| RFID (Radio frequency Identification) is a newly invented automatic identification technology. The interrogator makes use of electromagnetic wave to communicate with tag, which has features of non-touch, fast identification, recycle of tags make RFID vast available and great commercial potential.Firstly, the far field features of normal antenna and RFID's antenna were analyzed based on the theories of antenna's radiation, reception, scattering. The power transmission and the method of modulation used in RFID system technologies were also analyzed. The RCS (Radar Cross Section) was proved as one of the key factors on the performance of the RFID's tag. Two types of tags were simulated with HFSS simulation software, the calculated RCS of two types of tags validates the theories discussed before.Two methods of 860-960MHz tag's performance test, which are Circulatorseparating signals method and Transmission and receiving antennas method, were researched. Thus two types of RFID performance test systems based on two methods respectively were set up with Circulator, Signal generator, Real time spectrum analyzer, High power amplifier, Antennas. The RFID performance test system has the ability to conduct tests including Writing/Reading minimum electric field intensity, Sensitivity of tags, Maximum working field intensity, Anti-jamming ability and so on. And two types of tags were tested on the system described before. The data of tests show the reliability and availability of RFID performance test system.Two helical antennas were designed and made for the use of RFID performance test system set up with the method of transmission and receiving antennas. The basic parameters of two antennas were calculated by experienced equations. The accurate parameters such as Antenna gain and Directivity pattern were attained with HFSS software's simulations. The parameters of VSWR and Isolation between two antennas measured with Vector Network Analyzer (HP 8720D) are in good agreement with the calculations before. |
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