which converts an unbalanced connection to a balanced connection, or it may be connected to the antenna without a balun.

[0013] The phantom, which mimics the human body, is made of a material with electrical constants defined by the IEC. In the graph showing the frequency characteristics of the reflection gain, the horizontal axis represents frequency [GHz] and the vertical axis represents gain [dB], and the SAR distribution diagram shows the SAR value [mW / g] at each position inside the phantom. The materials, material thicknesses, shapes, and other parameters shown here are merely examples, and all parameters that achieve the same effect are included in the embodiments.

[0014] <Embodiment 1> 1 shows a plan view of the housing of an antenna-equipped device equipped with an antenna according to this embodiment, and a cross-sectional view of the housing taken along line a-a' in the plan view. The antenna-equipped device 1 includes a housing 100, a support member 106, an antenna (antenna device) 107, a power supply unit 108, and a substrate 109. The support member 106, the antenna 107, the power supply unit 108, and the substrate 109 are arranged inside the housing 100.

[0015] Housing 100 is a conductive housing composed of conductor 101 on the top surface (first surface), conductor 102 on the bottom surface (second surface) opposite conductor 101, and conductor 103 connecting conductors 101 and 102 around the entire circumference in the thickness direction. In this embodiment, conductors 101 to 103 are all made of steel, and conductors 101 and 102 are 300 mm x 300 mm in plan view, and conductor 103 is 6 mm x 1.5 mm in cross section. Conductor 101 has an opening of 60 mm x 60 mm, and conductor 103 has an opening of 60 mm (depth direction in cross section) x 5 mm, and each opening is covered and sealed with dielectric resin parts 104 and 105.

[0016] Although the housing 100 is shown as having a substantially rectangular parallelepiped shape, it may also have a cylindrical shape in which the conductors 101 and 102 are disk-shaped.

[0017] The support member 106 is a stepped dielectric member, and is a holding portion that is placed on the substrate 109 at a position where the antenna 107 overlaps with the resin portion 104 in a plan view.

[0018] Antenna 107 is a dipole antenna that is attached to support member 106 so that power supply part 108 is perpendicular to resin part 104, and radiates high-frequency signals as electromagnetic waves. The larger the area of ​​the opening where dielectric resin parts 104 and 105 are arranged, the more improved the radiation characteristics of electromagnetic waves from antenna 107 radiated to the outside of antenna-equipped device 1. In one example, each of the four sides of resin part 104 has a length equal to or less than half the wavelength λ of the electromagnetic waves transmitted and received by antenna 107.

[0019] In this embodiment, the space for arranging the antenna 107 is assumed to be equal to or less than ¼ of the wavelength of the electromagnetic waves transmitted and received in the vertical direction. In such cases, there may be no space to arrange a reflector or a parasitic element on the antenna 107. For this reason, in this embodiment, the shape of the antenna 107 and its positional relationship with the resin part 104 are adjusted to reduce the SAR without significantly changing the directivity of the antenna-equipped device 1. In one example, the thickness of the housing 100 in the vertical direction is equal to or less than ¼ of the wavelength of the electromagnetic waves transmitted and received by the antenna 107.

[0020] Substrate 109 is a wireless module on which an electric circuit (not shown) that controls the operation of the housing and mounted components (not shown) are arranged, and serves as a high-frequency signal source that transmits and receives high-frequency signals to be supplied to power supply unit 108. Substrate 109 is fixed to conductor 102, and substrate 109 and power supply unit 108 are connected by a coaxial line. Note that substrate 109 may include a module having a function other than transmitting and receiving high-frequency signals, and may be composed of multiple substrates.

[0021] For example, when the device with built-in antenna 1 is used for digital radiography or the like, the conductor 102 may be the irradiated surface that receives X-rays, and in this case, the substrate 109 includes an image processing circuit for X-rays.

[0022] 2 is an enlarged view of the resin part 104, the support member 106, the antenna 107, and the power supply part 108 in FIG. 2 indicates a part of the conductor 101 which is the top surface of the housing 100, and the substrate 203 indicates a part of the substrate 109. The resin part 104 is arranged so as to seal a rectangular opening provided in the conductor 201, and the substrate 203 is arranged so as to face the resin part 104. The substrate 203 may be a conductor such as another metal plate arranged inside the housing or the bottom surface of the housing.

