JP2010068275A - Transmission antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an efficient transmission antenna capable of high-speed transmission without a damping resistor. <P>SOLUTION: This invention relates to a transmission antenna having such a structure that a coil is wound around a core. In the transmission antenna, a coil 3 is wound around a core consisting of a magnetic material 2 and a conductor 1 which are overlaid on each other. In the core, the conductor is sandwiched between two magnetic substances 2a and 2b, and the core is wound with the coil 3. The magnetic substance 2, the conductor 1, and a substrate 4 are stacked on each other. The coil 3 is wound around the core having the structure. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transmission antenna used for a keyless entry used in a vehicle or a house entrance door.

As a keyless entry for a vehicle, etc., a device is generally used in which the vehicle-mounted unit locks or unlocks the door by transmitting and receiving digital data of encrypted vehicle information via radio waves when the user operates a button on the remote unit. It is.
Such a device is an LF band (low frequency 30 to 300 KHz) short-range communication system, and the transmitting antenna of the in-vehicle unit is mounted on a handle of a door knob or the like. As a modulation method, amplitude displacement modulation (ASK modulation) is often used.

  A conventional transmitting antenna is composed of a bobbin, a coil, and a core such as ferrite. The coil is wound around the outer periphery of the bobbin, and the core is inserted into the through hole of the bobbin.

FIG. 6 is an example of a circuit diagram of a conventional antenna device, and FIG. 7 is an example of operation waveforms of the circuit of FIG.
6, the transmission unit 50 includes a logic circuit 54 comprised of the NAND circuit, a transistor _{Q 1} made of p-type in the power MOSFET, the transistor _{Q 2} to which an n-type power MOSFET. Connect the source of the transistor _{Q 1} to the power supply voltage _{V DD,} its source connected to the transistor _{Q 2} to ground GND, and connected to the drain of the transistors _{Q 1} and _{Q 2} together. Terminal 52 and the terminal 53 are input to the logic circuit 54, the output signal 55 of the logic circuit 54 is input to the gate of the transistor _{Q 1, Q 2.}
Antenna 51 resistance R, coil L, consist capacitor C, between the common connection point and the ground GND of the drain of the transistor Q _1, the transistor Q _2, the damping resistor R and a coil L and a capacitor C are connected in series .
Transmitting data to the input terminal 52 of the logic circuit 54, the carrier wave is input to the input terminal 53, the modulation signal to the output terminal 55 is input to the gate of the transistor Q _1, Q _2.
In FIG. 7, a waveform a is transmission data at the terminal 52, a waveform b is a carrier wave at the terminal 53, and a waveform c is a voltage V _AB between the terminals AB.
JP 2008-148279 A Japanese Patent No. 2005-175964

FIG. 8 is an example of an operation waveform when there is no damping resistor R in FIG. A waveform a is transmission data, a waveform b is a carrier wave, and a waveform c is a voltage V _AB between terminals AB.
As shown in the figure, when there is no damping resistor R, the waveform of the rising edge e ₁ and the falling edge e ₂ of the voltage V _AB is greatly increased. In such a system, in order to perform high-speed communication, the voltage V _AB between the terminals AB must be switched on and off at high speed. Therefore, the rise time and fall time must be steep.

In general, the rise time and the fall time are substantially proportional to the Q value of the antenna. Therefore, in the conventional transmission antenna, the antenna band is widened by suppressing the Q value of the antenna by using the damping resistor R. In addition to improving the broadness, the rise time e ₁ and the fall time e ₂ were steep.

However, the use of a damping resistor has a problem of reducing power efficiency because it consumes energy.
In addition, since a large current flows in the damping resistor used for damping, a resistor having a large allowable power is required, and the shape becomes large. Alternatively, when a plurality of small resistors are used in parallel, a mounting area is required.
An object of the present invention is to provide an efficient transmitting antenna capable of high-speed communication without a damping resistor.

The transmitting antenna of the present invention is characterized in that, in a transmitting antenna in which a coil is wound around a core, the coil is wound around a core in which a magnetic material and a conductor are overlapped.
Further, the present invention is characterized in that a coil is wound around a core having a conductor sandwiched between two magnetic bodies. Furthermore, the present invention is characterized in that a coil is wound around a core in which a magnetic body, a conductor, and a substrate are overlapped.

  According to the present invention having the above-described configuration, the antenna Q can be suppressed without using a damping resistor by winding the magnetic material and the conductor on the overlapped core, so that efficient transmission capable of high-speed communication is possible. An antenna can be obtained.

  Embodiments of a transmitting antenna according to the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a perspective view of a transmitting antenna 10 according to a first embodiment of the present invention. In this transmitting antenna 10, a coil 3 is wound by using an insulated wire whose surface is insulated and coated on a core made of a thin magnetic material having the same shape as the magnetic body 2 and a magnetic body 2 made of a flat magnetic material having a square cross section. It is a turn. Here, the conductor 1 uses a metal foil or a copper plate, and in consideration of insulation from the coil, it is necessary to cover the conductor surface with an insulating coat or the entire circumference of the core with an insulating tape. The magnetic material may be a ferrite and amorphous magnetic material or a magnetic powder that is pressure-bonded.

(Second embodiment)
FIG. 2 shows a perspective view of a transmitting antenna 20 according to a second embodiment of the present invention. This transmission antenna 20 is obtained by winding a coil 3 using an insulated wire around a core sandwiching a conductor 1 using magnetic bodies 2a and 2b obtained by further thinning the magnetic body used in the first embodiment. is there. In the second embodiment, it is easy to ensure insulation between the winding 3 and the conductor 1 by forming the conductor 1 in a shape hidden by the magnetic bodies 2a and 2b. Also, the magnetic bodies 2a and 2b can be made thinner than the first embodiment, and flexibility is easily obtained.

