JP2014230129A - Portable transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the aesthetic quality while securing transmission characteristics of transmission radio waves.SOLUTION: A portable transmitter includes a housing 10 having a conductive member 10a where a slit 14 having an opening shape is formed. Power is fed to the conductive member 10a through first and second feeding points 100a, 100b provided at a peripheral part of the slit 14, and the conductive member 10a functions as an antenna which transmits radio waves.

Description

  The present invention relates to a portable transmitter that transmits radio waves for control to an in-vehicle device that controls vehicle equipment mounted on a vehicle.

  Conventionally, as an antenna for transmitting radio waves, a plurality of slits without open ends are formed by a narrow conductor, and a single feeding point is provided in the narrow conductor portion, and the inner conductor of the coaxial cable is provided at this feeding point. And the ground point on the ground plate is connected to the outer conductor of the coaxial cable so that the broadband element and the ground plate are not electrically connected (for example, see Patent Document 1). ).

JP 2006-14265 A

  By the way, in vehicles, vehicle door locking / unlocking systems that control locking and unlocking of vehicle doors using portable devices such as so-called smart keys and remote keys are widely used. In a portable device of such a vehicle door locking / unlocking system, a UHF band transmission signal is transmitted via an antenna arranged in a case of the portable device, such as a pattern antenna formed on a printed circuit board, for example. It is like that.

  In the portable device having such a configuration, in order to improve the designability, a metal member is added as a decoration to the case of the portable device, or a metal member is added as a decoration so as to surround the case of the portable device Can be considered.

  However, when such a metal member is added to the case of the portable device, transmission metal transmitted from the antenna arranged in the case of the portable device to the outside is shielded by the metal member. There arises a problem that the characteristics are remarkably deteriorated. For this reason, restrictions, such as restrict | limiting the metal member added to a portable machine to a part of case, will generate | occur | produce.

  The present invention has been made in view of the above problems, and an object of the present invention is to improve design properties while ensuring transmission characteristics of transmission radio waves.

  In order to achieve the above object, the invention described in claim 1 is a portable transmitter that transmits radio waves for control to an on-vehicle device (3) that controls vehicle equipment mounted on a vehicle (2). And a housing (10) having a conductive member (10a) in which an opening-shaped slit (14) is formed, and the conductive member is a first feeding point and a second feeding point provided at the peripheral edge of the slit. It is supplied with power via (100a, 100b) and functions as an antenna for transmitting radio waves.

  According to such a configuration, the housing (10) including the conductive member (10a) in which the opening-shaped slit (14) is formed is provided, and the conductive member is provided in the first peripheral portion of the slit. Since the power is fed through the second feeding points (100a, 100b) and functions as an antenna for transmitting radio waves, the design can be improved while ensuring the transmission characteristics of the transmission radio waves.

  In addition, the code | symbol in the bracket | parenthesis of each means described in this column and the claim shows the correspondence with the specific means as described in embodiment mentioned later.

1 is an external view of a portable transmitter according to an embodiment of the present invention. It is a disassembled perspective view of the portable transmitter which concerns on one Embodiment of this invention. It is a figure which shows the structure of the matching circuit of this portable transmitter. It is a figure for demonstrating the position of the 1st, 2nd feeding point. It is an example of the frequency characteristic of the reflection coefficient of a slit antenna. It is the figure shown about the modification.

  An external view of a portable transmitter according to an embodiment of the present invention is shown in FIG. An exploded perspective view of the portable transmitter is shown in FIG. The portable transmitter 1 includes a remote key that transmits radio waves, and an in-vehicle device 3 that receives radio waves from the remote keys and performs locking control and unlocking control of a door (corresponding to vehicle equipment) of the vehicle 2. It is used as a remote key of a vehicle door locking / unlocking system consisting of

  The portable transmitter 1 includes a housing 10 having a conductive member 10a in which an opening-shaped slit 14 is formed. In the portable transmitter 1 according to the present embodiment, the entire housing 10 is composed of the conductive member 10a. As shown in FIG. 2, the casing 10 includes a lower casing 11 and an upper casing 12 that are both made of metal (for example, aluminum). By fitting the lower housing 11 and the upper housing 12, the lower housing 11 and the upper housing 12 are electrically connected.

  The housing 10 stores a printed circuit board 13 on which a matching circuit, a battery storage unit, and the like which will be described later are mounted. A first power supply probe 13 a and a second power supply probe 13 b are mounted on the printed circuit board 13.

  As shown in FIG. 2, when the lower housing 10a and the upper housing 10b are fitted, the first feeding point 100a provided at the peripheral edge of the slit 14 on the inner surface side (lower side of the drawing) of the upper housing 10b and The first power supply probe 13a is electrically connected, and the second power supply point 100b provided at the peripheral edge of the slit 14 and the second power supply probe 13b are electrically connected.

