JPS62123383A - Tag detector - Google Patents

Abstract

PURPOSE:To make it possible to adjust the detection range of a tag, by changing the antenna characteristics such as the directional pattern, and antenna gain of a characteristic variable antenna. CONSTITUTION:A tag detection apparatus A contains a horn antenna 3 and a receiving apparatus 4 and the antenna 3 is capable of adjusting the size of the aperture surface thereof and, therefore,the gain or directional pattern of the antenna 3 can be adjusted. The apparatus 3 detects the radio wave received by the antenna 3 to detect the presence of a tag 2. A moving body 1 is present in front of the antenna 3 and is transferred, for example, to a direction vertical to that of the apparatus A on a conveyer and the tag 2 is mounted to the surface of the moving body 1 in the side opposed to the apparatus A. This tag 2 oscillates a radio wave by the oscillator mounted therein or reflects the radio wave emitted from the apparatus A to emit the radio wave. By this method, the detection range of the tag can be adjusted.

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a tag detection device that detects the presence of a tag by receiving radio waves from a tag attached to a moving object, and the detection range can be adjusted depending on the installation location. It is particularly suitable for applications where adjustment is required.

(Background technology) FIGS. 5 and 6 are explanatory diagrams of conventional tag detection devices, respectively. The tag detection device Δ shown in FIG. Tag 2 is detected by detecting the wave at. Further, the tag detection device A shown in FIG. 6 detects the tag 2 by receiving radio waves transmitted from the tag 2 using the antenna 3 and the receiving device i4.

However, in such a conventional tag detection device, since the gain and directivity pattern of the antenna 3 are constant, detection [Jtl fine adjustment and detection When setting the detection range according to the target, it was necessary to replace the antenna with one with different characteristics or change the mounting location of the antenna.

(Object of the invention) The present invention was made to solve the above-mentioned problems, and its purpose is to arbitrarily increase the detection range without replacing the antenna or changing the mounting location. An object of the present invention is to provide a tag detection device that can be adjusted.

(Disclosure of the Invention) As shown in FIG. 1, the tag detection device according to the present invention has an antenna 3 that receives radio waves from a tag 2 attached to a moving object 1. In a tag detection device A that detects the presence of a tag 2 based on a signal, an antenna 3 that receives radio waves from the tag 2 is a variable characteristic antenna whose detection range can be adjusted.

Therefore, in the present invention, the detection range can be adjusted by changing the antenna characteristics such as the directivity pattern and antenna gain of the antenna 3, and the detection range can be adjusted by changing the antenna or changing the mounting position as in the conventional method. Even without doing this, the detection range can be finely adjusted to prevent false detection due to externally radiated radio waves, and the detection range can be set according to the detection target.

Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. FIG. 1 is a perspective view showing the appearance of a tag detection device according to an embodiment of the present invention. In the figure, tag detection device A includes a horn antenna 3 and a receiving device 4. The horn 7 antenna 3 can be adjusted in its opening size, thereby making it possible to adjust the gain and directivity pattern of the antenna. The receiving device 4 detects the presence of the tag 2 by detecting the radio waves (microwaves in this case) received by the horn antenna 3 . There is a moving object 1 at the end of the horn antenna 3, and this moving object 1
is transported, for example, on a conveyor in a direction perpendicular to the direction of the tag detection device A, and the tag 2 is attached to the surface facing the tag detection device A. The tag 2 emits radio waves by oscillating radio waves using a built-in oscillator or by reflecting radio waves emitted from the tag detection device.

FIG. 2 is a characteristic diagram showing the directivity pattern of the horn antenna 3. In the figure, in front of the horn antenna 3,
Left, rear, and right are 0°, 90°, and 180°, respectively.
The directivity pattern of the antenna 3 is shown by a curve representing the antenna gain in each direction in polar coordinates. The directivity pattern shown by the solid line in the tjS2 diagram has sharp directivity, and has a large gain in the ()° direction, but the gain rapidly decreases as it deviates from the 0° direction. It has become a characteristic. This directivity pattern is particularly effective when the distance between the tag 2 and the tag detection device is relatively long, as shown in the usage example in Figure f53, for example.

The directivity pattern shown by the broken line in FIG. 2 has somewhat broad directivity, and has approximately the same gain over a relatively wide angular range from +45° to -45°. This directivity pattern is particularly effective when the distance between the tag 2 and the tag detection device A is relatively short, for example as shown in the usage example of FIG.

The horn antenna 3 has a movable upper horn 31 and a lower horn 32, and a fixed horn base 33. By screwing the screw 34, the upper horn 31
And the lower horn 32 can be moved up and down relative to the horn base 33. When the relative distance between the upper horn 31 and the lower horn 32 becomes longer, the aperture area of the horn becomes larger, and when the distance becomes shorter, the aperture area of the horn becomes smaller, so the aperture area of the antenna 3 is adjusted. This allows the directivity pattern of the antenna 3 to be changed as shown in the characteristic diagram of FIG.

(Effects of the Invention) According to the present invention, the detection range of the tag can be adjusted by changing the antenna characteristics such as the directivity pattern and antenna gain of the variable characteristic antenna. The effect is that the detection range can be fine-tuned to prevent false detections caused by externally radiated radio waves, and the detection range can be set according to the detection target without having to change the mounting position or the like. There is.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing the external appearance of a tag detection device according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the directivity pattern of the horn antenna used in the above embodiment, and Fig. f53 and fjS4 are the same as above. FIGS. 5 and 6 are explanatory diagrams showing the usage conditions of the embodiment, respectively, and FIGS. 5 and 6 are explanatory diagrams showing the usage conditions of different conventional examples. 1 is a mobile object, 2 is a tag, 3 is an antenna, and A is a tag detection device.

Claims (2)

[Claims] (1) In a tag detection device that has an antenna that receives radio waves from a tag attached to a moving object and detects the presence of the tag based on a signal received by this antenna, the antenna that receives the radio waves from the tag detects the presence of the tag. A tag detection device characterized by having a variable characteristic antenna whose range can be adjusted. (2) The tag detection device according to claim 1, wherein the variable characteristic antenna is a horn antenna whose aperture size can be adjusted.