JP2008288931A - Antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna system providing a high antenna gain by increasing the loop area of a micro loop antenna. <P>SOLUTION: The antenna system 1 has the micro loop antenna 3, a circuit board 2, and a case 10 comprising resin-made case members 11 and 12 housing them. While a metal conductor 3a forming the micro loop antenna 3 is wired between joint surfaces of the case members 11 and 12 and the circuit board 2 is disposed inside the case members 11 and 12, a voltage is applied to the metal conductor 3a by an external voltage application device 20 to heat the metal conductor 3a and at the same time, the case members 11 and 12 are pressed against each other to be joined together. The micro loop antenna 3 is used as the metal conductor 3a used for the joining and then can be disposed near an external surface of the case 10 to obtain wide loop area, and the antenna system 1 can easily be manufactured with high waterproofness and sealing property. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an antenna device including a minute loop antenna used in a wireless communication device.

  For example, a portable wireless communication device that transmits and receives data using wireless communication may be desired to be as small as possible in order to improve portability, for example. For example, a micro loop antenna as shown in Non-Patent Document 1 is used. The micro loop antenna is obtained by reducing the total length of the loop antenna to about 1/10 or less of the transmission wavelength, and has a feature that it is more resistant to a noise electric field than the micro dipole antenna.

  By the way, the antenna gain of the minute loop antenna depends on the loop area of the minute loop antenna, and in order to increase the gain of the minute loop antenna, the loop area is generally enlarged. On the other hand, for example, in a portable wireless communication device, there is a strong demand for downsizing and thinning due to ease of portability and appearance design, and a minute loop antenna having a wide loop area is used for the antenna device. It was sometimes difficult.

Here, Patent Document 1 discloses an antenna device that can be easily manufactured by housing a micro loop antenna in an uneven portion of a housing joint surface and assembling the housing. In this antenna device, the antenna gain is improved by using a high dielectric constant material for the casing. However, Patent Document 1 does not disclose a method that can expand the loop area of the minute loop antenna. Further, this structure is configured so that the housing can be disengaged. For example, when a waterproof performance or a sealing performance is required for the housing fitting, a seal or the like is applied to the joint surface. A process is required.
IEICE “Antenna Engineering Handbook” PP. 62-63 Ohmsha 1st edition issued on October 30, 1980 JP-A-8-130403

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an antenna device that can obtain a high antenna gain by expanding the loop area of a minute loop antenna and can be easily manufactured. .

  In order to achieve the above object, the invention of claim 1 includes a micro loop antenna, a circuit board to which the micro loop antenna is connected, and a resin case that houses the micro loop antenna and the circuit board. The case is joined in combination with each other, and at least two or more case members constituting the case and the joint surfaces of the plurality of case members are in contact with each other from the inner surface of the case, or the plurality of case members A metal conductor embedded in the case along each surface, the metal conductor generates heat when a voltage is applied to the metal conductor from the outside, and the joint surfaces of the case member are welded to each other. In the antenna device in which the minute loop antenna and the circuit board are accommodated by joining the case members to each other, Metal conductor being connected to said circuit board, after bonding of said case member is to use the metal conductor as the small loop antenna.

  According to a second aspect of the invention, in the first aspect of the invention, the metal conductor as the minute loop antenna is connected to the circuit board through a relay.

  According to the first aspect of the present invention, since the metal conductor used when joining the case members is used as the minute loop antenna, the loop area of the minute loop antenna can be made wider than that which can be accommodated in the case. The antenna gain can be improved. Further, since the metal conductor also serves as a minute loop antenna, the number of parts is reduced and the manufacturing cost is reduced. Furthermore, since the case members are welded together by applying a voltage to the metal conductor, the antenna device can be easily manufactured, and the waterproof property and the sealing property can be enhanced.

  According to the invention of claim 2, when the metal conductor generates heat, the relay can be turned off so that the metal conductor and the circuit board are not connected to each other. Sometimes it is possible to more reliably prevent an electrical or thermal influence on the circuit board.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. 1 and 2 show a basic configuration of an antenna device 1 using a minute loop antenna according to the present embodiment. The antenna device 1 includes a circuit board 2, a minute loop antenna 3 arranged so as to form a ring in substantially the same plane as the circuit board 2, a resin case 10 that accommodates the circuit board 2 and the minute loop antenna 3, and the like. It consists of On the circuit board 2, a power feeding circuit unit 4 that feeds power to the micro loop antenna 3, a main circuit unit 5 that generates a radio signal to be transmitted by the micro loop antenna 3, a power source 6 that supplies driving power to the main circuit unit 5, and the like Is provided. The power source 6 is, for example, a rechargeable battery or a dry battery that can be removed and replaced from the antenna device 1. For example, power is supplied from the power source 6 to the main circuit unit 5 via a switch 6a, and the antenna device 1 is thereby driven.