[0023] The dielectric support member 204 has two surfaces at different heights, horizontal surface 204a and horizontal surface 204c, and further has a vertical surface, vertical surface 204b, connecting horizontal surface 204a and horizontal surface 204c. Support member 204 corresponds to support member 106 in FIG. 1.

[0024] The coaxial cable is composed of a core 205 and an outer sheath 206, and one end of the core 205 is connected to an antenna element (first element) 207, and one end of the outer sheath 206 is connected to an antenna element 208 (third element) on the vertical plane 204b. In the following description, the portions where the core 205 and the outer sheath 206 are connected to the antenna elements 207 and 208, respectively, are referred to as the feeding end. Although not shown in Fig. 2, a balun such as a sleeve balun may be provided near the connection portion of the coaxial cable between the elements 207 and 208.

[0025] Element 207 extends along vertical surface 204b and is connected to element 209 (second element) on horizontal surface 204a, while element 208 extends along vertical surface 204b in the opposite direction to element 207 and is connected to element 210 (fourth element) on horizontal surface 204c. Note that although elements 207 and 208 are shown as extending in opposite directions in the example of Fig. 2, they may extend in different directions.

[0026] Core wire 205 is connected to an RF line (not shown) of substrate 109 through which a high-frequency signal flows, and outer sheath 206 is connected to the ground (not shown) of substrate 109. The combined length of elements 207 and 209 is approximately equal to the combined length of elements 208 and 210, and is close to ¼ of the wavelength λ of the RF signal transmitted and received by the high-frequency signal source. That is, in this embodiment, the combined length of elements 208 and 210 is determined based on a design method for a half-wavelength dipole antenna, and then the element length is adjusted based on the input impedance, etc., thereby determining the dimensions of elements 208 and 210.

[0027] Here, the elements 207 to 210 are described as all being conductors (thin copper film), but they may be coated with a resin material or the like to prevent deterioration of the conductors due to contact with air, or may be provided with an adhesive layer for fixing them to the support member 204. For example, they may be folded and attached along the support member 204 as an FPC (flexible printed circuit) antenna. In other words, the elements 207 to 210 may be made of a plurality of types of materials.

[0028] Furthermore, support member 204 may be arranged so that at least elements 207 and 208 are perpendicular to elements 209 and 210, and may, for example, smoothly connect horizontal surface 204a and horizontal surface 204c. For example, horizontal surface 204a and vertical surface 204b, and vertical surface 204b and horizontal surface 204c may be connected by rounded corners with a curvature radius greater than 0, for example, a curvature radius of 1 mm or more. Even in this case, elements 207 and 208 can be arranged perpendicular to resin part 104, and elements 209 and 210 can be arranged horizontally.

[0029] At this time, resin part 104 is located above support member 204, and when viewed from above in the drawing, the length from the open end of element 209 to the side (end) that is the shortest distance to resin part 104 at the end of the extension is defined as L1. Similarly, the length from the end of element 209 connected to element 207 to the side (end) that is the shortest distance to resin part 104 in the extension direction of element 209 is defined as L2.

[0030] In this embodiment, the relationship L1>L2 is established. Here, the vertical direction viewed from the power feed end is the direction in which the gain of antenna 107 increases. For this reason, in this embodiment, by arranging resin part 104 vertically above the power feed end, L2≧0 is set so as not to obstruct radiation from antenna 107.

[0031] 3 shows the distribution of SAR values ​​in a phantom placed opposite the antenna across the resin part 104, assuming that the height in the vertical direction from the bottom surface of the support member 204 to the horizontal surface 204a is 5 mm and the height from the bottom surface of the support member 204 to the horizontal surface 204c is 1 mm. In FIG. 3, the SAR value distribution shows that the closer to elements 207 and 208 the SAR value becomes, the higher it becomes. At a resonant frequency in the 5 GHz band where S11, which indicates a return loss, is -8 dB and the radiation efficiency is -2 dB, the maximum SAR value when a 1 W high-frequency signal is input is 31.77 mW / g.

