Experimental Design of an Active Antenna for Radio Frequency Identification Applications

Abstract

Radio frequency identification (RFID) is the process of acquiring information by use of electromagnetic energy. These systems are completely noncontact and often utilize microwave components. The need for smaller components, less cost, and lower power consumption make the active antenna well suited for this application. This study attempts to develop a planar, FET based integrated active antenna for RFID applications. First a passive microstrip ring antenna is developed for integration with a nominal 50 ohm output oscillator. The antenna exhibits a 70 degree beamwidth in the E-plane with a -18 dB down cross-pol and an 80 degree beamwidth in the H-plane with a -30 dB down cross-pol. The return loss is -28.5 dB into 50 ohms. Second, a 5.8 GHz oscillator design is explored using S-parameter techniques and CAD simulations. Although the initial design does not meet specifications for integration with the microstrip ring antenna, the experimental results later verify the accuracy of the CAD simulations. This study concludes with an analysis of active antenna measurements based on the continued research to develop the oscillator for integration with the microstrip ring antenna.