| RFID (Radio Frequency Identification) is a kind of technology which canidentify target automatically and access to information by using RF signal. In the"Development plan during the twelfth five-year for internet of things" releasedby MIIT, it accentuated the development of the RFID core technology and itsapplication in the logistics industry, which greatly promoted the rapiddevelopment of China's RFID industry.With the development of reform for the hospital logistics management, italways has some issues for the laundry business of medical linen (Generic termfor sheets, duvet cover and pillowcases) and uniform. For instance, it has therisk of cross infection and it takes long time (An average of100pcs inventory byevery5minutes) to count the quantities of dirty medical linen and uniform bymanual during the transfer process; the medical linen and uniform whichbelongs to various departments of the hospital used by other departments, which lead to the washing costs disputes; it cannot count out the wash times accuratelyof the medical linen and uniform that belongs to high-polluted departments, as aresult, it's in the lack of timely retirement and replacement.It can solve the issues above by identifying the clothes with RFID tagswhich have been written the clothes information in it. But the package of clothesused by domestic hospitals (can be equivalent to a cylinder with the diameter of0.6-0.8m and the height of0.6m) cannot go through the RFID tunnel with acaliber of0.5×0.5m commonly used on the market at home and abroad. In thispaper, we realized two kinds of RFID tunnels which working on HF13.56MHzand UHF920MHz with a caliber of1×1m for clothes-counting by the successfulapplication of the multi-antenna elements. It filled the gap in the market for suchlarge-caliber RFID tunnel.When the RFID system works on the frequency range of HF, its workprinciple is inductively coupled. For the HF RFID tag with the diameter of15mm and the thickness of2mm, traditional work mode of inductively coupledcannot meet the read range for more than0.5m. So the electromagneticsimulation model of a1×1m-caliber RFID tunnel with3-antenna elements hasbeen established. It simulated that when a RFID tag goes through the RFIDtunnel, it can get the voltage more than6.2V, which can support the NXPI-CODE1chip's working. And the3-antenna elements can get the return loss about-20dB when they work together. Based on the feasibility of theelectromagnetic simulation results, we manufactured the HF RFID tunnel, whichinternal dimension is1×1×3m. The testing results improved that the RFIDtunnel has the ability to get the information of30clothes with RFID tagsaccurately in8-10s by getting the data together and eliminating the duplicationof data.When the RFID system works on the frequency range of UHF, its workprinciple is electromagnetic radiation. According to the specification of UHFRFID tag which is manufactured by Fujitsu, its read range is1.16m when theRFID reader's antenna has the transmit power of2W. We used the design of3-antenna elements to ensure that the electromagnetic radiation area completelycovered the interior of the tunnel when the internal dimension of UHF RFIDtunnel is1×1×1m. The testing results improved that the RFID tunnel has theability to get the information of100clothes with RFID tags accurately in3-5sby getting the data together and eliminating the duplication of data. The designsuccessfully achieved the miniaturization of the equipment and the high speed ofthe detection process, as well as the scale of the detected objects.As mentioned above, two kinds of RFID tunnels with a caliber of1×1m forclothes-counting have been developed successfully in this paper based on thedesign of multi-antenna elements, and it solved the common issues of single antenna in large-caliber RFID tunnel as the following: the limit of work range, asingle electromagnetic coupling direction or polarization direction, the shieldingeffect between the RFID tags on surface and the other RFID tags when RFIDtags stacked densely.UHF RFID tunnel designed in this paper has been successfully applied tothe domestic hospital and laundry industry, which can count the quantities forthe different kinds of clothes, especially for the high-polluted items contactlessly,rapidly and accurately. And it has occupied more than80%of the total numberof RFID tunnels for clothes-counting used in domestic laundry market so far. |