[0032] When observed in the near field of antenna 107, i.e., at a location outside housing 100 close to resin part 104, the electric field component parallel to resin part 104, i.e., the horizontal direction, contributes more to SAR than the electric field component in the vertical direction. This is because, on the surface of the human body facing housing 100 at the observation point, the electric field component perpendicular to resin part 104, i.e., the surface of the human body, rapidly attenuates, whereas the parallel electric field component is not sufficiently attenuated and thus acts dominantly on SAR. When elements 207 and 208 are arranged perpendicular to resin part 104, elements 207 and 208 radiate electromagnetic waves in which the electric field component perpendicular to resin part 104 is dominant. As a result, the electric field component parallel to resin part 104 can be attenuated more than when antenna 107 does not have elements 207 and 208, thereby reducing SAR.

[0033] On the other hand, when observed in the far field of the antenna 107, the main beam radiated by the elements 207 to 210, i.e., the maximum radiation direction of the electromagnetic waves, must include the direction penetrating the resin part 104, i.e., the vertical direction. For this reason, the element lengths of the elements 207 and 208 on the vertical surface 204b must each be ⅛ of the wavelength λ or less, and further, the element lengths of the elements 209 and 210 are longer than the element lengths of the elements 207 and 208. In other words, the dimensions of the elements 207 to 210 are determined so that the proportion of the electromagnetic waves radiated from the elements 207 and 208 does not become dominant among the electromagnetic waves radiated from the antenna 107. This makes it possible to reduce the SAR of the antenna-equipped device 1 while maintaining the radiation direction of the electromagnetic waves, for example, in applications such as digital radiography.

[0034] For comparison, a configuration in which a dipole antenna is arranged in an unbent state is shown in Fig. 4. Antenna 107 shown in Fig. 4 does not have an element extending in the vertical direction, but has elements 407 and 408 extending in the horizontal direction.

[0035] Resin part 104 is arranged so as to cover an opening located in conductor 401, which is the top surface of housing 100, and substrate 403 is arranged so as to extend parallel to and face resin part 104. Conductors 401 and 403 are similar to conductors 201 and 203 in Fig. 2, and therefore a description thereof will be omitted.

[0036] The support member 404, which is a dielectric, has a horizontal surface 404a as a horizontal surface. The elements 407 and 408 are arranged so as to extend along the resin part 104.

[0037] The coaxial cable is composed of a core 405 and an outer sheath 406, and one end of the core 405 is connected to an antenna element 407, and one end of the outer sheath 406 is connected to an antenna element 408 on the horizontal plane 404a. As in Fig. 2, a balun such as a sleeve balun may be provided near the connection between the coaxial cable elements 407 and 408. The elements 407 and 408 are conductors (thin copper film), and their element lengths are approximately equal, each being approximately 1 / 4 of the wavelength λ of the RF signal transmitted and received by the high-frequency signal source.

[0038] 5 shows the SAR distribution inside the phantom placed opposite the antenna across the resin part 104, assuming that the height from the bottom surface of the support member 404 to the horizontal surface 404a in the vertical direction is 3 mm. The calculation conditions for the SAR distribution are the same as those for FIG.

[0039] In Fig. 5, the SAR value at an input of 1 W is 32.27 mW / g, which is higher than the SAR shown in Fig. 3. That is, according to the configuration shown in Fig. 2, it is possible to reduce the SAR while maintaining the radiation efficiency of antenna 107, compared to the configuration shown in Fig. 4.

[0040] (Variation 1) 1 to 5, antenna 107 has been described as a dipole antenna designed for a single frequency band, but antenna 107 may be designed to operate in multiple frequency bands. Fig. 6 shows a modified example in which a branched dipole antenna is applied to antenna 107 for operation in multiple frequency bands. This modified example will be described as a two-branched dipole antenna for dual-band operation.

[0041] 6, conductor 601 indicates a part of conductor 101, which is the top surface of housing 100, and substrate 603 is shown, which is a part of substrate 109 arranged so as to face parallel to conductor 601. Like substrates 203 and 403, substrate 603 may be a conductor such as another metal plate arranged inside housing 100 or the bottom surface of housing 100.

