Design And Research Of The Passive RFID Sensor Rectifying Antenna

The development of the Internet of things technology can not be a lack of the intelligent access terminal. Passive Radio frequency identification(RFID) tags for self sustained power supply not only can identify objects, but also can carry out sensing, computing and data communications autonomously. The power supply problem seriously restricts RFID tag to display its application potential. The power supply problem of the passive RFID tag is effectively solved by the technology of the rectenna(rectifying antenna) based on the wireless energy transmission.In this paper, the rectenna for passive RFID sensor working on 2.45 GHz was designed and studied by using circuit simulation software Agilent ADS and electromagnetic simulation software Ansoft HFSS. Rectenna design includes a receiving antenna and a rectifier circuit. Receiving antenna adopted the microstrip annular slot antenna with bi-directional radiation characteristics and broadband characteristics. Through slotting on the annular gap edge of antenna, introducing perturbation, realized circularly polarized radiation characteristics of the antenna. By opening aperture in the center of annular gap, achieved the purpose of suppression of harmonics and reducing antenna size. The maximum unilateral gain of receivin g antenna was 1.9d B. Antenna resonance bandwidths(VSWR <2) was 17.6% and the circular polarization bandwidth(AR <3d B) was 3.1%. The voltage-double rectifier circuit is used to increase the output voltage. Using a effective method of impedance matching, while using the matching structure of gradient microstrip line with broadband characteristics, the rectifier circuit had achieved good impedance matching with receiving antenna. At input power of 0d Bm, rectifier circuit can reach 35 % of the rectification efficiency and 0.5V of DC output voltage. At input power of 16 d Bm, the rectification efficiency can reach 58% and the DC output voltage can reach 4V. Finally, after the processing by photographic etching method,the rectenna was tested and analyzed.