Helical antenna, antenna apparatus, and communication device

Abstract

To provide a highly durable helical antenna with improved rust-proof properties, dust-proof properties, and scuff-proof properties of antenna elements. A helical antenna 1, in which a dielectric core 2 that is columnar in shape, antenna elements 3 and 4 that have helical patterns, and a resin tube 5, are disposed in that order from inside to outside, and the resin tube 5 is joined to an outer peripheral face of the dielectric core 2 in a vicinity at which the antenna elements 3 and 4 are covered. The resin tube 5 is longer than the dielectric core 2, the antenna elements 3 and 4 include first antenna elements 3 which are relatively short in accordance with a length of the dielectric core 2, and second antenna elements 4 which are relatively long in accordance with a length of the resin tube 5, and inside of a portion of the second antenna elements 4 that protrudes beyond the dielectric core 2 is an air region.

Description

TECHNICAL FIELD

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

[0002] Helical antennas used in applications such as portable communication equipment, in-vehicle communication equipment, and so forth, are commonly fabricated by forming a helical antenna element on a dielectric core that is columnar in shape. This helical antenna is required to be compact and to have high operational gain performance.

[0003] Patent Document 1 discloses that a first antenna element, which is long and has a helical shape, and a second antenna element, which is short and has a helical shape, are metallized by plating or some other method on an outer peripheral face of a core that is formed of a ceramic material in a columnar shape, thereby forming a helical antenna that is compatible with two GPS frequencies (1227.6 MHz and 1575.42 MHz). Although this helical antenna is reduced in size, there is a need for the core to be sufficiently long to form the first antenna element that is long.

[0004] Also, Patent Document 2 discloses an invention of a helical antenna that is compatible with the above two frequencies, in which an inner antenna element, which is short and has a helical shape, is formed by metallization processing on an outer peripheral face of an inner core, which is short and made of a ceramic material, and in which an outer antenna element, which is long and has a helical shape, is formed by metallization processing on an outer peripheral face of an outer core, which is long and formed of a resin material in a cylindrical shape, and the inner core is accommodated inside the outer core. This helical antenna has a simple structure that can be further reduced in size.PRIOR ART DOCUMENTSPatent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication (Translation of PCT Application) No. 2012-520594 (JP 2012-520594 A) Patent Document 2: Japanese Patent No. 6568332 SUMMARY OF THE INVENTIONProblem to be Solved by the Invention

[0006] Helical antennas used in applications such as the above mobile communication equipment and so forth require not only reduction in size and operational gain performance, but also rust-proof properties, dust-proof properties, and scuff-proof properties of the antenna elements. However, so far, little consideration has been given to the rust-proof properties, dust-proof properties, and scuff-proof properties of antenna elements.

[0007] In Patent Document 1, first and second antenna elements that are metalized on the outer peripheral face of the core are externally exposed. In Patent Document 2, the outer antenna element, which is formed by metallization processing on the outer peripheral face of the outer core, is externally exposed, while the inner core is only inserted into the outer core made of resin and not bonded (is floating), and accordingly, the inner antenna element, which is formed by metallization processing on the outer peripheral face of the inner core, is also exposed to air inside the outer core. Accordingly, there was concern that the antenna elements would rust, be covered with dust, or be scuffed.

[0008] Accordingly, an object of the present invention is to provide a highly durable helical antenna with improved rust-proof properties, dust-proof properties, and scuff-proof properties of the antenna elements.Means for Solving the Problems