[0042] Support member 604, which is a dielectric, has two surfaces at different heights, horizontal surface 604a and horizontal surface 604c, and further has a vertical surface, vertical surface 604b, connecting horizontal surface 604a and horizontal surface 604c. Surfaces 604a to 604c are assumed to be similar to surfaces 204a to 204c.

[0043] The coaxial cable is composed of a core 605 and an outer sheath 606, and one end of the core 605 is connected to an antenna element 607, and one end of the outer sheath 606 is connected to an antenna element 608 on the vertical plane 604b.

[0044] Element 607 extends on vertical surface 604b and is connected on horizontal surface 604a to element 609 and element 610 branching off from 609. Element 608 extends on vertical surface 604b in the opposite direction to element 607 and is connected on horizontal surface 604c to element 611 and element 612 branching off from 611.

[0045] It should be noted that element 609 is longer than element 610, and element 611 is longer than element 612. Elements 607 to 612 are all made of conductors (thin copper film).

[0046] The sum of the lengths of elements 607 and 609 is approximately equal to the sum of the lengths of elements 608 and 611, and is close to λl / 4, where λl is the wavelength of the low-frequency radio signal of the RF signals transmitted and received by each high-frequency signal source. Furthermore, the sum of the lengths of elements 607 and 610 is approximately equal to the sum of the lengths of elements 608 and 612, and is close to λh / 4, where λh is the wavelength of the high-frequency radio signal of the RF signals transmitted and received by each high-frequency signal source.

[0047] As a result, elements 607 and 608 are arranged perpendicular to the resin part 104, and elements 609 to 612 are arranged horizontally to the resin part 104.

[0048] 2, the height from the bottom surface of support member 604 to horizontal surface 604a in the vertical direction is 5 mm, and therefore the element lengths of elements 607 and 608 on vertical surface 604b are each 1 / 8 or less of the wavelength λh on the high-frequency side. Also, the element lengths of elements 609 and 610 are longer than that of element 607, and the element lengths of elements 611 and 612 are longer than that of element 608. This makes it possible to reduce the SAR of antenna-equipped device 1 without significantly changing the directivity.

[0049] In this modification, L1>L2 and L2≧0 are also satisfied.

[0050] (Variation 2) Next, a configuration in which a dual-band antenna using passive elements is applied to antenna 107 will be described with reference to Fig. 7. Resin part 104 is arranged so as to seal an opening formed in conductor 701, which is a part of conductor 101 that is the top surface of housing 100, and substrate 703, which is a part of substrate 109, is arranged parallel to and facing the opening. Substrate 703 may be a conductor such as another metal plate arranged inside housing 100 or the bottom surface of housing 100.

[0051] The support member 704, which is a dielectric, has two surfaces with different heights, a horizontal surface 704a and a horizontal surface 704c, and further has a vertical surface, a vertical surface 704b, which connects the horizontal surface 704a and the horizontal surface 704c.

[0052] The coaxial cable is composed of a core 705 and an outer sheath 706, and one end of the core 705 is connected to an antenna element 707, and one end of the outer sheath 706 is connected to an antenna element 708 on the vertical plane 704b.

[0053] Element 707 extends along vertical surface 704b and is connected to element 709 on horizontal surface 704a, and element 708 extends along vertical surface 704b in the opposite direction to element 707 and is connected to element 712 on horizontal surface 704c.

[0054] Element 709 extends in horizontal plane 704a and is connected to inductor 710. The other end of inductor 710 is connected to element 711. Element 711 extends in the same direction as element 709, and has the other end that is not connected (open). Element 712 extends in horizontal plane 704c and is connected to inductor 713. The other end of inductor 713 is connected to element 714. Element 714 extends in the same direction as element 712, and has the other end that is not connected (open).

[0055] The inductor 710 and the inductor 713 have the property of exhibiting high impedance in the higher frequency band of the RF signal transmitted and received by the high frequency signal source.

[0056] All of the elements 707 to 714 are made of conductors (thin copper film). The combined length of elements 707, 709, and 711 is approximately equal to the combined length of elements 708, 712, and 714, and is close to ¼ of the wavelength λl on the lower side of the RF signal transmitted and received by the high-frequency signal source.

[0057] The combined length of elements 707 and 709 is approximately equal to the combined length of elements 708 and 712, and is close to 1 / 4 of the wavelength λh on the higher side of the RF signal transmitted and received by the high-frequency signal source.

