JPH06268431A - Antenna for radio communication - Google Patents

Abstract

PURPOSE:To obtain an antenna for radio communication forming the communication area of the directivity of an asymmetric characteristic of the shape of a figure 8. CONSTITUTION:This device is equipped with at least one main loop antenna part 2 having the communication area of the directivity of the characteristic of the shape of a figure 8 with an aperture face 2A for transmitting and receiving an electromagnetic wave as a center. Also, the device is equipped with a slave loop antenna part 3 connected with the main loop antenna part 2, whose winding direction is different from that of the main loop antenna part 2, and the slave loop antenna part 3 is arranged in the neighborhood of the main loop antenna part 2 so that an aperture face 3A of the slave loop antenna part 3 can be opposed to the opening face 2A of the main loop antenna part 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication antenna used for communication using electromagnetic waves as a medium.

[0002]

2. Description of the Related Art An example of this wireless communication antenna is shown in FIG. This wireless communication antenna is composed of a loop antenna section 81, and is used by being connected to a transmission / reception device 82 for transmitting and receiving radio waves. As shown in FIG. 9, the loop antenna portion 81 has a directivity of an 8-shaped characteristic centered on the radio wave transmitting / receiving opening surface 81A of the loop antenna portion 81 and with respect to the vertical surface of the opening surface 81A. Has a communication area 83.

As shown in FIG. 10, some wireless communication antennas are provided with two loop antenna parts 91 and 92 which are connected to the transmitting / receiving device 93 and are installed horizontally. As shown in FIG. 11, the communication area by this wireless communication antenna is a communication area 83 shown in FIG.
The area 94 looks like a combination of the above, and a wider communication area can be secured as compared with the wireless communication antenna of FIG.

Such a radio communication antenna has a wide range of applications and is used in various devices.

[0005]

A radio communication antenna as shown in FIG. 8 may be used for gate management using a data carrier as shown in FIG. 12, for example. Here, especially the magnetic field component of the electromagnetic wave is utilized. In this case, the opening surface 81 of the loop antenna portion 81
The communication area 83, which is perpendicular to A, has a symmetrical 8-shaped configuration. Therefore, in addition to the person 111 who passes through the area portion 83A of the communication area 83, which is a detection target in the gate management, the person 112 who passes through the area portion 83B is also detected. For this reason, there is a possibility that an erroneous communication with the desired area portion 83A may occur, and therefore the area portion 83B must be a forbidden zone.

The wireless communication antenna shown in FIG. 10 also has the same problem because the communication area 94 (FIG. 11) has a symmetrical shape.

An object of the present invention is to eliminate the above drawbacks and to provide a radio communication antenna for forming a communication area with a directivity of an asymmetrical figure-eight characteristic.

[0008]

In order to achieve the object, the present invention has an opening surface for transmitting and receiving electromagnetic waves as a center,
In a wireless communication antenna including at least one main loop antenna section having a communication area based on the directivity of a figure eight characteristic, a slave loop antenna section connected to the main loop antenna section and having a winding direction different from that of the main loop antenna section. The sub-loop antenna section is arranged in the vicinity of the main loop antenna section so that the opening surface of the sub-loop antenna section faces the opening surface of the main loop antenna section.

[0009]

With this configuration, the communication area of the main loop antenna section is divided into one including the sub loop antenna section and one not including the sub loop antenna section. The slave loop antenna section has a winding direction different from that of the main loop antenna section. As a result, in the communication area including the slave loop antenna section, the transmission / reception level obtained from the main loop antenna section becomes lower than the transmission / reception level obtained in the communication area not including the slave loop antenna section.

[0010]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention. This wireless communication antenna is used by being connected to a transmitter / receiver 1 for transmitting and receiving electromagnetic waves, and includes a main loop antenna unit 2 and a slave loop antenna unit 3.

Since the main loop antenna section 2 is the same as the loop antenna section 81 shown in FIG. 8, its description will be omitted.