(Third embodiment)
FIG. 3 is a perspective view of a transmitting antenna 30 according to a third embodiment of the present invention. FIG. 4 is a front view of the substrate of FIG.
This transmitting antenna 30 is obtained by winding a coil 3 around a core obtained by superposing a core magnetic body 2 used in the first embodiment and a conductor 1 on a substrate 4.

  As shown in FIG. 4, the substrate 4 uses a generally formed copper foil pattern as the conductor 1, and the shape thereof is the same as that of the magnetic body 2. And the some convex part 7 is provided in the opposing side surface parallel to the longitudinal direction of the board | substrate 4, and the coil 3 is wound around the convex part 7-7 using the insulated wire. As shown in the embodiment of the figure, the coil 3 is a three-divided coil. Compared with a coil that is not divided, the leakage of magnetic flux in the divided part mitigates an increase in self-inductance and further suppresses the Q value.

The substrate 4 includes portions (4a, 4b) extending in the longitudinal direction.
One extending portion 4a includes notches 8a and 8b for drawing out terminals of the coil 3 on both side surfaces, and patterns 9a and 9b for electrically connecting the terminals on the surface of the substrate. The other extending portion 4b is provided with notches 8c and 8d and patterns 9d and 9c in the same manner as the one extending portion 4a. Further, the extending portion 4c of the substrate has an electron for constituting an antenna. It has components and wiring patterns.

  According to the above embodiment, a general copper foil pattern formed on the substrate can be used as a conductor, and insulation from the coil can be easily formed by a resist or the like. Further, by providing the connection pattern, the connection to the external mounting board is facilitated. Further, since the coil 3 is wound between the projections divided by the plurality of projections 7, there is no need for a bobbin, the leakage of magnetic flux from the divided coil increases, and the increase in self-inductance is mitigated. Thus, the Q value can be suppressed. Furthermore, since the winding position of the coil 3 can be constrained by the convex portion 7, the winding position is difficult to shift and the variation in characteristics can be reduced. In addition, a recessed part may be provided instead of a convex part, and a coil may be comprised in several recessed part.

(Fourth embodiment)
Further, in FIG. 5, as in the second embodiment of FIG. 2, the insulated magnetic wires 2 a and 2 b are used to connect the insulated wire to the core sandwiching the substrate 4 of FIG. 4 used in the third embodiment. The coil 3 is wound using The fourth embodiment is the same as the contents described in the second and third embodiments, and the details are omitted.
In the first to fourth embodiments, a predetermined damping resistance can be obtained by changing the thickness of the conductor. In this embodiment, a conductor thickness of 30 μm was used. The inventors have studied that the copper foil thickness is 5 μm to 100 μm, and the transmission antenna Q is 35 or less.

  As described above, the transmitting antenna according to the present invention winds a coil around a core in which a magnetic body and a conductor are overlapped, thereby increasing the AC resistance in the coil due to the proximity effect between the magnetic body and the conductor, thereby increasing the Q value. A transmission antenna that can be suppressed and does not require a damping resistor is obtained. In addition, by using the substrate, it is possible to easily create and mount the transmission antenna by using the divided winding of the coil and the substrate pattern as conductors.

The transmitting antenna according to the present invention is not limited to the above embodiment, and can be variously modified within the scope of the gist thereof.
In particular, the magnetic body and the conductor may be a laminate of a plurality of thin flat plates. Further, a plurality of stacked layers may be used. Further, the copper foil pattern may be either the front or back surface or both surfaces, or may be an inner layer of the substrate. Further, the front and back patterns may be connected by through holes.

It is a perspective view which shows the 1st Example of this invention. It is a perspective view which shows the 2nd Example of this invention. It is a perspective view which shows the 3rd Example of this invention. It is a front view of the board | substrate in the 3rd Example of this invention. It is a perspective view which shows the 4th Example of this invention. It is a circuit diagram of a transmitting antenna and a drive circuit. It is a figure which shows the example of the waveform of the conventional transmission antenna. It is a figure which shows the example of a waveform when there is no damping resistance in the conventional transmission antenna.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductor 2 Magnetic body 3 Coil 4 Board | substrate 4a, 4b, 4c Board | substrate extension part 7 Protrusion part 8a-8d Notch part 9a-9d Pattern 10, 20, 30, 40 Transmitting antenna 50 Drive part 51 Antenna part 52, 53 Input terminal 54 logic circuit 55 output terminal Q1 p-type power MOSFET
Q2 n-type power MOSFET
R Damping resistor L Coil C Capacitor V _DD Power supply voltage GND Ground

Claims (6)

In the transmission antenna with the coil wound around the core,
The transmission antenna according to claim 1, wherein the core is formed by superimposing a magnetic body and a conductor. In the transmission antenna with the coil wound around the core,
The transmission antenna according to claim 1, wherein the core is formed by sandwiching a conductor between two magnetic bodies. In the transmission antenna with the coil wound around the core,
The transmission antenna according to claim 1, wherein the core is formed by superimposing a magnetic body, a conductor, and a substrate.   3. The transmitting antenna according to claim 2, wherein the substrate is provided with a plurality of convex portions or concave portions on side surfaces facing in the longitudinal direction, and a winding portion of the coil is provided between the convex portions or between the concave portions.   5. The transmitting antenna according to claim 3, wherein the conductor is a conductor pattern provided on a substrate.   6. The transmitting antenna according to claim 1, wherein the magnetic body and the conductor are formed by laminating at least one thin flat plate layer.

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