[0009] In the present invention, when the terms "long" and "short" are simply used as such, these refer to a length in a direction of an axis passing through the center of the dielectric core. Additionally, "inside" refers to a side approaching the axis, and "outside" refers to a side away from the axis. [1] A helical antenna, in which a dielectric core that is columnar in shape, an antenna element that has a helical pattern, and a resin tube, are disposed in that order from the inside to the outside, and the resin tube is joined to an outer peripheral face of the dielectric core in a vicinity at which the antenna element is covered. (Function) The resin tube seals and protects the antenna element from exposure to air, dust, colliding objects, and so forth. [2] A helical antenna, including a dielectric core that is columnar in shape, an antenna element that has a helical pattern and that is joined to an outer peripheral face of the dielectric core, and a resin tube that is joined to an outer side face of the antenna element and that is also joined to the outer peripheral face of the dielectric core. (Function) The resin tube joined to the outer side face of the antenna element and also joined to the outer peripheral face of the dielectric core by bonding protects the antenna element from being exposed to air, dust, colliding objects, and so forth. [3] The helical antenna according to [1] or [2], wherein the antenna element is joined to the outer peripheral face of the dielectric core by an adhesive. (Function) Protection of the antenna element is improved. [4] The helical antenna according to [1] or [2], wherein the resin tube has a thickness of 10 to 100 µm. (Function) Balance between strength and flexibility is good, and protection of the antenna element is improved. [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. [6] The helical antenna according to [5], wherein the resin tube is formed by an assembly of the resin film, the antenna element joined to an inner face of the resin film, and double-sided adhesive tape that covers the antenna element and that is bonded to the inner face of the resin film is wound around the outer peripheral face of the dielectric core, and also the resin tube is joined to the outer peripheral face of the dielectric core by an adhesive of the double-sided adhesive tape. (Function) The helical antenna can be easily manufactured. [7] The helical antenna according to any one of [1] to [6], wherein the resin tube is longer than the dielectric core, the antenna element includes a first antenna element that is relatively short in accordance with a length of the dielectric core, and a second antenna element that is relatively long in accordance with a length of the resin tube, and inside of a portion of the second antenna element that protrudes beyond the dielectric core is an air region. (Function) The antenna element includes a first antenna element that is relatively short and a second antenna element that is relatively long, and accordingly is compatible with a plurality of frequencies. Also, having the air region in the second antenna element, and accordingly the weight thereof can be reduced, or alternatively, another dielectric core can be provided to adjust the frequency. [8] The helical antenna according to any one of [1] to [7], wherein the resin tube is made of a resin having a bending elastic modulus (JIS K 7171:2022, test conditions 2 mm / min) of 2500 Mpa or more and a glass transition temperature Tg (JIS K 7121:2012) of 220°C or higher. (Function) Rigidity of the resin tube is improved (formation of the air region in [7] is facilitated), and also heat resistance during soldering or the like of the antenna elements is improved. [9] The helical antenna according to any one of [1] to [8], wherein an antenna system is an end-fire type. (Function) There is no need to provide a transmission line that passes through the dielectric core.

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

[11] An antenna device, including the helical antenna according to any one of the above [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.

[12] Communication equipment in which is incorporated the helical antenna according to any one of the above [1] to

[10] . Effects of the Invention

[0010] According to the present invention, a highly durable helical antenna can be provided with improved rust-proof properties, dust-proof properties, and scuff-proof properties of antenna elements.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is an exploded perspective view of a helical antenna and an antenna device according to an embodiment; FIGS. 2A to 2C illustrate an assembly of a resin film, an antenna element, and double-sided adhesive tape, in which 2A is a front view of the assembly, 2B is a cross-sectional view taken along A-A when the antenna element is provided on the resin film, and 2C is a cross-sectional view taken along A-A when the double-sided adhesive tape is further provided; FIGS. 3A to 3C illustrate a manufacturing process of the helical antenna, in which 3A is a perspective view of the assembly wound around a dielectric core with an upper end portion of a first antenna element soldered, 3B is a partial perspective view of an upper end portion of a second antenna element soldered, and 3C is a partial perspective view of lower ends of the antenna elements soldered; FIG. 4 is a perspective view of the antenna device; FIG. 5A is a partial longitudinal-sectional view of the dielectric core and so forth before the assembly is wound, and 5B is a partial longitudinal-sectional view of the helical antenna after the assembly is wound; and FIGS. 6A and 6B illustrate a helical antenna according to a modification of the embodiment, in which 6A is a partial longitudinal-sectional view of a dielectric core and so forth before winding an assembly, and 6B is a partial longitudinal - sectional view of the helical antenna after winding the assembly. MODES FOR CARRYING OUT THE INVENTION<1> Dielectric Core

