JP4780352B2 - Antenna device - Google Patents

Description

  The present invention relates to an antenna device, and more particularly to an antenna device used in a frequency band of a wireless local area network (LAN).

  As is well known in this technical field, a wireless LAN refers to a LAN that uses a transmission path other than a wired cable, such as radio waves and infrared rays.

  The standardization of the wireless LAN is formulated by the 802.11 committee of the IEEE (American Institute of Electrical and Electronics Engineers). That is, the IEEE 802.11 committee has established standards and specifications for wireless LAN standards.

  For example, IEEE 802.11a is a 5 GHz band high-speed wireless LAN / wireless access standard established by the IEEE 802.11 committee. The communication speed (transfer speed) is about 20 to 50 Mbit / second. As MAC (medium access control), CSMA / CD (carrier sense multiple access with collision detection) is adopted. The modulation method of the physical layer is OFDM (Orthogonal Frequency Division Multiplexing).

  On the other hand, IEEE 802.11b is a wireless LAN specification standardized in September 1999 by the IEEE 802.11 committee. In IEEE 802.11b, a frequency in the 2.4 GHz band is used, and direct spreading (DS) is used as a modulation method. The transmission rate (transfer rate) is 11 Mbit / sec and 5.5 Mbit / sec.

  Furthermore, IEEE 802.11g is one of the wireless LAN standards established in June 2003 by the IEEE 802.11 committee, and is a specification that performs communication of about 54 Mbit / s in the 2.4 GHz band. . OFDM is adopted as the modulation method. Therefore, IEEE 802.11g uses the same 2.4 GHz band frequency as IEEE 802.11b, and supports a transfer rate of 54 Mbit / s, which is about five times that of IEEE 802.11b. Unlike IEEE 802.11a, which also supports a transfer rate of 54 Mbit / s, IEEE 802.11g is also compatible with IEEE 802.11b. The maximum transfer rate of 54 Mbit / s is exactly the same as that of IEEE 802.11a, but the 2.4 GHz band is a “congested” frequency band that is used in many devices other than wireless LAN. For this reason, it is said that the actual transfer rate in IEEE 802.11g is slower than that in IEEE 802.11a.

  As described above, since IEEE 802.11b and IEEE 802.11g use the same frequency band (2.4 GHz band), both are collectively referred to as IEEE 802.11b / g.

  Various antenna devices used in such a wireless LAN frequency band have been known.

  For example, Patent Document 1 discloses an antenna device having a resonance frequency of 2.456 GHz. Patent Document 1 discloses an antenna device in which an antenna pattern (conductor pattern) is formed on a main surface (front surface, first surface) of a substrate in FIG. Specifically, the antenna device disclosed in Patent Document 1 includes a first L-shaped wiring pattern, a second L-shaped wiring pattern, and an antenna pattern (conductor pattern) formed on the main surface of the substrate. It has an L-shaped ground pattern and an L-shaped signal pattern, and is generally U-shaped. The leading end of the first L-shaped wiring pattern and the leading end of the second L-shaped wiring pattern are spaced apart from each other. The second L-shaped wiring pattern is formed substantially symmetrically with the first L-shaped wiring pattern. One end of the L-shaped ground pattern is electrically connected to the tip of the first L-shaped wiring pattern. The L-shaped ground pattern is formed along the second L-shaped wiring pattern with an interval inside the second L-shaped wiring pattern. One end of the L-shaped signal pattern is electrically connected to the tip of the first L-shaped wiring pattern. The L-shaped signal pattern is formed along the L-shaped ground pattern with a space inside the L-shaped ground pattern. The antenna device further includes a coaxial cable having a center conductor and an outer conductor. At the tip of the coaxial cable, the center conductor is connected to the other end of the L-shaped signal pattern, and the outer conductor is connected to the other end of the L-shaped ground pattern.

  Anyway, Patent Document 1 includes a substrate having a main surface, an antenna pattern (transmission / reception pattern) formed on the main surface for transmitting and receiving a radio signal (radio wave) in a predetermined frequency band, and a coaxial cable. An antenna device is disclosed.

