This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2007-130581, filed on May 16, 2007, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a wireless tag reader/writer antenna having an antenna which comprises electromagnetic-wave shields for shielding a wireless tag reader/writer from electromagnetic waves that are detrimental to the communication with wireless tags and which transmits and receives electromagnetic waves to and from wireless tags.
2. Description of the Related Art
During communication with wireless tags, electromagnetic waves may exist, which interfere with the electromagnetic waves being transmitted to, or received from, wireless tags, as will be explained with reference to the following example.
In regard to this, a technique of shielding wireless tags from electromagnetic waves detrimental to communication has been proposed (see, for example, Jpn. Pat. Appln. Laid-Open Publication No. 2005-266961). In the technique, a wireless tag reader/writer antenna is provided in a storing case that shields wireless tags from electromagnetic waves, and articles having wireless tags attached to them are stored in the storing case, whereby the wireless tags are shielded from electromagnetic waves.
Another technique of shielding a reader/writer from electromagnetic waves has been proposed (see, for example, Jpn. Pat. Appln. Laid-Open Publication No. 2005-175134). In this technique, a cover is attached to the antenna unit of a handy reader/writer in order to shield the reader/writer from electromagnetic waves and articles having a wireless tag each are inserted between the antenna unit and the cover. The reader/writer can thus be shielded from the electromagnetic waves detrimental to the communication.
Further, a technique of preventing the reflection of electromagnetic waves has been proposed (see, for example, Jpn. Pat. Appln. Laid-Open Publication No. 2000-137873). The technique is to bond a layer of material that absorbs electromagnetic waves to the inner surfaces of a metal case, thus preventing the reflection of electromagnetic waves at the metal parts.
Another technique of preventing the reflection of electromagnetic waves has been proposed (see, for example, Jpn. Pat. Appln. Laid-Open Publication No. 2002-64327). This technique is to bond a layer of material that absorbs electromagnetic waves to the walls and roofs of buildings, thus preventing the reflection of electromagnetic waves at the metal parts.
The techniques disclosed in Jpn. Pat. Appln. Laid-Open Publications Nos. 2005-266961 and 2005-175134 are disadvantageous, however. A number of articles having a wireless tag each must be taken out and inserted into the reader/writer, requiring much time and labor.
The technique disclosed in Jpn. Pat. Appln. Laid-Open Publications No. 2000-137873 is disadvantageous, too, because many layers of wave-absorbing material must be used to cover the inner surfaces of the metal case, inevitably raising the cost.
The technique disclosed in Jpn. Pat. Appln. Laid-Open Publication No. 2002-64327 is also disadvantageous in that the reflection of electromagnetic waves cannot be prevented within any metal case.
An object of the present invention is to provide a wireless tag reader/writer antenna that can efficiently shield a wireless tag reader/writer from electromagnetic waves that are detrimental to communication with wireless tags.
To achieve the object, a wireless tag reader/writer antenna according to an aspect of this invention includes: an antenna unit that incorporates a reader/writer antenna for transmitting and receiving electromagnetic waves to and from wireless tags; and a plurality of magnetic-wave shields that clamp the antenna unit and extend in a direction of radiating electromagnetic waves from the reader/writer antenna.
According to an aspect of the present invention, the wireless tag reader/writer can be efficiently shielded from electromagnetic waves detrimental to the communication with wireless tags by providing electromagnetic shields to the antenna unit. According to another aspect of this invention, an electromagnetic-wave shield can be detached and attached and can slide, enhancing the efficiency of handling articles that have a wireless tag each.
A wireless tag reader/writer antenna according to an embodiment of this invention will be described in detail, with reference to the accompanying drawings.
The present embodiment will be outlined.
The term “wireless tag” means a recording medium that can communicate by radio. Most wireless tags have an antenna and an IC chip, each. The wireless tag may further have a calculating function. Preferably, the wireless tag should have a portable size. Nonetheless, it may be much smaller. The wireless tag is known also as radio frequency identification (RFID).
The wireless tag 510 shown in
The wireless tag reader/writer 520 comprises an antenna unit 521, a reader/writer control unit 526, a modulating unit 522, a transmission amplifier 523, a reception amplifier 524, a demodulating unit 525, and an interface 530. The antenna unit 521 incorporates a reader/writer antenna 521a that transmits and receives signals to and from wireless tags in the form of electromagnetic waves. The reader/writer control unit 526 controls the communication with the wireless tag 510 and the hardware connected to it. The modulating unit 522 modulates the data supplied from the reader/writer control unit 526. The transmission amplifier 523 amplifies a modulated signal and transmits the same to the reader/writer antenna 521a. The reception amplifier 524 amplifies any modulated electromagnetic wave received. The demodulating unit 525 demodulates any modulated signal received. The interface 530 is connected to a high-order apparatus 603, such as a personal computer, and receives and transmits data from and to the higher-order apparatus. The reader/writer control unit 526 has a CPU 527, a ROM 528, and a RAM 529. The ROM 528 and RAM 529 store various data items.
The antenna unit 521 may be a handy wireless tag reader/writer that is provided in one housing, together with the wireless tag reader/writer 520.