  In the portable transmitter 1, the conductive member 10 a in which the slit 14 is formed is fed through first and second feeding points 100 a and 100 b provided on the peripheral edge of the slit 14, and the UHF band (for example, , 400 MHz band) function as a slit antenna for transmitting radio waves.

  FIG. 3 shows the configuration of the matching circuit 21 of the portable transmitter 1. The matching circuit 21 includes a capacitor 21a and a capacitor 21b. The capacitor 21a is connected in series with the conductive member 10a via the power supply probe 13a, and the capacitor 21b is connected in parallel with the conductive member 10a via the power supply probe 13b.

  Such a matching circuit 21 is connected to the conductive member 10a in which the slit 14 is formed, and the conductive member 10a is resonated to transmit radio waves.

  In such a configuration, when an operation button (not shown) is operated, the conductive member 10a is resonated by the matching circuit 21, and a radio wave for instructing locking control or unlocking control of the door of the vehicle 2 from the conductive member 10a. Is to be sent.

  Next, the positions of the first and second feeding points 100a and 100b will be described with reference to FIG. The slit antenna has a characteristic that current flows well at both ends in the longitudinal direction of the slit 14 and the current decreases at the center in the longitudinal direction of the slit 14. That is, the impedance is small near both ends of the slit 14 in the longitudinal direction, and the impedance is large at the central portion of the slit 14 in the longitudinal direction.

  In the slit antenna, first and second feeding points 100a and 100b are provided at positions facing each other across the rectangular slit 14. Further, in the slit antenna, there is an optimum feeding position at the peripheral portion of the slit 14. For example, when matching is performed at 50 ohms, the position at which the ohms are 50 ohms at the peripheral edge of the slit 14 is the optimum power feeding position.

  The wavelength of the 700 MHz band radio wave transmitted from the portable transmitter 1 is about 75 centimeters. However, the portable transmitter 1 is carried by the user, and the area of the conductive member 10a cannot be made sufficiently large, and the length Ls of the slit 14 cannot be made sufficiently long. For this reason, in this portable transmitter 1, efficiency is comparatively low and the impedance of the peripheral part of the slit 14 is large as a whole.

  Therefore, in the present portable transmitter 1, the first and second feeding points 100a and 100b are provided near the end of the slit 14 where the impedance is reduced and at a position where matching can be achieved.

  The length Ls of the slit 14 is such that the conductive member 10a is likely to resonate and maximize efficiency.

  FIG. 5 shows an example of frequency characteristics of the reflection coefficient S11 of a slit antenna in which the entire housing 10 is constituted by the conductive member 10a. By providing the first and second feeding points 100a and 100b at optimal positions, a slit antenna having a reflection coefficient S11 of about −38 dB in the 430 MHz band can be configured.

  According to the configuration described above, the housing (10) including the conductive member (10a) in which the slit (14) having the opening shape is formed, and the conductive member is provided in the first and the peripheral portions of the slit. Since power is supplied via the second feeding point (100a, 100b) and functions as an antenna for transmitting radio waves, the design can be improved while ensuring the transmission characteristics of the transmission radio waves.

  In addition, this invention is not limited to the said embodiment, Based on the meaning of this invention, it can implement with a various form.

  For example, in the above-described embodiment, an example in which the entire housing 10 is configured by the conductive member 10a has been described. However, a configuration in which the conductive member 10a is provided in a part of the housing 10 may be employed. For example, it is good also as a structure which provided the electroconductive member 10a in some housing | casing 10, such as the one end surface side of the longitudinal direction of the housing | casing 10. FIG.

  Moreover, as shown in FIG. 6, you may comprise so that the slit 14 may be provided in the end surface of the longitudinal direction of the housing | casing 10. As shown in FIG. When the user holds the portable transmitter 1 in his hand, if the user's hand touches the slit 14, the transmission characteristics may change. By providing 14, it is possible to make it difficult to touch the slit 14 when the user holds the portable transmitter 1, and it is possible to prevent the transmission characteristics from changing.

  Moreover, in the said embodiment, although the example provided with the housing | casing 10 shaped like a rectangular parallelepiped was shown, it is not limited to the housing | casing of the above shape.

DESCRIPTION OF SYMBOLS 1 Portable transmitter 10 Case 10a Conductive member 11 Lower case 12 Upper case 13a, 13b Feed probe 14 Slit 21 Matching circuit

Claims (4)

A portable transmitter that transmits radio waves for the control to the vehicle-mounted device (3) that controls the vehicle equipment mounted on the vehicle (2),
A housing (10) having a conductive member (10a) in which an opening-shaped slit (14) is formed;
The conductive member is fed through first and second feeding points (100a, 100b) provided on the peripheral edge of the slit, and functions as an antenna for transmitting the radio wave. Transmitter.   The portable transmitter according to claim 1, wherein the entire casing is configured by the conductive member.   The portable transmitter according to 1 or 2, wherein the conductive member is provided in a part of the casing.   The portable transmitter according to claim 1, wherein the slit is provided on one end surface of the casing in the longitudinal direction.

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