Helical antenna, antenna apparatus, and communication device

Abstract

[Problem] To provide a helical antenna in which the rust-preventive properties, dust resistance, and damage resistance of an antenna element are improved, and which has high durability. [Solution] Provided is a helical antenna 1 in which a columnar dielectric core 2, antenna elements 3, 4 having a helical pattern, and a resin tube 5 are disposed in this order from the inside toward the outside, wherein the resin tube 5 is joined to an outer peripheral surface of the dielectric core 2 in the vicinity of where the antenna elements 3, 4 are covered. The resin tube 5 is longer than the dielectric core 2. The antenna elements 3, 4 include a first antenna element 3 which is relatively shorter in correspondence with the length of the dielectric core 2 and a second antenna element 4 which is relatively longer in correspondence with the length of the resin tube 5. The inside of a portion of the second antenna element 4 that extends past dielectric core 2 is an air region.

Description

Helical antenna, antenna device and communication equipment

[0001] The present invention relates to a helical antenna, an antenna device, and a communication device.

[0002] Helical antennas used in mobile communication devices, in-vehicle communication devices, etc. are generally made by forming a spiral antenna element on a cylindrical dielectric core. These helical antennas are required to be compact and have a high working gain.

[0003] Patent Document 1 discloses a helical antenna that is compatible with two GPS frequencies (1227.6 MHz and 1575.42 MHz) by forming a long spiral first antenna element and a short spiral second antenna element on the outer peripheral surface of a cylindrical core made of ceramic material by metallizing with plating or other methods. Although this helical antenna is compact, it is necessary to make the core long enough to form the long first antenna element.

[0004] Patent Document 2 discloses a helical antenna that supports the two frequencies, in which a short internal antenna element is formed by metallizing the outer peripheral surface of a short internal core made of a ceramic material, and a long external antenna element is formed by metallizing the outer peripheral surface of a long external core made of a cylindrical resin material, and the internal core is housed inside the external core. This helical antenna has a simple structure that can be made even smaller.

[0005] Special Publication No. 2012-520594 Publication Patent No. 6568332

[0006] Helical antennas used in applications such as the above-mentioned portable communication devices require not only miniaturization and working gain performance, but also rust resistance, dust resistance, and scratch resistance of the antenna element. However, up until now, little research has been done on the rust resistance, dust resistance, and scratch resistance of antenna elements.

[0007] In Patent Document 1, the first and second antenna elements, which are metallized on the outer circumferential surface of the core, are exposed to the outside. In Patent Document 2, the external antenna element, which is metallized on the outer circumferential surface of the outer core, is exposed to the outside, and the inner core is simply inserted into the resin outer core without being bonded (floating), so the internal antenna element, which is metallized on the outer circumferential surface of the inner core, is also exposed to air inside the outer core. This raises the risk of the antenna element rusting, becoming covered with dust, or being damaged.

[0008] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a helical antenna having improved rust resistance, dust resistance and scratch resistance of the antenna element and high durability.

[0009] In the present invention, when we simply refer to "long" or "short," we mean the length in the direction of the axis passing through the center of the dielectric core. Furthermore, "inner" means the side approaching the axis, and "outer" means the side away from the axis.

[0010] [1] A helical antenna in which a cylindrical dielectric core, a spiral-patterned antenna element, and a resin tube are arranged from the inside to the outside, and the resin tube is joined to the outer surface of the dielectric core near where it covers the antenna element. (Function) The resin tube seals and protects the antenna element from exposure to air, dust, collision objects, etc.

[0011] [2] A helical antenna including a cylindrical dielectric core, a spiral-patterned antenna element bonded to the outer surface of the dielectric core, and a resin tube bonded to the outer surface of the antenna element and to the outer surface of the dielectric core. (Function) The resin tube bonded to the outer surface of the antenna element and bonded by adhesive to the outer surface of the dielectric core protects the antenna element from exposure to air, dust, colliding objects, etc.

[0012] [3] The helical antenna according to [1] or [2], wherein the antenna element is bonded to the outer peripheral surface of the dielectric core with an adhesive. (Function) Protection of the antenna element is improved.

[0013] [4] The helical antenna according to [1] or [2], wherein the resin tube has a thickness of 10 to 100 μm. (Function) The antenna has a good balance between strength and flexibility, and provides improved protection for the antenna element.

[0014] [5] The helical antenna according to any one of [1] to [4], wherein the resin tube is formed by winding a resin film. (Function) The resin tube can be easily formed.

