| The smart shelf is a typical application of the RFID,which is used to iden-tify goods on shelves,and will not misread into adjacent goods.The main chal-lenge for this application lies in the following aspects:(1)to ensure that the reading and writing area of the antenna are defined and limited near the shelf,and will not extend to other adjacent shelves;(2)the solution must be matched with the existing passive tag and reader in UHF band;(3)the structure of the reader antenna must be simple enough to mass production at low cost,and easy to change at the same time to adapt to different shelf sizes and types.Based on the background described above,this paper proposed a UHF band near-field reader antenna.The antenna is composed of a double-sided stripline,a double-sided balun,a air substrate layer and a finite ground plane.The end of the antenna has a impedance which is equal to the characteristic impedance of the double-side stripline.so travelling wave can spread along it.After matching optimization,the measurement bandwidth can covers the Chinese,European and American UHF standards(840MHZ to 840MHZ),read distance reached 7cm under the condition of S11≤-10dB.Then we added a little design in the end of the antenna,so that the reader can be used in Cascade to adapt to different ap-plication environment.After simulation and optimization,all the antennas can cover the UHF band,and the reading distance can reach 6cm under the condition of S11≤10dB.In addition,to reduce the cost of RFID system deployment in the practical application process,we present a polling system of reader antenna in this paper,which can be used after a reader to drive multiple reader antennas in TDMA mode.In this paper,the design process and the object of the polling equipment are given,and the testing process in the actual environment is presented.Finally,in order to solve the problem of channel congestion of railway wireless communication system,in this paper,we designed a antenna array car-rying orbital angular momentum which was based on GSM-R system.The an-tenna unit we used is patch antenna added a defected ground structure.And the antenna array is composed of eight antenna units placed in circular permutation.This paper introduces every detail during the design of the antenna unit and the array.Then the practical object picture and the test results are also given.The specific parameters of the antenna array are as follows:(1)the working band-width covers 885MHZ to 934MH;(2)the isolation between units is under-15dB;(3)communication channel number is greater than 3;(4)far field gain of the antenna array is greater than 6dB. |
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