  On the other hand, Patent Document 2 discloses a flat antenna that has good antenna input impedance and enables efficient operation as an antenna even when a metal casing or a metal part is in the vicinity. Patent Document 2 discloses a flat antenna in which good impedance matching is performed in a frequency band of 2.4 GHz. Specifically, the flat antenna disclosed in Patent Document 2 includes a printed circuit board made of a dielectric, a first antenna radiating element that is one radiating element of a dipole antenna, and the other radiating element of a dipole antenna. A second antenna radiating element, a parasitic element formed of a conductor pattern, a microstrip line serving as a power feeding line ancestor of a radio wave, and a ground conductor forming a ground side of the feeding line. The first antenna radiating element, the parasitic element, and the microstrip line are formed on one surface (front surface, first surface) of the printed board by a conductor pattern. The second antenna radiating element and the ground conductor are formed by a conductor pattern on the other surface (back surface, second surface) of the printed circuit board. A dipole antenna is configured by feeding a high-frequency signal tail from the end of the microstrip line. The first antenna element and the microstrip line are connected substantially at the center. The parasitic element may be omitted. The central conductor of the coaxial cable is connected to a power feeding portion formed on the printed circuit board, and the outer conductor of the coaxial cable is fixed to a metal fitting soldered to a ground conductor formed on the printed circuit board.

  Anyway, Patent Document 2 discloses a printed circuit board having first and second surfaces (front and back surfaces) facing each other, and a radio signal (radio wave) in a predetermined frequency band formed on the first and second surfaces. A flat plate antenna (antenna device) including a conductor pattern (transmission / reception pattern) for transmitting and receiving and a coaxial cable is disclosed.

  Patent Document 3 discloses a printed circuit board antenna in which antenna and balun patterns are formed on a double-sided or single-sided printed board. In Patent Document 3, a dipole antenna pattern and a balun coaxial tube fixing pattern are formed on a first surface (front surface) of a printed circuit board, and a branch conductor pattern is formed on a second surface (back surface) of the printed circuit board or It is formed on the first surface. The center line of the coaxial tube is soldered to the feeding point of the dipole antenna, and the outer conductor of the coaxial tube is soldered to the feeding point of the dipole antenna and the branch conductor pattern. The antenna and balun disclosed in Patent Document 3 are incorporated in a casing of a portable wireless device, and are used with a frequency band of 421 MHz to 440 MHz.

  Anyway, Patent Document 3 discloses a printed circuit board having first and second surfaces (front and back surfaces) facing each other and a predetermined frequency formed on the first and second surfaces (or first surface). A printed circuit board antenna including an antenna pattern portion (transmission / reception pattern) for transmitting and receiving a band radio signal (radio wave) and a coaxial tube (coaxial cable) is disclosed.

  Further, Patent Document 4 discloses a plane polarized antenna that can be easily downsized and mounted. The plane polarized antenna disclosed in Patent Document 4 includes a flat plate insulating substrate and a conductor portion provided on the flat plate insulating substrate. The conductor portion includes an inverted F antenna portion having a feeding point and a ground surface portion. The core wire (center conductor) of the coaxial cable is connected to the feeding point of the inverted F antenna portion, and the ground wire (external conductor) of the coaxial cable is connected to the ground plane portion.

  The antenna devices disclosed in Patent Documents 1 to 4 described above are called “substrate antennas” because the antenna pattern is formed on the substrate.

  On the other hand, Patent Document 5 discloses a broadband and high gain antenna. The antenna disclosed in Patent Document 5 is formed with an antenna element provided with at least one bent portion, a ground portion to which one end of the antenna element is connected, and a direction in which the inner angle of the bent portion is divided from the bent portion. It has a feed part and a feed line connected to this feed part. An inner conductor of a coaxial cable that is a feed line is connected to the feed section. The outer conductor of the coaxial cable is connected to the ground portion. When manufacturing an antenna, for example, a flat plate made of phosphor bronze or the like is pressed to form a conductive flat plate in which a power feeding portion is provided in the antenna element, the ground portion, and the bent portion of the antenna element. An antenna using such a conductive flat plate is called a “sheet metal antenna”.

Japanese Patent Laying-Open No. 2006-50517 (FIG. 8) JP 2005-79867 A JP-A-6-188610 JP 2008-187631 A JP 2007-159064 A

  As described above, each of the antenna devices (substrate antennas) disclosed in Patent Documents 1 to 4 forms a pattern on a substrate (printed substrate). Since the printed circuit board is expensive, the antenna device is also expensive.