[0015] [6] A helical antenna according to [5], in which an assembly of a resin film, an antenna element bonded to the inner surface of the resin film, and a double-sided adhesive tape covering the antenna element and attached to the inner surface of the resin film is wound around the outer surface of a dielectric core to form a resin tube, and the resin tube is bonded to the outer surface of the dielectric core with the adhesive of the double-sided adhesive tape. (Function) The helical antenna can be easily manufactured.

[0016] [7] A helical antenna according to any one of [1] to [6], in which the resin tube is longer than the dielectric core, the antenna element includes a first antenna element that is relatively short corresponding to the length of the dielectric core, and a second antenna element that is relatively long corresponding to the length of the resin tube, and the inside of the portion of the second antenna element that protrudes beyond the dielectric core is an air region. (Function) Because the antenna element includes a relatively short first antenna element and a relatively long second antenna element, it can accommodate multiple frequencies. Furthermore, the presence of an air region in the second antenna element allows for weight reduction, or allows frequency adjustment by providing a separate dielectric core.

[0017] [8] A helical antenna according to any one of [1] to [7], wherein the resin tube is made of a resin having a flexural modulus (JIS K7171:2022, test condition 2 mm / min) of 2500 MPa or more and a glass transition temperature Tg (JIS K7121:2012) of 220°C or more. (Function) The rigidity of the resin tube is improved (in [7], it becomes easier to form an air region), and heat resistance during soldering of the antenna element is improved.

[0018] [9] The helical antenna according to any one of [1] to [8], wherein the antenna system is an end-fire type. (Operation) There is no need to provide a transmission line that penetrates the dielectric core.

[0019]

[10] The helical antenna according to any one of [1] to [9], wherein the antenna element is a closed circuit. (Function) The working gain performance is improved.

[0020]

[11] An antenna device including the helical antenna according to any one of [1] to

[10] , a connection board having a feeding point to the helical antenna, and a circuit board having an amplifier connected to the connection board.

[0021]

[12] A communication device incorporating the helical antenna according to any one of [1] to

[10] above.

[0022] According to the present invention, it is possible to improve the rust resistance, dust resistance, and scratch resistance of the antenna element, and to provide a highly durable helical antenna.

[0023] FIG. 1 is an exploded perspective view of a helical antenna and an antenna device according to an embodiment. FIG. 2 shows an assembly of a resin film, an antenna element, and double-sided adhesive tape, where (a) is a front view of the assembly, (b) is an A-A cross-sectional view of the resin film with the antenna element attached, and (c) is an A-A cross-sectional view of the resin film with the double-sided adhesive tape further attached. FIG. 3 shows the manufacturing process of a helical antenna, where (a) is a perspective view of the assembly wound around a dielectric core and the upper end of a first antenna element soldered, (b) is a partial perspective view of the second antenna element soldered, and (c) is a partial perspective view of the lower end of each antenna element soldered. FIG. 4 is a perspective view of an antenna device. FIG. 5(a) is a partial vertical cross-sectional view of the dielectric core before the assembly is wound, and (b) is a partial vertical cross-sectional view of the helical antenna after the assembly is wound. FIG. 6 shows a helical antenna according to a modified embodiment, where (a) is a partial vertical cross-sectional view of the dielectric core before the assembly is wound, and (b) is a partial vertical cross-sectional view of the helical antenna after the assembly is wound.

[0024] <1> Dielectric Core The dielectric that forms the dielectric core is not particularly limited as long as it is a solid dielectric that can be formed into a columnar shape, and examples thereof include ceramic, resin, rubber, glass, quartz, etc. The columnar shape is not particularly limited, and examples thereof include a circular columnar shape, an elliptical columnar shape, an oblong columnar shape, a rectangular columnar shape, etc. The columnar shape is not limited to one without holes, and includes one with holes such as a cylindrical shape.

[0025] <2> Resin Tube The resin used to form the resin tube is not particularly limited, but examples include polyimide, polyethersulfone (PES), polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP), and acrylonitrile-butadiene-styrene copolymer (ABS). In terms of rigidity and heat resistance, polyimide, PES, PET, and PC are preferred. As mentioned above, resins with a flexural modulus of 2500 MPa or higher and a glass transition temperature (Tg) of 220°C or higher are more preferred, and resins with a flexural modulus of 3000 MPa or higher and a glass transition temperature (Tg) of 300°C or higher are most preferred. The thickness of the resin tube is not particularly limited, but is preferably 10 to 100 μm, more preferably 12 to 50 μm. The means for forming the resin tube is not particularly limited, but examples include a resin tube formed by wrapping a resin film around it.

