| The Radio Frequency Identification technology (RFID) has been rapidlydeveloped and widely used in recent years. RFID tag antenna is a crucial part of RFIDsystem, which acts as a media for the electromagnetic power transmission. Theperformance of tag antenna greatly impacts the whole RFID system. Therefore, theresearch of RFID tag antenna has been paid more and more attention in recent years.At the same time, along with the GPS bands of L1(1.57542GHz), L2(1.2276GHz)and L5(1.17645GHz) were opened gradually, and Chinese Compass NavigationSatellite System (CNSS), or “BeiDou” in its Chinese name, is continuously mature, itis very important to carry out the research broadband circularly polarized antennasfor CNSS applications.Firstly, a novel RFID tag antenna with a coupled loop added on a meandereddipole is proposed to match the complex impedances of chips without additionalmatching network for both915MHz and2.45GHz RFID systems. The antenna has alow-profile, compact size (15mm x75mm), and its maximum gain is over2dBi inH-plane on both bands. An equivalent circuit of the antenna is analyzed and thedesign procedure is presented.Secondly, a mismatching design method for RFID tag antenna application hasbeen presented. Through the analysis of the Radar Cross Section (RCS) in RFIDsystem, this design method can achieve the largest delta RCS than traditional way sothat it optimizes the stability of the RFID system.Thirdly, a novel compact QHA attached a novel low-profile feed network on itsbottom end is proposed to achieve broadband CP radiations. Its principle of thewideband characteristics and details of the design are discussed. Based on this study,assembled broadband quadrifilar helix antennas for CNSS have been proposed, whichcould achieve duplex communication of CNSS system. |
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