<Configuration of Wireless Tag Reader/Writer Antenna of First Embodiment>
A first embodiment of the present invention will be described.
As shown in
<Configuration of the Electromagnetic-Wave Shields of First Embodiment>
Various configurations that the electromagnetic-wave shields 103 may have will be described below.
Each electromagnetic-wave shield 103 has an electromagnetic-wave absorbing layer on the side that contacts the antenna unit 102, and has an electromagnetic-wave reflecting metal layer on the side that faces away from the antenna unit 102.
The electromagnetic-wave reflecting metal layer is made of almost pure metal such as iron or copper or made of alloy such as stainless steel.
The electromagnetic-wave absorbing layer is made of, for example, synthetic resin, wood or cellulose. Alternatively, it may be made of any material that can efficiently absorb electromagnetic waves. The material capable of efficiently absorbing electromagnetic waves may be carbon-impregnated polyurethane, ferrite, or carbon-impregnated styrene foam. Nevertheless, the material is not limited to the ones exemplified here.
So configured, the electromagnetic-wave shields 103 can shield the wireless tag reader/writer from the electromagnetic waves coming from outside the wireless tag reader/writer antenna 101.
Each electromagnetic-wave shield 103 includes an electromagnetic-wave absorbing member. The electromagnetic-wave shield 103 may be composed of this electromagnetic-wave absorbing member only. Instead, it may have another electromagnetic-wave absorbing member on the inner side that contacts the antenna unit 102. This absorbing member is made of at least one of the wave-absorbing materials specified above.
As indicated above, the wireless tag reader/writer antenna 101 according to this embodiment includes a plurality of electromagnetic-wave shields 103. The shields 103 are secured to the antenna unit 102, clamping the antenna unit 102, and extend in the direction of radiating electromagnetic waves from the reader/writer antenna 104. Therefore, the shields 103 can efficiently block electromagnetic waves that are detrimental to the communication with wireless tags.
<Configuration of Wireless Tag Reader/Writer Antenna of Second Embodiment>
A second embodiment of the present invention will be described.
A rail-type attaching/detaching mechanism is shown in
In the wireless tag reader/writer antenna 201 according to the present embodiment, the electromagnetic-wave shields 203, which are secured to the antenna unit 202, may have different lengths as measured in the widthwise direction of the antenna unit 202. If this is the case, the number or thickness of articles that have wireless tags, with which the wireless tag reader/writer antenna 201 can communicate at a time, can be changed merely by selectively using the electromagnetic-wave shields 203 of different lengths.
The widthwise direction 205 of the antenna unit 202 is the distance by which the two electromagnetic-wave shields 204 clamping the antenna unit 202 are spaced apart from each other.
Another configuration that the wireless tag reader/writer antenna 201 according to the second embodiment may have will be described.
As
In the configuration of
The method of connecting the electromagnetic-wave shields 303 to the antenna unit 302 is not limited to the one explained with reference to
<Configuration of the Electromagnetic-Wave Shields of Second Embodiment>
The electromagnetic-wave shields of the second embodiment can have the configuration of the electromagnetic-wave shields of the first embodiment described above.
As described above, the wireless tag reader/writer antenna 201 according to this embodiment includes a plurality of electromagnetic-wave shields 203 which clamp the antenna unit 202, which can slide in the widthwise direction 205 of the antenna unit 202 and which extend in the direction of radiating electromagnetic waves from the reader/writer antenna 104. Hence, the electromagnetic-wave shields 203 can be detached if there are scarcely electromagnetic waves detrimental to the communication with the wireless tags. Thus, the number or thickness of articles that have wireless tags, with which the wireless tag reader/writer antenna 201 can communicate at a time, can be changed, if necessary, at high efficiency, only by replacing the electromagnetic-wave shields 203 with other shields.
<Configuration of Wireless tag Reader/Writer Antenna of Third Embodiment>
A third embodiment of the present invention will be described.
In
To render the electromagnetic-wave shield 804 detachable from the antenna unit 102, the attaching/detaching mechanism shown in
<Configuration of the Electromagnetic-Wave Shield of Third Embodiment>
The electromagnetic-wave shield of the third embodiment can have the configuration of the electromagnetic-wave shields of the first embodiment described above.
As described above, the wireless tag reader/writer antenna 801 according to this embodiment includes an electromagnetic-wave shield 803 which is shaped like a hollow cylinder having an open bottom, which is secured to the antenna unit 102, with the open bottom contacting the wave-radiating surface of the antenna unit 102, and which extends in the direction of radiating electromagnetic waves from the reader/writer antenna 104. Moreover, the shield 803 can be detachably secured to the antenna unit 102. The shield 803 can therefore efficiently block electromagnetic waves that are detrimental to the communication with wireless tags.
It should be noted that the present invention is not limited to the various embodiments described above. The components of any embodiment can be modified in various manners in reducing the invention to practice, without departing from the spirit or scope of the invention. Further, the components of the embodiments described above may be combined, if necessary, in appropriate ways, thereby to make different inventions. Still further, some of the components of any embodiment may not be used. Moreover, the components of the different embodiments may be combined in any desired fashion.
Number | Date | Country | Kind |
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2007-130581 | May 2007 | JP | national |