[0012] Dielectric material of which a dielectric core is made is not limited in particular, as long as it is a solid dielectric material that can be formed into a columnar shape, examples of which include ceramic, resin, rubber, glass, quartz, and so forth.

[0013] Examples of the columnar shape include a columnar shape, an elliptical columnar shape, an oval columnar shape, a prismatic columnar shape, and so forth, although not limited thereto in particular. The columnar shape is not limited to one without a hole, but also includes one with a hole such as a cylindrical shape or the like.<2> Resin Tube

[0014] Examples of resin that a resin tube is made of include polyimide, polyethersulfone (PES), polyethylene terephthalate (PET), polycarbonate (PC), polypropylene (PP), an acrylonitrile butadiene styrene copolymer (ABS), and so forth, although not limited thereto in particular. In terms of rigidity and heat resistance, polyimide, PES, PET, PC, and so forth are preferable, and as described above, resins that satisfy a bending elastic modulus of 2500 Mpa or more and a glass transition temperature Tg of 220°C or higher are more preferable, and most preferable are resins that satisfy a bending elastic modulus of 3000 Mpa or more and a glass transition temperature Tg of 300°C or higher.

[0015] The thickness of the resin tube is not limited in particular, but is preferably the above 10 to 100 µm, and more preferably 12 to 50 µm.

[0016] Examples of means for forming the resin tube can include a resin tube formed by winding a resin film, although not limited thereto in particular.<3> Antenna Element

[0017] Examples of material that an antenna element having a helical pattern is made of include metals such as copper, aluminum, silver, and so forth (including alloys of each), although not limited thereto in particular.

[0018] The antenna element in the above means [1] or [2] includes the following forms. (a) A form in which there is one antenna element having a predetermined helical pattern (b) A form in which there is a plurality of antenna elements having the same helical pattern (c) A form in which there is one each of antenna elements having helical patterns that are different from each other. (d) A form in which there is a plurality each of antenna elements having helical patterns that are different from each other. (e) A form in which antenna elements having helical patterns that are different from each other are a combination of one thereof and a plurality of others.

[0019] The antenna elements in the above means [7] include the following forms. (f) A form in which there is one each of a first antenna element and a second antenna element (g) A form in which there is a plurality of each of the first antenna element and of the second antenna element (h) A form in which the first antenna element and the second antenna element are a combination of one thereof and a plurality of others.

[0020] Examples of means for forming the antenna elements include the following forms, although not limited thereto in particular. (k) An antenna element formed by plating, sputtering, metallizing processing, printing, or the like, of metal upon a resin film for a resin tube. (l) An antenna element in which a metal foil is bonded to a resin film for a resin tube by an adhesive. (m) An antenna element formed by plating, sputtering, metallizing processing, printing, or the like, of metal upon a dielectric core <4> Joining

[0021] Examples of means for joining the resin tube and the dielectric core include joining (bonding) by an adhesive, fusing, thermal compression, joining with a spacer such as a sponge, wedge, or the like, swaging, and tightening by screws, and so forth, although not limited thereto in particular. Joining (bonding) using an adhesive is preferable in terms of good adhesion and sealing properties, and is particularly preferable in terms of easy joining in a case in which the resin tube is made of polyimide. The adhesive is not limited in particular, but double-sided adhesive tape is preferred due to good bonding workability.