[0058] By arranging them in this manner, elements 707 and 708 are arranged perpendicular to resin part 104 placed in the opening, and elements 709, 711, 712, and 714 are arranged horizontally. Furthermore, the element lengths of elements 707 and 708 on vertical surface 704b are each ⅛ or less of the wavelength λh on the high-frequency side.

[0059] However, this does not apply when there is no need to reduce the SAR on the high frequency side, such as when SAR is not a problem on the high frequency side or when the high frequency side does not have the maximum radiation direction of the main beam, and it is sufficient if the SAR is 1 / 8 or less of the wavelength λl on the low frequency side.

[0060] In this modified example, the relationship L1>L2 is also established, and L2≧0.

[0061] (Variation 3) Fig. 8 shows a modified example in which a branched monopole antenna is applied for operation in multiple frequency bands. In this example, a two-branched monopole antenna for dual-band operation will be described.

[0062] Conductor 801 indicates a part of conductor 101, which is the top surface of housing 100. Resin part 104 is arranged on conductor 801 so as to seal the opening of the conductor. Substrate 803 is arranged so as to face and parallel to resin part 104. However, substrate 803 may also be another metal plate arranged inside housing 100, or conductor 102 on the bottom surface of housing 100.

[0063] The support member 804, which is a dielectric, has a horizontal surface 804a that is horizontal to the resin part 104, and further has a vertical surface 804b that is perpendicular to 804a and connects to it.

[0064] The coaxial cable is composed of a core 805 and an outer sheath 806, and on vertical plane 804b, one end of core 805 is connected to antenna element 807, and one end of outer sheath 806 is connected to substrate 803. Although not shown in Fig. 8, a balun such as a sleeve balun may be provided near the connection between elements 807 and 808 of the coaxial cable.

[0065] Element 807 extends on vertical surface 804b in a direction perpendicular to resin portion 104, and is connected on horizontal surface 804a to element 808 and element 809 branched from element 808. The element length of element 808 is longer than the element length of element 809.

[0066] Elements 807, 808, and 809 are all conductors (copper thin film). The total length of elements 807 and 808 is close to the wavelength λl / 4 on the lower side of the RF signal transmitted and received by the high-frequency signal source. That is, in this embodiment, the design method for a 1 / 4 wavelength monopole antenna can be used for antenna 107.

[0067] The total length of elements 807 and 809 is close to λh / 4, the wavelength on the higher side of the RF signal transmitted and received by the high-frequency signal source. As a result, elements 808 and 809 are arranged horizontally in a direction that intersects with element 807 relative to resin part 104. In this modification as well, the relationship L1>L2 holds, and L2≧0.

[0068] (Variation 4) Fig. 9 shows a modified example in which a branched dipole antenna is applied for operation in multiple frequency bands. In this example, a two-branched monopole antenna for dual-band operation will be described. Note that in Modification 4, an antenna configuration will be described in which it is not necessary to reduce the SAR on the high-frequency side, but it is necessary to reduce the SAR on the low-frequency side.

[0069] 9, conductor 901 indicates a part of conductor 101 which is the top surface of housing 100, and substrate 903 is shown which is a part of substrate 109 arranged so as to face parallel to conductor 901. Substrate 903 may be a conductor such as another metal plate arranged inside housing 100 or the bottom surface of housing 100.

[0070] The support member 904, which is a dielectric, has two surfaces with different heights, horizontal surface 904a and horizontal surface 904c, and further has a vertical surface, vertical surface 904b, connecting horizontal surface 904a and horizontal surface 904c.

[0071] The coaxial cable is composed of a core 905 and an outer sheath 906, and one end of the core 905 is connected to antenna elements 907 and 910, and one end of the outer sheath 906 is connected to antenna elements 908 and 912, respectively, on the vertical plane 904b.

[0072] Element 907 extends on vertical surface 904b in a direction intersecting the plane on which resin portion 104 is arranged, and is connected to element 909. Element 908 extends on vertical surface 904b in the opposite direction to element 907, and is connected to element 911. Element 910 extends parallel to element 909 along resin portion 104. Element 912 extends parallel to element 911. Elements 910 and 912 have the same axis.

