The Design Of Controllable Interrogate Area UHF RFID Near-Field Reader Antenna

RFID(radio frequency identification)is a technology that using electromagnetic fields to automatically identify and track tags attached to objects.And RFID systems with non-contact high read and write speed attract more and more attention.However,in the conventional RFID applications,false positive issues about misreading may occur due to the high far-field radiation efficiency.Thus,in this research,near-field UHF RFID reader antennas have been introduced to maximize and confine fields within a controlled volume.The greatest design challenge for this kind of antenna is to produce a uniform field distribution in the near-field region and to attenuate field strength in the far-field region.In this paper,we try to define near-field controllable interrogated area and design RFID near-field reader antenna according to two kinds of mechanism.One mechanism is magnetic field coupling and another mechanism is electric field coupling.Firstly,a novel magnetic coupling reader antenna based on meander open-ended microstrip lines for UHF RFID near-field applications is proposed.Meander line units are introduced to generate a strong uniform magnetic-field distribution over a large interrogation with no null zones.The antenna can be adapted to appropriate scenarios conveniently in practical application by increasing or decreasing the number of the meander line units.And then,we improved above structure to propose a broadband magnetic coupling antenna with low far-field gain.Secondly,a novel multipolarized electric coupling reader antenna for UHF RFID near-field applications is proposed.The electric field excited by the antenna has multipolarization characteristics,and the field distribution is strong and uniform.And then,we proposed a topological structure of multipolarized RFID reader antenna for UHF near-field applications.Based on this structure,two antennas were designed and implemented by microstrip lines.By changing the number of units,which consists of an antenna,the interrogated area can be adjusted easily.All steps,such as analysis,simulation,processing and measurement,are shown to illustrate the good performance of the above antennas.This research solves some engineering problems and it is helpful for professional engineers.