[0026] <3> Antenna Element The material for forming the spiral pattern antenna element is not particularly limited, but examples include metals such as copper, aluminum, and silver (including alloys of each). The antenna element in the above-mentioned means [1] or [2] includes the following aspects: (a) an aspect in which there is one antenna element with a predetermined spiral pattern; (b) an aspect in which there are multiple antenna elements with the same spiral pattern; (c) an aspect in which there is one antenna element with different spiral patterns; (d) an aspect in which there are multiple antenna elements with different spiral patterns; (e) an aspect in which one antenna element with different spiral patterns is combined with multiple others. The antenna element in the above-mentioned means [7] includes the following aspects: (f) an aspect in which there is one first antenna element and one second antenna element; (g) an aspect in which there are multiple first antenna elements and multiple second antenna elements; (h) an aspect in which there is one first antenna element and one second antenna element combined with multiple others.

[0027] The means for forming the antenna element is not particularly limited, but the following embodiments can be exemplified: (K) An antenna element obtained by plating, sputtering, metallizing, printing, etc., a resin film for a resin tube with a metal; (L) An antenna element obtained by bonding a metal foil to a resin film for a resin tube with an adhesive; (M) An antenna element obtained by plating, sputtering, metallizing, printing, etc., a dielectric core with a metal;

[0028] <4> Bonding The means for joining the resin tube and the dielectric core are not particularly limited, but examples include bonding with an adhesive, fusion bonding, thermal compression, bonding with a spacer such as a sponge or a wedge, caulking, screw fastening, etc. Bonding with an adhesive is preferred because of its good adhesion and sealing properties, and is also preferred because it allows for easy bonding, especially when the resin tube is made of polyimide. The adhesive is not particularly limited, but double-sided adhesive tape is preferred because of its good bonding workability. The means for joining the antenna element and the dielectric core are not particularly limited, but examples include bonding by plating, sputtering, metallization, printing, etc. in the above embodiment (S), and bonding by adhesive is preferred in the above embodiments (K) and (L). The adhesive is not particularly limited, but double-sided adhesive tape is preferred because of its good bonding workability. The means for joining the antenna element and the resin tube are not particularly limited, but examples include bonding by plating, sputtering, metallization, printing, etc. in the above embodiments (K) and (L), and bonding by adhesive is preferred in the above embodiment (S). The adhesive is not particularly limited, but a double-sided adhesive tape is preferred because of its good adhesive workability.

[0029] <5> Applications The helical antenna of the present invention is not particularly limited in its applications, but can be suitably used in various communication devices (including information devices) that receive, transmit, or both radio waves. The communication devices may be fixed communication devices, but mobile communication devices are suitable because they can take advantage of the compact size of the present invention. Examples of mobile communication devices include portable communication devices (transceivers, personal digital assistants, mobile phones, etc.), in-vehicle communication devices (car navigation systems, in-vehicle information terminals, in-vehicle phones, etc.), and drone-mounted communication devices. The content of communication is not particularly limited, but examples include GPS data, general data, and phone calls.

[0030] Next, specific examples of the present invention will be described with reference to the drawings. Note that the materials, quantities, and conditions of each part in the examples are examples and can be changed as appropriate without departing from the gist of the invention.

[0031] The antenna device of the embodiment shown in Figures 1 to 5 includes a helical antenna 1, a circuit board 12 having an amplifier connected to a connection board 10 of the helical antenna 1, a shielding case 13 for the circuit board 12, and a connector 14 for connecting a coaxial cable.

[0032] The key feature of the helical antenna 1 is that, as shown in Figure 5 etc., a cylindrical dielectric core 2, spiral-patterned antenna elements 3 and 4, and a resin tube 5 are arranged in this order from the inside to the outside, and the resin tube 5 is bonded with an adhesive to the outer surface of the dielectric core 2 in the vicinity where it covers the antenna elements.

[0033] In other words, the helical antenna 1 includes a cylindrical dielectric core 2, spiral-patterned antenna elements 3 and 4 joined to the outer surface of the dielectric core 2, and a resin tube 5 joined to the outer surfaces of the antenna elements 3 and 4 and also joined to the outer surface of the dielectric core 2 with an adhesive.