[0073] It should be noted that element 909 is longer than element 910, and element 911 is longer than element 912. Elements 907 to 912 are all made of conductors (thin copper film).

[0074] The combined length of elements 907 and 909 is approximately equal to the combined length of elements 908 and 911, and is close to λl / 4, where λl is the wavelength of the low-frequency radio signal among the RF signals transmitted and received by each high-frequency signal source. Furthermore, the combined length of element 910 and element 912 is approximately equal to λh / 4, and is close to λh / 4, where λh is the wavelength of the high-frequency radio signal among the RF signals transmitted and received by each high-frequency signal source.

[0075] As a result, elements 907 and 908 are arranged in a direction intersecting with resin part 104, and elements 909 to 912 are arranged horizontally with respect to resin part 104.

[0076] Here, the element lengths of elements 907 and 908 are each less than one-eighth (λh / 8) of the wavelength on the high-frequency side. Furthermore, the element length of element 909 is longer than that of element 907, and the element length of element 911 is longer than that of element 908. This makes it possible to reduce the SAR on the low-frequency side of antenna-equipped device 1 without causing a significant change in directivity.

[0077] In this modification, L1>L2 and L2≧0 are also satisfied.

[0078] According to this modification, it is possible to reduce the SAR on the low frequency side while suppressing the reduction in the SAR on the high frequency side. Furthermore, by arranging the antenna on vertical surface 904b, antenna 107 can be configured as a planar antenna.

[0079] <Embodiment 2> 10 shows a plan view of the housing of an antenna-equipped device equipped with an antenna according to this embodiment, and a cross-sectional view taken along line a-a' in the plan view. The antenna-equipped device 10 includes a housing 1000, a support member 1006, an antenna 1007, a power feed unit 1008, and a substrate 1009. The support member 1006, the antenna 1007, the power feed unit 1008, and the substrate 1009 are arranged inside the housing 1000.

[0080] Housing 1000 is composed of conductor 1001 on the top surface, conductor 1002 on the bottom surface parallel to conductor 1001, and conductor 1003 connecting conductors 1001 and 1002 around the entire circumference in the thickness direction. In this embodiment, conductors 1001 to 1003 are all made of steel, and conductors 1001 and 1002 are 300 mm x 300 mm in plan view, and conductor 1003 is 6 mm x 1.5 mm in cross section. Conductor 1001 has an opening of 60 mm x 60 mm, and conductor 1003 has an opening of 60 mm (depth direction in cross section) x 5 mm, and each opening is sealed by resin parts 1004 and 1005, which are dielectrics.

[0081] The support member 1006 is a stepped dielectric member, and is a holding portion that is placed on the conductor 1001 or the resin portion 1004 at a position where the antenna 1007 overlaps with the resin portion 1004 in a plan view.

[0082] Antenna 1007 is a dipole antenna, and is attached to support member 1006 so that feeding portion 1008 is perpendicular to resin portion 1004, and radiates a high-frequency signal as an electromagnetic wave.

[0083] The dipole antenna of antenna 1007 has an element length from feeder 1008 to the open end of each antenna element that is approximately equal and is close to a quarter of the wavelength of the RF signal transmitted from the high-frequency signal source. Specifically, the element length from feeder 1008 to one-eighth of the wavelength of each antenna element is arranged perpendicular to resin part 1004 along support member 1006, and the remaining one-eighth of the wavelength region including the open end of each antenna element is arranged parallel to resin part 1004 along support member 1006. The larger the area of ​​the opening in which dielectric resin parts 1004 and 1005 are arranged, the more the radiation characteristics of electromagnetic waves from antenna 1007 radiated to the outside of antenna-equipped device 10 can be improved. In one example, each of the four sides of resin part 1004 has a length of λ / 2 or more.

[0084] Substrate 1009 is a wireless module on which an electric circuit (not shown) that controls the operation of the housing and mounted components (not shown) are arranged, and serves as a high-frequency signal source that transmits and receives high-frequency signals to be supplied to power supply unit 1008. Substrate 1009 is fixed to conductor 1002, and substrate 1009 and power supply unit 1008 are connected by a coaxial line. Note that substrate 1009 may include a module having a function other than transmitting and receiving high-frequency signals, and may be composed of multiple substrates.