  On the other hand, Patent Document 5 only describes that the outer conductor of the coaxial cable is connected to the ground portion, and does not disclose how to connect (fix) the outer conductor of the coaxial cable. As is well known in the art, the outer conductor of the coaxial cable is composed of a net-like conductor. When the outer conductor (mesh conductor) of the coaxial cable is connected to the ground portion only by soldering, there is a problem that it is difficult to solder. In addition, in the electrical connection only by soldering, there is a problem that assembly is difficult and the mounting strength of the coaxial cable is weak. Furthermore, there is a problem that the cost of soldering is high.

  Accordingly, an object of the present invention is to provide an antenna device (sheet metal antenna) that can be easily assembled.

  Another object of the present invention is to provide an antenna device (sheet metal antenna) that can improve the mounting strength of a coaxial cable.

  Still another object of the present invention is to provide an inexpensive antenna device (sheet metal antenna).

According to the present invention, an antenna device ( 10A ) capable of transmitting and receiving radio waves in a predetermined frequency band, the coaxial having a center conductor (22), an outer conductor (21), and a sheath (24) covering the outer conductor. In the antenna device ( 10A ) having the cable (20) and the antenna element ( 30A ), the antenna element ( 30A ) includes an antenna pattern portion ( 32A ) and a ground portion integrally formed with the antenna pattern portion. ( 34A ), the coaxial cable (20) is caulked and fixed to the ground part ( 34A ), and the antenna element (30A) extends from the ground part (34A). The caulking portion (342A) taken out and the additional caulking portion (344A) extending from the caulking portion are provided, and the outer conductor (21) is connected to the caulking portion (3 2A) are caulked, the sheath (24) is, the additional crimping portion (344A) is fixed by caulking, the antenna device (10A) is obtained.

  In the antenna apparatus, the predetermined frequency band may be a 2.4 GHz band frequency, for example. The metal plate is preferably made of phosphor bronze. The antenna pattern unit may be composed of an inverted F antenna, for example. In this case, the central conductor of the coaxial cable is connected to the feeding portion of the inverted F antenna.

  In addition, the code | symbol in the said parenthesis is attached | subjected in order to make an understanding of this invention easy, and it is only an example, and of course is not limited to these.

  In the antenna device according to the present invention, since the coaxial cable is caulked and fixed to the ground portion of the antenna element, it can be easily assembled, the mounting strength of the coaxial cable can be improved, and an inexpensive antenna device (sheet metal antenna) can be obtained. Can be provided.

1 is a plan view of an antenna device (sheet metal antenna) according to a first embodiment of the present invention. It is the principal part enlarged plan view (a) and principal part enlarged side view (b) which expanded and showed a part (main part) of the antenna apparatus (sheet-metal antenna) enclosed with the broken-line circle | round | yen of FIG. (A) And (B) is a figure which shows the state which crimps and fixes the outer conductor of a coaxial cable to a ground part by a raising part, (A) is sectional drawing which shows the state before crimping, (B ) Is a cross-sectional view showing a state after crimping, and (C) and (D) are diagrams showing a state in which the sheath of the coaxial cable is caulked and fixed to the ground portion by an additional cut and raised portion, It is sectional drawing which shows the state before crimping, (D) is sectional drawing which shows the state after crimping. It is a top view of the antenna device which concerns on the 2nd Embodiment of this invention. It is the principal part enlarged plan view (a) and principal part enlarged side view (b) which expanded and showed a part (main part) of the antenna apparatus (sheet-metal antenna) enclosed with the broken-line circle | round | yen of FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An antenna apparatus (sheet metal antenna) 10 according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view of an antenna device (sheet metal antenna) 10. 2 (a) and 2 (b) are an enlarged plan view and an enlarged view of an essential part of a part (main part) of an antenna device (sheet metal antenna) 10 surrounded by a broken-line circle in FIG. It is a side view.

  1 and 2, an orthogonal coordinate system (X, Y, Z) is adopted. In the state shown in FIGS. 1 and 2, the X axis is the front-rear direction (depth direction), the Y axis is the left-right direction (width direction, lateral direction), and the Z axis is the up-down direction (height direction). .

  The illustrated antenna device (sheet metal antenna) 10 is for transmitting and receiving radio waves in a predetermined frequency band. In the illustrated example, the predetermined frequency band is a frequency in the 2.4 GHz band used in IEEE 802.11b / g.

  The illustrated antenna device (sheet metal antenna) 10 includes a coaxial cable 20 and an antenna element 30.