  As shown in FIG. 2, in the present embodiment, the case 10 is constituted by two case members 11 and 12 having openings capable of accommodating the circuit board 2. The case 10 is configured so that the openings of the case members 11 and 12 are aligned and joined together to form a rectangular parallelepiped box that can accommodate the circuit board 2 therein. In a state where the two case members 11 and 12 are joined to each other, the minute loop antenna 3 and the circuit board 2 are accommodated in the case 10 so as not to be exposed to the outside.

  In the present embodiment, the micro loop antenna 3 includes, for example, a metal conductor 3a that is a conductive heating wire, a circuit connection line 3b that connects the metal conductor 3a and the power feeding circuit unit 4, and a circuit on the power feeding circuit unit 4. It consists of The metal conductor 3 a is disposed along the joint surfaces of the case members 11 and 12. The metal conductor 3a is embedded in the case 10 in a state where the case members 11 and 12 are joined. As shown in the figure, a part of the metal conductor 3a embedded in the case 10 in the vicinity of the feeder circuit portion 4 is interrupted, and two circuit connection lines 3b are wired near each end of the metal conductor 3a. Has been. The metal conductor 3a is connected to the power feeding circuit unit 4 through the circuit connection line 3b. The power supply circuit unit 4 is provided with a capacitor 7 having a predetermined capacitance, and the capacitor 7, the metal conductor 3a, and the circuit connection line 3b constitute a closed circuit loop. Most of the minute loop antenna 3 is composed of a metal conductor 3a, and the minute loop antenna 3 functions as an antenna when power is supplied to the loop from the main circuit unit 5. The loop of the minute loop antenna 3 is connected to the ground pattern 4 a provided on the circuit board 2 by the power feeding circuit unit 4, and the minute loop antenna 3 is grounded.

  If the frequency of wireless communication is f0, a signal of frequency f0 is output from the main circuit unit 5, and the micro loop antenna 3 is designed so that the total length of one loop is 1/10 of the transmission wavelength λ0. The impedance is adjusted so that the decrease of the antenna gain becomes small at the frequency f0 (= 2π / λ0). Specifically, the resonance frequency of the minute loop antenna 3 can be adjusted by appropriately selecting the capacitance of the capacitor 7.

  Here, in the present embodiment, the case members 11 and 12 can be joined by a known joining technique called so-called flat fusion (inner surface welding) using the metal conductor 3a of the minute loop antenna 3. Has been. Below, with reference to Fig.3 (a), (b), the joining procedure of the case members 11 and 12 is demonstrated.

  As shown in FIG. 3 (a), a groove portion 11a in which the metal conductor 3a can be embedded and a protrusion that protrudes so as to be able to fit in the groove portion 11a are provided on the joint surfaces of the case members 11 and 12, respectively. A portion 12a is formed. When joining the case members 11 and 12, first, the metal conductor 3 a is embedded in the groove 11 a of the case member 11, and the circuit board 2 is also disposed inside the case member 11. Next, the case member 12 is put on the case member 11 so that the protruding portion 12a fits into the groove portion 11a. At this time, as shown in FIG. 3B, the metal conductor 3a of the minute loop antenna 3 is arranged on the surface side of the case members 11 and 12 so that the conducting wire 3c serving as the end of the metal conductor 3a is exposed. Then, the circuit connection line 3b is connected and wired inside the portion where the conductive line 3c of the metal conductor 3a is exposed. Then, a predetermined voltage is applied to the conducting wire 3c exposed to the outside of the case members 11 and 12 by the external voltage applying device 20, and a current is passed through the metal conductor 3a to generate heat, while the arrow in FIG. As shown, the case members 11 and 12 are pressed toward each other. Thereby, the metal conductor 3a generates heat, the joint surfaces of the case members 11 and 12 are melted, the case members 11 and 12 are pressed against each other, and the metal conductor 3a on the joint surface of the case members 11 and 12 is provided. Are welded over the entire circumference without gaps, and the case member 11 and the case member 12 are joined. After the welding is completed, the conducting wire 3c is cut off at the surface of the case 10, for example, and the antenna device 1 is assembled as shown in FIG.

  At the time of welding, the metal conductor 3a generates heat to such an extent that the resin of the case members 11 and 12 is melted. However, the metal conductor 3a and the power feeding circuit portion 4 are separated from each other through the circuit connection line 3b. No adverse effect is caused on the circuit board 2. In addition, since the capacitor 7 is provided on the circuit board 2 and the welding current flows only in the closed circuit constituted by the metal conductor 3a and the conducting wire 3c, an electrical adverse effect on the circuit of the two circuit boards is provided. Does not occur. The welding may be performed with the power supply 6 removed or with the switch 6a turned off.