[0022] The means for joining the antenna element and the dielectric core are not limited in particular, but in the above form (m), examples include joining by plating, sputtering, metallization processing, printing, and so forth, and in the above forms (k) and (l), examples include joining (bonding) by adhesive. The adhesive is not limited in particular, but double-sided adhesive tape is preferred due to good bonding workability.

[0023] The means for joining the antenna element and the resin tube are not limited in particular, but in the above forms (k) and (l), examples include joining by plating, sputtering, metallization processing, printing, and so forth, and in the above form (m), examples include joining (bonding) by adhesive. The adhesive is not limited in particular, but double-sided adhesive tape is preferred due to good bonding workability.<5> Applications

[0024] Applications of the helical antenna according to the present invention are not limited in particular, and can be suitably used in various types of communication equipment (including information equipment) that perform reception, transmission, or both, of radio waves.

[0025] The communication equipment may be fixed communication equipment, but mobile communication equipment is suitable due to the ability to take advantage of the smallness of the present invention.

[0026] Examples of mobile communication equipment include mobile communication equipment (transceivers, mobile information terminals, mobile phones, and so forth), in-vehicle communication equipment (automotive navigation systems, in-vehicle information terminals, in-vehicle telephones, and so forth), drone-mounted communication equipment, and so forth.

[0027] Examples of the communication content include GPS data, general data, phone calls, and so forth, although not limited thereto in particular.Embodiment

[0028] An embodiment by which the present invention is carried out will be described below with reference to the drawings. Note that the materials, quantities, and conditions of each part in the embodiment are merely illustrative, and can be modified as appropriate without departing from the spirit of the invention.

[0029] An antenna device according to an embodiment illustrated in FIG. 1 to FIG. 5B 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.

[0030] A key feature of the helical antenna 1 is that, as illustrated in FIGS. 5A and 5B and so forth, a dielectric core 2 that is columnar, antenna elements 3 and 4 that have helical patterns, and a resin tube 5, are disposed in that order from inside to outside, and the resin tube 5 is joined by an adhesive to an outer peripheral face of the dielectric core 2 in a vicinity at which the antenna elements are covered thereby.

[0031] In other words, the helical antenna 1 includes the dielectric core 2 that is columnar, the antenna elements 3 and 4 that have helical patterns and that are joined to the outer peripheral face of the dielectric core 2, and the resin tube 5 joined to outer side faces of the antenna elements 3 and 4 and also joined to the outer peripheral face of the dielectric core 2 by an adhesive.

[0032] The helical antenna 1 will be described in detail below.

[0033] The dielectric core 2 is made of a ceramic material (main component: MgO-TiO 2 ) with a relative permittivity of 21, and is formed into a columnar shape with a length of 18 mm and an outer diameter of 14 mm. Although the dielectric core 2 that is illustrated has a through hole at an axial center thereof, this through hole may be omitted. This is because, as will be described later, the helical antenna 1 according to the present embodiment is of an end-fire type. However, when changing to a back-fired type, a through hole is required to pass a transmission line through.

[0034] The resin tube 5 is formed by winding a resin film 6 made of polyimide having a thickness of 20 µm into a cylindrical shape with a length of 23 mm and an inner diameter of 15 to 16 mm. That is to say, the resin tube 5 is longer than the dielectric core 2. Lower end levels of the dielectric core 2 and the resin tube 5 are aligned, and the resin tube 5 extends further upward than the dielectric core 2. The polyimide that is used has a bending elastic modulus (JIS K 7171:2022, test conditions 2 mm / min) of 3500 Mpa and a glass transition temperature Tg (JIS K 7121:2012) of 335°C.

[0035] The antenna elements 3 and 4 include first antenna elements 3 which are relatively short in accordance with the length of the dielectric core 2, and second antenna elements 4 which are relatively long in accordance with the length of the resin tube 5, and inside of a portion of the second antenna elements 4 that protrudes beyond the dielectric core 2 is an air region (air core) . The first antenna elements 3 and the second antenna elements 4 are each made of copper foil with a line width of 1 mm and a thickness of 35 µm, four of each being provided, which are disposed alternately at intervals in a peripheral direction.