  As shown in FIG. 2, the coaxial cable 20 is a coaxial-shaped electric signal transmission medium including a cylindrical outer conductor 21 and a central conductor 22 at the center thereof. The outer conductor 21 and the center conductor 22 are insulated by a cylindrical insulator 23. The outer conductor 21 is covered with a sheath (outer skin). The outer conductor 21 is also called a ground wire or an outer conductor, and is made of a net-like conductor as shown in FIG. The center conductor 22 is also called a core wire or an inner conductor.

  As shown in FIG. 1, the coaxial cable 20 extends in the front-rear direction (X-axis direction). The front end portion of the coaxial cable 20 is cut as shown in FIG. 2, and the center conductor 22, the insulator 23, and the outer conductor 21 are exposed.

  The antenna element 30 is formed by pressing a flat metal plate having a main surface (surface, upper surface) 30u. The metal plate before pressing has a substantially rectangular parallelepiped (rectangular plate) shape having a length (length) B, a width (width) W, and a thickness (height) T. In the illustrated example, the length (length) B is 24 mm, the width (width) W is 22 mm, and the thickness (height) T is 0.15 mm. In the illustrated example, the metal plate is made of phosphor bronze that has not been plated.

  The antenna element 30 includes an antenna pattern portion 32 and a ground portion 34 formed integrally with the antenna pattern portion 32. In the illustrated example, the antenna pattern unit 32 is configured by an inverted F antenna. The inverted F antenna 32 includes an L-shaped L-shaped portion 322 and a power feeding portion 324 protruding from the L-shaped portion 322. The L-shaped portion 322 has a long side extending in the lateral direction (Y-axis direction) and a short side extending in the front-rear direction (X-axis direction). The ground portion 34 has a substantially rectangular shape.

  The center conductor 22 of the coaxial cable 20 is electrically connected to the power feeding portion 324 of the antenna pattern portion (inverted F antenna) 32 by soldering 50.

  The coaxial cable 20 is caulked and fixed to the ground portion 34 as will be described later.

  Specifically, the ground part 34 is formed with a cut and raised part 342 and an additional cut and raised part 344. The outer conductor 21 of the coaxial cable 20 is caulked and fixed to the ground part 34 by a cut and raised part 342. The sheath 24 of the coaxial cable 20 is caulked and fixed to the ground portion 34 by an additional cut and raised portion 344.

  3A and 3B are views showing a state in which the outer conductor 21 of the coaxial cable 20 is cut and raised and fixed to the ground portion 34 by the portion 342. FIG. 3A is a cross-sectional view showing a state before crimping, and FIG. 3B is a cross-sectional view showing a state after crimping.

  3C and 3D are views showing a state in which the sheath 24 of the coaxial cable 20 is caulked and fixed to the ground portion 34 by the additional cut and raised portion 344. FIG. FIG. 3C is a cross-sectional view showing a state before caulking, and FIG. 3D is a cross-sectional view showing a state after caulking.

  Thus, since the coaxial cable 20 is caulked and fixed to the ground portion 34, the attachment strength of the coaxial cable 20 can be improved. In addition, since it is caulking, assembly is easier and cost is lower than soldering.

  The outer conductor 21 of the coaxial cable 20 may be soldered to the ground part 34.

  In the illustrated example, an additional cut and raised portion 344 is formed in the ground portion 34, and the sheath 24 of the coaxial cable 20 is caulked and fixed to the ground portion 34 by the additional cut and raised portion 344. The part 344 is not essential and may be omitted.

  A pair of mounting holes 346 for mounting the antenna device 10 to a housing (not shown) are formed in the illustrated ground portion 34.

  An antenna device (sheet metal antenna) 10A according to a second embodiment of the present invention will be described with reference to FIG. 4 and FIG. FIG. 4 is a plan view of the antenna device (sheet metal antenna) 10A. 5 (a) and 5 (b) are an enlarged plan view and an enlarged view of a main part of a part (main part) of an antenna device (sheet metal antenna) 10A surrounded by a broken-line circle in FIG. It is a side view.

  4 and 5, an orthogonal coordinate system (X, Y, Z) is adopted. In the state shown in FIGS. 4 and 5, the X-axis is the front-rear direction (depth direction), the Y-axis is the left-right direction (width direction, lateral direction), and the Z-axis is the up-down direction (height direction). .

  The illustrated antenna device (sheet metal antenna) 10A is similar to the antenna device (sheet metal antenna) 10 shown in FIGS. 1 and 2 except that the configuration of the antenna element is different from that shown in FIGS. It has the same configuration. Therefore, the reference numeral 30A is attached to the antenna element. Components having the same functions as those shown in FIGS. 1 and 2 are denoted by the same reference numerals, and only differences will be described in detail below for the sake of simplicity.

