Research And Design Of UHF RFID Near-Field Reader Antenna For Complex Applications

With the continuous progress of Informatization China,Internet of Things technology has become a hot spot on future development.RFID(Radio Frequency Identification)is a key technology in the field of Internet of Things technology,while RFID reader antenna directly determines the recognition range,detection distance and other performance of RFID systems.This paper mainly focuses on the near-field UHF RFID reader antenna in complex scenarios,the main research content and innovation points are as follows:A monopole electrically large single-loop near-field reader antenna based on staggered coupling structure is proposed.Four monopole structures are connected by "sequential rotation" and "staggered coupling",forming a single-loop near-field reader antenna.Increase the 100%recognition space of the large single-loop reader antenna to 240 mm ×240 mm × 40 mm.A parallel two-line near-field reader antenna based on the X phase-shifter structure is proposed.Through a set of parallel two-line structure,an enhanced near-field magnetic field is formed between the parallel two lines,and the X phase-shifter structure is combined to achieve a rapid transition at the minimum current point position,effectively reducing the near-field magnetic field void and ensuring the uniform distribution of the near-field magnetic field.Antennas can be flexibly refactored for different recognition sizes:1×8 expansion,2×5 expansion,3×3 expansion to 65 cm×10 cm,42 cm×12 cm,27 cm×15 cm,respectively.Three near-field reader antennas with low gain are proposed.Aiming at the industry problem with high misreading rate and high missed reading rate of RFID recognition system in "semi-open" metal shelf environment,based on the structure of "open-end microstrip transmission line resonator",the radiation near-field low gain linearly polarization and circular polarization array elements are designed,combined with the near-field phased focusing principle,the near-field electric field generated by the antenna is focused,which avoids the antenna misreading the tags outside the identification area,and ensures a uniform electric field coverage in the recognition area.The antenna recognition area is expanded by the way of antenna unit polling.The experimental results show that:in the 1 m × 0.8 m × 0.96 m size "semi-open" metal shelf environment,excluding the nodal position due to metal shelf reflections,the rest of the locations achieve 100%reading rate.And beyond the identification area,misreading is completely suppressed.