The slave loop antenna section 3 has a circular shape similar to that of the main loop antenna section 2, and has the same shape as in FIG.
It has a directivity with an 8-shaped characteristic. This slave loop antenna unit 3
The slave loop antenna section 3 is installed such that the opening surface 3A thereof is separated from the opening surface 2A of the main loop antenna section 2 by a predetermined distance and faces each other. The sub loop antenna section 3 is wound such that the sub loop antenna section 3 is wound in the opposite direction to the main loop antenna section 2. Further, the number of turns of the sub loop antenna unit 3 is smaller than that of the main loop antenna unit 2.

The slave loop antenna section 3 is connected in series to the main loop antenna section 2, as shown in FIG. At this time, the capacitor 4 is connected in series to the series circuit of the sub loop antenna unit 3 and the main loop antenna unit 2. The capacitor 4 resonates in series with the coiled main loop antenna unit 2 and the slave loop antenna unit 3,
Increase the efficiency of the antenna.

As a connection between the slave loop antenna section 3 and the main loop antenna section 2, there is one shown in FIG. 3 in addition to FIG. Here, the slave loop antenna unit 3 is connected in parallel to the main loop antenna unit 2. Further, a series resonance capacitor 4 is connected in series to the parallel circuit.

The operation of the embodiment having such a configuration will be described.

First, when electromagnetic waves are transmitted using the wireless communication antenna of this embodiment, the following is performed. The transmission signal from the transmitter / receiver 1 is applied to the main loop antenna unit 2 and the slave loop antenna unit 3 in phase.

At this time, the main loop antenna section 2 is shown in FIG.
Since it has the directivity of the figure 8 characteristic as shown in Fig. 9, the electromagnetic wave radiated from the main loop antenna unit 2 is in the same state as in Fig. 9. Further, the slave loop antenna unit 3 is also shown in FIG.
Although it has a directivity with an 8-shaped characteristic as shown in FIG. 3, the winding direction of the sub loop antenna unit 3 is opposite to the winding direction of the main loop antenna unit 2. As a result, the electromagnetic wave radiated from the slave loop antenna unit 3 is transmitted to the main loop antenna unit 2
It acts so as to cancel the electromagnetic waves emitted from. Further, since the number of turns of the sub loop antenna unit 3 is smaller than that of the main loop antenna unit 2, the electromagnetic wave emitted from the sub loop antenna unit 3 is weaker than that emitted from the main loop antenna unit 2.

As a result, the directivity of the radio communication antenna has an asymmetrical figure-eight characteristic, and the transmission area becomes an asymmetrical figure-eight area 5, as shown in FIG.

Next, when an electromagnetic wave is received by using the antenna for wireless communication of this embodiment, it is as follows. The directivity of the main loop antenna unit 2 and the slave loop antenna unit 3 when receiving an electromagnetic wave is the same as that when the electromagnetic wave is radiated, as shown in FIG. However, the slave loop antenna unit 3
Since the winding direction of is opposite to the winding direction of the main loop antenna unit 2, the phase of the received signal generated by the slave loop antenna unit 3 receiving the electromagnetic wave is opposite to the phase of the received signal of the main loop antenna unit 2. become. Furthermore, since the number of turns of the slave loop antenna unit 3 is smaller than that of the main loop antenna unit 2,
The received signal of the slave loop antenna unit 3 is weaker than the received signal of the main loop antenna unit 2.

As a result, the reception signal of the slave loop antenna section 3 and the reception signal of the main loop antenna section 2 cancel each other out, and the reception area is the asymmetrical 8-shaped area 5 as in FIG. become. That is, the area 5B including the slave loop antenna unit 3 is narrower than the area 5A not including the slave loop antenna unit 3.

As described above, according to this embodiment, it is possible to shape the communication area based on the directivity of the asymmetrical 8-shaped characteristic.

The radio communication antenna of this embodiment is applied to gate management using a data carrier as shown in FIG. 5, for example. Here, especially the magnetic field component of the electromagnetic wave is utilized.