  The illustrated antenna device (sheet metal antenna) 10A is for transmitting and receiving radio waves in a predetermined frequency band. In the illustrated example, the predetermined frequency band is a frequency in the 2.4 GHz band used in IEEE 802.11b / g.

  Similarly to the antenna element 30, the antenna element 30A is formed by pressing a flat metal plate having a main surface (surface, upper surface) 30u. The metal plate before pressing has a substantially rectangular parallelepiped (rectangular plate) shape having a length (length) B, a width (width) W, and a thickness (height) T. In the illustrated example, the length (length) B is 24 mm, the width (width) W is 22 mm, and the thickness (height) T is 0.15 mm. In the illustrated example, the metal plate is made of phosphor bronze that has not been plated.

  The antenna element 30A includes an antenna pattern portion 32A and a ground portion 34A integrally formed with the antenna pattern portion 32A. In the illustrated example, the antenna pattern portion 32A is composed of an inverted F antenna. The inverted F antenna 32A has an L-shaped L-shaped portion 322A and a power feeding portion 324 protruding from the L-shaped portion 322A. The L-shaped portion 322A has a long side extending in the horizontal direction (Y-axis direction) and a short side extending in the front-rear direction (X-axis direction). The tip of the L-shaped portion 322A is bent at a right angle in a direction approaching the ground portion 34A. The ground portion 34A has a substantially rectangular shape, but has a rectangular opening 34Aa.

  The center conductor 22 of the coaxial cable 20 is electrically connected to the power feeding portion 324 of the antenna pattern portion (inverted F antenna) 32A by soldering 50.

  As will be described later, the coaxial cable 20 is caulked and fixed to the ground portion 34A.

  More specifically, the antenna element 30A includes a caulking portion 342A extending from the ground portion 34A and an additional caulking portion 344A extending from the caulking portion 342A through the rectangular opening 34Aa. The outer conductor 21 of the coaxial cable 20 is caulked and fixed by a caulking portion 342A. The sheath 24 of the coaxial cable 20 is fixed by caulking with an additional caulking portion 344A.

  Thus, since the coaxial cable 20 is caulked and fixed to the ground portion 34A, the mounting strength of the coaxial cable 20 can be improved. In addition, since it is caulking, assembly is easier and cost is lower than soldering.

  The outer conductor 21 of the coaxial cable 20 may be soldered to the ground portion 34A.

  Although the present invention has been described above with reference to preferred embodiments, it is needless to say that the present invention is not limited to the above-described embodiments. For example, the antenna pattern portion is not limited to the inverted F antenna of the above-described embodiment, and it is needless to say that antenna pattern portions having various shapes may be employed. In the embodiment described above, phosphor bronze is used as the material of the metal plate, but the material of the metal plate is not limited to this.

10, 10A antenna device (sheet metal antenna)
20 Coaxial cable (feed line)
21 Outer conductor 22 Central conductor 23 Insulator 24 Sheath
30, 30A Antenna element 30u Main surface (upper surface, front surface)
32, 32A Antenna pattern portion 322, 322A L-shaped portion 324 Power feeding portion 34, 34A Ground portion 342 Cut-and-raise portion 342A Caulking portion 344 Additional cut-raising portion 344A Additional caulking portion

Claims (4)

An antenna device capable of transmitting and receiving radio waves in a predetermined frequency band, wherein the antenna device includes a coaxial cable having a center conductor, an outer conductor, and a sheath covering the outer conductor, and an antenna element.
The antenna element is composed of a metal plate having an antenna pattern portion and a ground portion integrally formed with the antenna pattern portion,
The coaxial cable is caulked and fixed to the ground part ,
The antenna element has a caulking portion extending from the ground portion, and an additional caulking portion extending from the caulking portion,
The outer conductor is fixed by crimping at the crimping part,
An antenna device , wherein the sheath is fixed by caulking at the additional caulking portion .   The antenna device according to claim 1, wherein the predetermined frequency band is a frequency in a 2.4 GHz band.   The antenna device according to claim 1, wherein the metal plate is made of phosphor bronze. The antenna pattern part is composed of an inverted F antenna,
The central conductor of the coaxial cable is connected to the feeding portion of the inverted F antenna.
The antenna device according to any one of claims 1 to 3.

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