| RFID (Radio Frequency Identification) as a key technology for the Internet of Things Applications, has been widely used in many industries. The tag antenna is an important part of the RFID system. Miniaturezation, broadband, multi-band is the direction of development. Microstrip antenna is widely used in RFID system for its simple structure, easy processing, low cost.The main work of this paper is the research about the miniaturization and dual of the patch antenna. It is can increase the applications of the antenna and control antenna’s costs by reducing the size of the antenna. The miniaturization of the antenna has been a research focus. RFID band is no uniform standard in the world which is the biggest problem with RFID. Study dual-band or multi-frequency antenna become necessary. It can make one RFID tag to be applied to multiple systems.Firstly, the radiation mechanism and analysis method of the microchip antenna is introduced in this paper. Using the transmission line equivalent method, formulas are deduced to calculate the size of the rectangular patch antenna and dipole patch antenna. Then we simulate the two patch antenna by ADS (Advanced Design System) simulation software. The simulation results are concordant with the theoretical calculations. Last, two miniaturized patch antennas are designed. One is a small printed antenna work at2.45GHz. After emulator the antenna by ADS software, simulation results show that it can covering frequency ranges of2.345-2.636GHz when return loss is less than-10dB. The other is a miniaturized dual-band printed antenna at2.4GHz and5.7GHz.Simulation results show that it can covering frequency ranges of2.348-2.625GHz and5.367-6.475GHz when return loss is less than-15dB. The measurement results are in great agreement with the simulation results, which showed that the two antennas can absolutely fit the use of RFID. It’s prove the design and simulation software are accurate and reliable.The innovative points in this paper can be summarized as follows:1. The miniaturization was achieved by jagged edge. The jagged edges can increase the current path to reduce the size of the antenna.2. Simulation results show that the miniaturized antenna’s performance was deteriorated. The main reason is current path will appear around the corner in jagged edges, which causes the EMI(Electromagnetic Interference).To solve this problem, we further use the arc edge instead of the jagged edges to optimize. The simulation results show that the antenna performance has been greatly improved after the use of arcs instead of serrated.3. Through adding metal wire and loading slot, the miniaturization and dual-band were achieved. Gap loading is a common method of achieving antenna dual-band work. Adding metal wire can increase the current path to reduce the size of the antenna. This paper placed the metal wire in the gap. So the antenna structure is more compact.4. To improve the performance of the antenna, the oval type slot was used in this paper. Compared with the rectangular gap, oval gap reduces the mutation of the current path. A comparative study of the antenna before and after the optimization was taken by using ADS simulation software. The results show that the antenna have improved in terms of bandwidth, return loss, impedance matching, etc.. |
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