  Thus, in this embodiment, since the metal conductor 3a used for joining the case members 11 and 12 is used as the minute loop antenna 3, the minute loop antenna 3 is arranged in the vicinity of the outer surface of the case 10 and is placed inside the case 10. The loop area can be increased as compared with those that can be stored, and the antenna gain can be improved. In addition, the antenna device 1 having high waterproofness and airtightness at the joint surface of the case 10 can be easily assembled. In addition, since the number of parts can be reduced as compared with the case where the minute loop antenna and the metal conductor 3a used for joining are separately provided, the manufacturing cost of the antenna device 1 can be reduced.

  Further, when the antenna device is assembled by using the flat fusion joining method as described above, the minute loop antenna and the metal conductor 3a used for joining are made separate parts, and the metal conductor 3a surrounds the outside of the minute loop antenna. In such a case, mutual coupling between the antenna element and the metal conductor 3a may occur, and the antenna gain may be reduced. However, in the present embodiment, since the minute loop antenna 3 and the metal conductor 3a used for bonding are shared, mutual coupling does not occur. Therefore, the antenna gain of the minute loop antenna 3 can be increased, and at the same time, the waterproofness and sealing performance of the antenna device 1 can be increased.

  Next, an antenna device according to a modification of the above embodiment will be described. 4A and 4B show an antenna device according to this modification. The antenna device 31 is provided with a relay 33a that is linked to the switch 6a between the circuit connection line 3b of the antenna device 1 and the power feeding circuit unit 4 described above.

  When the switch 6a is on and the power is supplied from the power source 6 to the main circuit unit 5, the relay 33a is connected to the circuit connection line 3b so as to form a loop of the minute loop antenna 3, as shown in FIG. When the power supply circuit unit 4 is connected and the switch 6a is off, the circuit connection line 3b and the power supply circuit unit 4 are disconnected. When the antenna device 31 is assembled, when the case members 11 and 12 are joined, as shown in FIG. 4B, the switch 6a is turned off, whereby the relay 33a is connected to the circuit connection line 3b, the power feeding circuit unit 4, and the like. A voltage is applied by the voltage application device 20 in a state in which is disconnected.

  Thus, in this antenna device 31, the metal conductor 3a of the minute loop antenna 3 and the circuit board 2 can be made to be in a state in which they are not connected to each other, and a current can be passed through the metal conductor 3a to generate heat. It is possible to more reliably prevent electrical or thermal influence on the power supply circuit section 4 and the main circuit section 5 on the substrate 2 side. Note that the relay 33a is not limited to the one linked to the switch 6a, and operates to form a loop of the minute loop antenna 3 in accordance with, for example, a battery as the power source 6 being set and the main circuit unit 5 being able to be driven. It may be provided to do.

  In addition, this invention is not limited to the structure of the said embodiment, A various deformation | transformation is possible suitably in the range which does not change the meaning of invention. For example, the case may be configured by combining three or more case members with each other. Moreover, even if the micro loop antenna is not embedded in the case, the micro loop antenna may be disposed so as to come into contact with the joint surfaces of the case members from the inner surface of the case. Even in such a case, similarly, it is possible to manufacture an antenna device having a high antenna gain, a high waterproof property, a high sealing property, and a low manufacturing cost by using a metal conductor used when joining the case member as a minute loop antenna. it can.

The top view which shows schematic structure of the antenna device which concerns on one Embodiment of this invention. Side sectional view of the device. (A) is a sectional side view showing when the case member of the apparatus is joined, (b) is a plan view showing a circuit configuration at the time of joining the case member. (A) is a top view which shows schematic structure of the antenna apparatus which concerns on the modification of the said embodiment, (b) is a top view which shows the circuit structure at the time of joining of the case member of the apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,31 Antenna apparatus 2 Circuit board 3 Micro loop antenna 3a Metal conductor 10 Case 11, 12 Case member 33a Relay

Claims (2)

A micro loop antenna, a circuit board to which the micro loop antenna is connected, and a resin case that houses the micro loop antenna and the circuit board,
The case is
At least two or more case members that are joined in combination with each other and constitute the case, and the mutual joining surfaces of the plurality of case members abut on each other from the inner surface of the case or on the mutual surfaces of the plurality of case members A metal conductor embedded in the case along the
When a voltage is applied to the metal conductor from the outside, the metal conductor generates heat, the joining surfaces of the case members are welded together, and the case members are joined to each other, whereby the minute loop antenna and the circuit In the antenna device that houses the board,
The antenna device, wherein the metal conductor is connected to the circuit board, and the metal conductor is used as the minute loop antenna after the case member is joined. The antenna device according to claim 1, wherein the metal conductor as the minute loop antenna is connected to the circuit board via a relay.

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