[0085] For example, when the antenna-equipped device 10 is used for digital radiography or the like, the conductor 1002 may be the irradiated surface that receives X-rays, and in this case, the substrate 1009 includes an image processing circuit for X-rays.

[0086] Here, resin part 1004 is located above support member 1006, and when viewed from above in the drawing, the length from the open end of antenna 1007 to the closest side (end) of resin part 1004 at the end of the extension is defined as L1. Similarly, the length from power feed part 1008 to the closest side (end) of resin part 1004 within 1 / 8 of the wavelength λ of each antenna element is defined as L2.

[0087] In this embodiment, it is assumed that L1>L2 and L2≧0.

[0088] As in the first embodiment, when observed in the near field of the antenna 1007, that is, at a location outside the housing 1000 close to the resin part 1004, the electric field component parallel to the resin part 1004, that is, the horizontal direction, contributes more to the SAR than the electric field component in the vertical direction. Therefore, by arranging up to 1 / 8 of the wavelength λ of the antenna element connected to the power feed part 1008 in a direction intersecting the resin part 1004, it is possible to attenuate the electric field component parallel to the resin part 1004 and reduce the SAR. On the other hand, when observed in the far field of the antenna 1007, the main beam radiated by the antenna 1007 maintains a direction that penetrates the resin part 1004.

[0089] <Other embodiments> Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist of the present invention.

[0090] 1 shows that one opening is formed in the conductor 101. However, multiple openings may be provided, and for example, if the antenna-equipped device 1 has multiple antennas 107, an opening may be provided for each antenna 107.

[0091] Moreover, the antennas of the first to fourth modifications may be applied to the antenna 1007 of the second embodiment.

[0092] [Summary of the embodiment] At least some of the above-described embodiments can be summarized as follows.

[0093] (Item 1) An antenna device disposed inside a conductive housing, the housing has a first surface and a second surface opposite to the first surface, the conductor on the first surface has at least one opening; The antenna device includes: a first element including a first feed end and extending in a direction transverse to the first plane; a second element extending along the first surface, the second element having a first open end and a connection with the first element; Including, the first and second elements are disposed at positions overlapping the opening in a direction perpendicular to the first surface; An antenna device characterized in that, when viewed in a direction perpendicular to the first surface, the shortest distance from the first open end of the second element to the edge of the aperture is longer than the shortest distance from the first feeding end of the first element to the edge of the aperture.

[0094] (Item 2) The antenna device described in item 1, characterized in that the housing is an approximately rectangular parallelepiped and the distance between the first surface and the second surface is less than 1 / 4 of the wavelength of the electromagnetic waves transmitted and received by the antenna device.

[0095] (Item 3) The antenna device according to item 1 or 2, characterized in that the opening is rectangular, and the length of each side of the opening is equal to or less than half the wavelength of the electromagnetic waves transmitted and received by the antenna device.

[0096] (Item 4) The antenna device described in any one of items 1 to 3, characterized in that the length of the first element is shorter than the length of the second element and is 1 / 8 or less of the wavelength of the electromagnetic waves transmitted and received by the antenna device.

[0097] (Item 5) 5. The antenna device according to any one of items 1 to 4, wherein the second element radiates an electromagnetic wave having an electric field component parallel to the first plane.

[0098] (Item 6) 6. The antenna device according to any one of items 1 to 5, wherein the opening is covered with a dielectric.

[0099] (Item 7) 7. The antenna device according to any one of items 1 to 6, wherein a holding portion for holding the antenna device is disposed on the second surface of the housing.

[0100] (Item 8) 7. The antenna device according to any one of items 1 to 6, wherein a holder for holding the antenna device is disposed on the first surface of the housing.

[0101] (Item 9) The antenna device includes: a third element including a second feed end and extending in a direction transverse to the first plane; a fourth element extending along the first surface, the fourth element including a second open end and a connection with the third element; 9. The antenna device according to any one of items 1 to 8, which is a dipole antenna further comprising:

[0102] (Item 10) 10. The antenna device according to item 9, wherein the extending direction of the first element from the first feeding end is different from the extending direction of the third element from the second feeding end.