In this application example, the number of turns of the main loop antenna unit 2 is 15 turns, and the number of turns of the sub loop antenna unit 3 is 6 turns. Further, when the transmitter / receiver 1 resonates with the capacitor 4, it is necessary to determine the distance between the main loop antenna unit 2 and the slave loop antenna unit 3, and the main loop antenna unit 2 and the slave loop antenna unit 3 are separated from each other. Distance 15
cm. In addition, the two wires are bundled so that the directions of the currents flowing in the connection wires from the loop antenna units 2 and 3 to the transmission / reception device 1 are opposite to each other, and the area formed by these wires is reduced so that the connection wires are connected. Make the generated magnetic field component negligible.

When the main loop antenna section 2 and the slave loop antenna section 3 are set in this way, on the person 101 side, the radio communication antenna transmits and receives received signals even if the person 101 is about 90 cm away from the main loop antenna section 2. Send to device 1. On the other hand, on the person 102 side, the main loop antenna units 2 to 50
When the distance is about cm (35 cm from the slave loop antenna unit 3), the wireless communication antenna stops transmitting the reception signal.

As a result, the person 1 who has not passed through the gate
False access to 02 is reduced. As a result,
The forbidden band can be made narrower than before, and the layout area can be made small, especially when a plurality of gates are installed.

Although the capacitor 4 for series resonance is used in this embodiment, the capacitor 4 may be omitted. Further, at the time of reception, the capacitor 4 may be switched and used for parallel resonance.

In this embodiment, the number of turns is reduced to adjust the sensitivity of the slave loop antenna section 3. However, the number of turns is not limited to this.
The area may be reduced.

The transmitting / receiving apparatus 1 is attached to this embodiment, but the present invention is not limited to this, and the radio communication antenna of this embodiment may be attached to the transmitting apparatus or the receiving apparatus for use. .

Further, in this embodiment, the main loop antenna portion 2 and the sub loop antenna portion 3 are formed in a circular shape, but the shape is not limited to this and may be a square shape. Further, as shown in FIG. 6, two sets of the rectangular main loop antenna unit 11 and the quadrangular loop antenna unit 12 are connected to the transmitter / receiver 13, and these two sets of antennas are arranged in the horizontal direction. May be. As a result, the communication area is expanded. Further, as shown in FIG. 7, two sets of antennas including the main loop antenna unit 11 and the slave loop antenna unit 12 may be arranged in the vertical direction.

[0031]

As described above, according to the present invention, in the communication area including the slave loop antenna section, the transmission / reception level obtained from the main loop antenna section is obtained in the communication area not including the slave loop antenna section. It will be lower than the level. As a result, the present invention can change the directivity from the conventional symmetrical 8-shaped characteristic to the asymmetrical characteristic.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing a connection between a main loop antenna unit and a slave loop antenna unit.

FIG. 3 is a diagram showing a connection between a main loop antenna unit and a slave loop antenna unit.

FIG. 4 is a diagram showing a communication area of the embodiment of FIG.

FIG. 5 is a diagram showing a state in which the embodiment of FIG. 1 is applied to gate management.

FIG. 6 is a diagram showing an arrangement of two sets of antennas.

FIG. 7 is a diagram showing an arrangement of two sets of antennas.

FIG. 8 is a diagram showing an example of a conventional wireless communication antenna.

9 is a diagram showing a communication area of the antenna of FIG.

FIG. 10 is a diagram showing another example of a conventional wireless communication antenna.

11 is a diagram showing a communication area of the antenna of FIG.

FIG. 12 is a diagram showing an application example of a conventional wireless communication antenna.

[Explanation of symbols]

 2 Main loop antenna part 2A opening face 3 Secondary loop antenna part 3A opening face

Claims (1)

[Claims] 1. A center of an opening for transmitting and receiving electromagnetic waves,
A wireless communication antenna comprising at least one main loop antenna section having a communication area based on the directivity of a figure 8 characteristic, the sub loop being connected to the main loop antenna section and having a winding direction different from that of the main loop antenna section. A wireless communication comprising an antenna section, wherein the slave loop antenna section is arranged in the vicinity of the main loop antenna section so that the opening surface of the slave loop antenna section faces the opening surface of the main loop antenna section. For antenna.