[0036] The resin tube 5 and the antenna elements 3 and 4 are joined to the outer peripheral face of the dielectric core 2 by double-sided adhesive tape 7.

[0037] As illustrated in FIGS. 2A, 2B, and 2C, the resin film 6 forming the resin tube 5, the antenna elements 3 and 4, and the double-sided adhesive tape 7 are assembled in advance. As illustrated in FIG. 2A, the resin film 6 has a parallelogram shape in front view. As illustrated in FIG. 2B, the first antenna element 3 and the second antenna element 4 are joined to an inner face of the resin film 6 by an adhesive (solvent-soluble polyimide varnish (PIAD)), and as illustrated in FIG. 2C, the double-sided adhesive tape 7 is further bonded thereto to form an assembly. The double-sided adhesive tape 7 that is used is, for example, No. 5605R, manufactured by Nitto Denko Corporation (50 µm-thick tape having an acrylic-based adhesive applied to both sides of polyester film).

[0038] The resin film 6 is flat in FIG. 2B, but in FIG. 2C tends to be pulled by the double-sided adhesive tape 7 and to be deformed so as to surround the antenna elements 3 and 4.

[0039] The double-sided adhesive tape is omitted at portions indicated by hatching in FIG. 2A, i.e., at each end portion of the antenna elements 3 and 4, so as to be exposed for soldering, which will be described later.

[0040] Then, as illustrated in FIG. 1, FIGS. 3A, 3B, and 3C, FIGS. 5A and 5B, and so forth, this assembly is wound around the outer peripheral face of the dielectric core 2 to form the resin tube 5, and also the resin tube 5 is joined to the outer peripheral face of the dielectric core 2 by a pressure-sensitive adhesion agent (the adhesive) of the double-sided adhesive tape 7, in the vicinity at which the antenna elements are covered thereby, with the antenna elements 3 and 4 also being joined to the outer peripheral face of the dielectric core 2 by the same pressure-sensitive adhesion agent.

[0041] Upper end portions of the four first antenna elements 3 are soldered to a first connecting conductor 8 that is formed in a cross pattern by metallization processing on an upper end face of the dielectric core 2 (indicted by dots in FIG. 3A), thereby forming a closed circuit.

[0042] Upper end portions of the four second antenna elements 4 are soldered to a second connecting conductor 9 made of a cross - shaped metal plate that is placed on an upper end of the resin tube 5 (indicated by dots in FIG. 3B), thereby forming a closed circuit.

[0043] A lower end portion of each of the antenna elements 3 and 4 is soldered to a feeding point 11 of the connection board 10 that is placed on the upper end of the resin tube 5 (indicated by dots in FIG. 3C). That is to say, the antenna system of the helical antenna 1 according to the present embodiment is an end-fire type.

[0044] The helical antenna 1 according to the present embodiment configured as described above has the following functions and effects. (1) The resin tube 5 protects the antenna elements 3 and 4 from being exposed to air, dust, colliding objects, and so forth, and the helical antenna 1 has improved rust-proof properties, dust-proof properties, and scuff-proof properties, and is highly durable. (2) The antenna elements 3 and 4 are joined to the outer peripheral face of the dielectric core 2 by an adhesive, and accordingly protection of the antenna elements 3 and 4 is improved. (3) The resin tube 5 is formed by winding the resin film 6, and accordingly the resin tube 5 can be easily formed. (4) The configuration has the assembly wound around the outer peripheral face of the dielectric core 2, and accordingly the helical antenna 1 can be easily manufactured. (5) The first antenna element 3 that is relatively short and the second antenna element 4 that is relatively long are compatible with a plurality of frequencies (e.g., 1575.42 MHz, 1227.6 MHz). (6) The inner side of the portion of the second antenna element 4 that protrudes beyond the dielectric core 2 is an air region (air core), and accordingly the weight thereof can be reduced, or alternatively, another dielectric core 2 can be provided to adjust the frequency. (7) The resin tube 5 is made of polyimide, and accordingly rigidity thereof is improved, and the air region can be easily formed. Also, heat resistance during soldering or the like of the antenna elements 3 and 4 is improved. (8) The antenna system is an end-fire type, and accordingly there is no need to provide a transmission line that passes through the dielectric core 2. (9) The antenna elements 3 and 4 are closed circuits, and accordingly operational gain performance is improved. (10) Size and weight can be reduced even more than in Patent Document 2. (11) The number of parts is few, and costs can be reduced.