[0103] (Item 11) A conductive housing, a first surface and a second surface opposite the first surface; The conductor on the first surface has at least one opening therein. The housing and An antenna device disposed inside the housing, a first element including a first feed end and extending in a direction transverse to the first plane; a first element extending along the first surface, the first element including a first open end and a connection portion with the first element; Including, the first and second elements are disposed at positions overlapping the opening in a direction perpendicular to the first surface; an antenna device in which, as viewed in a direction perpendicular to the first surface, a shortest distance from the first open end of the second element to an edge of the aperture is longer than a shortest distance from the first feed end of the first element to the edge of the aperture; An antenna-equipped device comprising:

[0104] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0105] 1, 10: Antenna-embedded device, 100, 1000: Housing, 101, 102, 103, 201, 203, 401, 403, 601, 603, 701, 703, 801, 803, 901, 1001, 1002, 1003: Conductor, 104, 105, 1004, 1005: Resin part, 106, 204, 404, 604, 704, 804, 904, 1006: Support member, 107, 1007: Antenna, 207-210, 407, 408, 607-612, 707-711, 807-809, 907-912: Element, 108, 1008: Power supply section, 204a, 204c, 404a, 604a, 604c, 704a, 704c, 804a, 904a, 904c: horizontal surface, 204b, 604b, 704bc, 804b, 904b: vertical surface, 205, 405, 605, 705, 805, 905: core wire, 206, 406, 606, 706, 806, 906: outer cover, 710, 712: inductor

Claims

1. An antenna device disposed inside a conductive housing, the housing has a first surface and a second surface opposite to the first surface, the conductor on the first surface has at least one opening; The antenna device includes: a first element including a first feed end and extending in a direction transverse to the first plane; a second element connected to the first element and extending along the first surface, the second element including a first open end; Including, the first and second elements are disposed at positions overlapping the opening in a direction perpendicular to the first surface; An antenna device characterized in that, when viewed in a direction perpendicular to the first surface, the shortest distance from the first open end of the second element to the edge of the aperture is longer than the shortest distance from the first feed end of the first element to the edge of the aperture.

2. 2. The antenna device according to claim 1, wherein the housing is an approximately rectangular parallelepiped, and the distance between the first surface and the second surface is less than 1 / 4 of the wavelength of the electromagnetic waves transmitted and received by the antenna device.

3. 2. The antenna device according to claim 1, wherein the opening is rectangular, and the length of each side of the opening is equal to or less than half the wavelength of the electromagnetic waves transmitted and received by the antenna device.

4. 2. The antenna device according to claim 1, wherein the length of the first element is shorter than the length of the second element and is equal to or less than 1 / 8 of the wavelength of the electromagnetic waves transmitted and received by the antenna device.

5. 2. The antenna device according to claim 1, wherein the second element radiates an electromagnetic wave having an electric field component parallel to the first plane.

6. 2. The antenna device according to claim 1, wherein the opening is covered with a dielectric material.

7. The antenna device according to claim 1 , wherein a holding portion for holding the antenna device is disposed on the second surface of the housing.

8. The antenna device according to claim 1 , wherein a holder for holding the antenna device is disposed on the first surface of the housing.

9. The antenna device includes: a third element including a second feed end and extending in a direction transverse to the first plane; a fourth element including a second open end, connected to the third element, and extending along the first surface; 2. The antenna device according to claim 1, wherein the antenna device is a dipole antenna further comprising:

10. 10. The antenna device according to claim 9, wherein the extending direction of the first element from the first feeding end is different from the extending direction of the third element from the second feeding end.

11. A conductive housing, a first surface and a second surface opposite the first surface; The conductor on the first surface has at least one opening therein. The housing and An antenna device disposed inside the housing, a first element including a first feed end and extending in a direction transverse to the first plane; a first element including a first open end, connected to the first element and extending along the first surface; Including, the first and second elements are disposed at positions overlapping the opening in a direction perpendicular to the first surface; an antenna device in which, as viewed in a direction perpendicular to the first surface, a shortest distance from the first open end of the second element to an edge of the aperture is longer than a shortest distance from the first feed end of the first element to the edge of the aperture; An antenna-equipped device comprising:

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