[0034] The helical antenna 1 will be described in detail below. The dielectric core 2 is made of a ceramic material (main component: MgO—TiO 2 ) and is formed into a cylindrical shape with a length of 18 mm and an outer diameter of 14 mm. Although there is a through hole at the axial center of the dielectric core 2 in the illustrated example, this through hole is not necessary. This is because, as will be described later, the helical antenna 1 of this embodiment is an end-fire type. However, if it is changed to a back-fire type, a through hole is necessary to pass the transmission line through.

[0035] The resin tube 5 is formed by winding a 20 μm thick resin film 6 made of polyimide into a cylindrical shape with a length of 23 mm and an inner diameter of 15 to 16 mm. In other words, the resin tube 5 is longer than the dielectric core 2. The dielectric core 2 and the resin tube 5 are aligned at the same bottom level, and the resin tube 5 protrudes above the dielectric core 2. The polyimide used has a flexural modulus (JIS K7171:2022, test condition 2 mm / min) of 3500 MPa and a glass transition temperature Tg (JIS K7121:2012) of 335°C.

[0036] The antenna elements 3, 4 include a first antenna element 3 that is relatively short corresponding to the length of the dielectric core 2 and a second antenna element 4 that is relatively long corresponding to the length of the resin tube 5, and the inside of the portion of the second antenna element 4 that protrudes beyond the dielectric core 2 is an air region (air core). The first antenna element 3 and the second antenna element 4 are each made of copper foil with a line width of 1 mm and a thickness of 35 μm, and there are four of each, arranged alternately at intervals in the circumferential direction.

[0037] The resin tube 5 and the antenna elements 3 and 4 are bonded to the outer peripheral surface of the dielectric core 2 with double-sided adhesive tape 7. As shown in FIG. 2, the resin film 6 forming the resin tube 5, the antenna elements 3 and 4, and the double-sided adhesive tape 7 are pre-assembled. As shown in FIG. 2(a), the resin film 6 forms a parallelogram in front view. As shown in FIG. 2(b), the first antenna element 3 and the second antenna element 4 are bonded to the inner surface of the resin film 6 with an adhesive (solvent-soluble polyimide varnish (PIAD)). As shown in FIG. 2(c), the double-sided adhesive tape 7 is further adhered to complete the assembly. For example, Nitto Denko Corporation's No. 5605R (a 50 μm-thick tape with an acrylic adhesive attached to both sides of a polyester film) is used as the double-sided adhesive tape 7. The resin film 6 is flat in FIG. 2(b), but tends to deform to surround the antenna elements 3 and 4 due to tension from the double-sided adhesive tape 7 in FIG. 2(c).

[0038] The hatched areas in FIG. 2A, that is, the ends of the antenna elements 3 and 4, are not covered with double-sided adhesive tape so as to be exposed for soldering, which will be described later.

[0039] Then, as shown in Figures 1, 3, 5, etc., this assembly is wound around the outer peripheral surface of the dielectric core 2 to form a resin tube 5, and the resin tube 5 is bonded to the outer peripheral surface of the dielectric core 2 in the vicinity of where it covers the antenna element with the adhesive (adhesive) of the double-sided adhesive tape 7, and the antenna elements 3 and 4 are also bonded to the outer peripheral surface of the dielectric core 2 with the same adhesive.

[0040] The upper ends of the four first antenna elements 3 are soldered to a first connecting conductor 8 in a cross pattern formed by metallization on the upper end surface of the dielectric core 2 (shown by circles in FIG. 3( a)), forming a closed circuit. The upper ends of the four second antenna elements 4 are soldered to a second connecting conductor 9 made of a cross-shaped metal plate placed on the upper end of the resin tube 5 (shown by circles in FIG. 3( b)), forming a closed circuit. The lower ends of each antenna element 3, 4 are soldered to a feeding point 11 of a connecting board 10 that is attached to the upper end of the resin tube 5 (shown by circles in FIG. 3( c)). In other words, the helical antenna 1 of this embodiment is an end-fire type antenna.