[0045] As illustrated in FIG. 1 and FIG. 4, in the helical antenna 1 according to the present embodiment, the antenna device can be configured by connecting the circuit board 12 having the amplifier to the connection board 10, and further providing the shielding case 13 for the circuit board 12, providing the connector 14 for connecting the coaxial cable, and so forth, as necessary. This helical antenna 1 or antenna device is small and lightweight and can be incorporated into the various types of communication equipment mentioned above.

[0046] Note that the present invention is not limited to the above embodiment, and can be carried out modified as appropriate without departing from the spirit and scope of the invention. (1) The first antenna elements 3 may be directly formed on the outer peripheral face of the dielectric core 2 by plating, sputtering, metallization processing, printing, or the like, with just the second antenna elements 4 being provided on the resin tube 5 as in the embodiment above, as in the modification illustrated in FIGS. 6A and 6B. However, the manufacturing efficiency of the embodiment above is better. (2) Changing the antenna system to an end-fire type. (3) Changing the antenna elements 3 and 4 to open circuits. Description of the Reference Numerals

[0047] 1Helical antenna 2Dielectric core 3First antenna element 4Second antenna element 5Resin tube 6Resin film 7Double-sided adhesive tape 8First connecting conductor 9Second connecting conductor 10Connection board 11Feeding point 12Circuit board 13Shielding case 14Connector

Claims

1. A helical antenna, wherein a dielectric core that is columnar in shape, an antenna element that has a helical pattern, and a resin tube, are disposed in that order from inside to outside, and the resin tube is joined to an outer peripheral face of the dielectric core in a vicinity at which the antenna element is covered.

2. A helical antenna, comprising a dielectric core that is columnar in shape, an antenna element that has a helical pattern and that is joined to an outer peripheral face of the dielectric core, and a resin tube that is joined to an outer side face of the antenna element and that is also joined to the outer peripheral face of the dielectric core.

3. The helical antenna according to claim 1 or 2, wherein the antenna element is joined to the outer peripheral face of the dielectric core by 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. The helical antenna according to claim 5, wherein the resin tube is formed by an assembly of the resin film, the antenna element joined to an inner face of the resin film, and a double-sided adhesive tape that covers the antenna element and that is bonded to the inner face of the resin film is wound around the outer peripheral face of the dielectric core, and also the resin tube is joined to the outer peripheral face of the dielectric core by an adhesive of the double-sided adhesive tape.

7. The helical antenna according to claim 1 or 2, wherein the resin tube is longer than the dielectric core, the antenna element includes a first antenna element that is relatively short in accordance with a length of the dielectric core, and a second antenna element that is relatively long in accordance with a length of the resin tube, and inside of a 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 bending elastic modulus (JIS K 7171:2022, test conditions 2 mm / min) of 2500 Mpa or more and a glass transition temperature Tg (JIS K 7121:2012) of 220°C or higher.

9. The helical antenna according to claim 1 or 2, wherein an antenna system 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, comprising the helical antenna according to claim 1 or 2, a connection board having a feeding point to the helical antenna, and a circuit board having an amplifier connected to the connection board.

12. Communication equipment in which is incorporated the helical antenna according to claim 1 or 2.

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