[0041] The helical antenna 1 of this embodiment configured as described above has the following advantages. (1) The resin tube 5 protects the antenna elements 3 and 4 from exposure to air, dust, colliding objects, etc., resulting in a highly durable helical antenna 1 with improved rust resistance, dust resistance, and scratch resistance. (2) The antenna elements 3 and 4 are bonded to the outer circumferential surface of the dielectric core 2 with an adhesive, thereby improving protection of the antenna elements 3 and 4. (3) The resin tube 5 is formed by wrapping the resin film 6, so the resin tube 5 can be easily formed. (4) The helical antenna 1 is easily manufactured because the assembly is wound around the outer circumferential surface of the dielectric core 2. (5) The relatively short first antenna element 3 and the relatively long second antenna element 4 allow the antenna elements 1 to support multiple frequencies (e.g., 1575.42 MHz, 1227.6 MHz). (6) The inside of the portion of the second antenna element 4 that protrudes beyond the dielectric core 2 is an air region (air core), which allows for weight reduction, or it is possible to provide another dielectric core 2 for frequency adjustment. (7) The resin tube 5 is made of polyimide, which improves rigidity and makes it easy to form an air region. It also improves heat resistance during soldering of the antenna elements 3 and 4. (8) The antenna system is an end-fire type, which eliminates the need for a transmission line that penetrates the dielectric core 2. (9) The antenna elements 3 and 4 are closed circuits, which improves the operating gain performance. (10) Even compared to Patent Document 2, it is possible to achieve even smaller and lighter size. (11) The number of parts is reduced, which allows for cost reduction.

[0042] 1 and 4, the helical antenna 1 of this embodiment can be configured as an antenna device by connecting a circuit board 12 having an amplifier to a connection board 10, and further providing a shielding case 13 for the circuit board 12 and a connector 14 for connecting a coaxial cable, as necessary. This helical antenna 1 or antenna device is small and lightweight, and can be incorporated into the various communication devices mentioned above.

[0043] The present invention is not limited to the above-described embodiment, and can be appropriately modified and embodied without departing from the spirit of the invention. (1) As shown in the modified example in Figure 6, the first antenna element 3 may be formed directly on the outer circumferential surface of the dielectric core 2 by plating, sputtering, metallization, printing, etc., and only the second antenna element 4 may be provided on the resin tube 5 as in the above-described embodiment. However, the above-described embodiment has better manufacturing efficiency. (2) The antenna system may be changed to an end-fire type. (3) The antenna elements 3 and 4 may be changed to an open circuit.

[0044] REFERENCE SIGNS LIST 1 helical antenna 2 dielectric core 3 first antenna element 4 second antenna element 5 resin tube 6 resin film 7 double-sided adhesive tape 8 first connecting conductor 9 second connecting conductor 10 connecting board 11 feeding point 12 circuit board 13 shielding case 14 connector

Claims

1. A helical antenna in which a columnar dielectric core, a helical-pattern antenna element, and a resin tube are arranged in order from the inside to the outside, and the resin tube is joined to the outer peripheral surface of the dielectric core in the vicinity of covering the antenna element.

2. A helical antenna including a columnar dielectric core, an antenna element of a helical pattern joined to the outer peripheral surface of the dielectric core, and a resin tube joined to the outer surface of the antenna element and joined to the outer peripheral surface of the dielectric core.

3. The helical antenna according to claim 1 or 2, wherein the antenna element is joined to the outer peripheral surface of the dielectric core with an adhesive.

4. The helical antenna according to claim 1 or 2, wherein the resin tube has a thickness of 10 to 100 μm.

5. The helical antenna according to claim 1 or 2, wherein the resin tube is formed by winding a resin film.

6. An assembly of a resin film, an antenna element joined to the inner surface of the resin film, and a double-sided adhesive tape adhered to the inner surface of the resin film covering the antenna element is wound around the outer peripheral surface of the dielectric core to form a resin tube, and the resin tube is joined to the outer peripheral surface of the dielectric core with the adhesive of the double-sided adhesive tape. The helical antenna according to claim 5.

7. The resin tube is longer than the dielectric core, and the antenna element includes a first antenna element that is relatively short corresponding to the length of the dielectric core and a second antenna element that is relatively long corresponding to the length of the resin tube. The helical antenna according to claim 1 or 2, wherein the inside of the portion of the second antenna element that protrudes beyond the dielectric core is an air region.

8. The helical antenna according to claim 7, wherein the resin tube is made of a resin having a flexural modulus (JIS K7171: 2022, test condition 2 mm / min) of 2500 MPa or more and a glass transition temperature Tg (JIS K7121: 2012) of 220 °C or more.

9. The helical antenna according to claim 1 or 2, wherein the antenna type is an end-fire type.

10. The helical antenna according to claim 1 or 2, wherein the antenna element is a closed circuit.

11. An antenna device including the helical antenna according to claim 1 or 2, a connection substrate having a power supply point to the helical antenna, and a circuit substrate connected to the connection substrate and having an amplifier.

12. A communication device incorporating the helical antenna according to claim 1 or 2.

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