Publication

Abstract : Planar RFIDs have found diverse object detection and tracking applications in various fields from object detection to life detection. The RFID system consists of a reader as the transmitter and several tags as receivers. The reader will be continuously sending the interrogating pulses and the tags will respond to the signals from the reader by backscattering the inputted wave. The distance of retransmission will depend on the properties of the resonator like, the depth of scattering parameters and the Quality factor of the RFID resonators. In certain cases duplication of the resonators could double the transmission range compromising the increased size of the tag. The operation of planar RFID tags is closely related to the resonant frequency of the resonators within the tag. Resonance occurs when the electrical length of the antenna is an integer multiple of the wavelength associated with the operating frequency. The electric field characteristics of the tag has a direct impact on the read range of the RFID tag. By optimizing the design of the tag and based on the wavelength of the tag, the read range could be improved. Passive RFID tags working on backscattering principles do not have an internal power source and they utilize the energy from the electromagnetic field generated from the reader to power up and communicate. The sensing capability of these sensors is due to the high electric field when excited at the resonant frequency and is one of the important parameters that determines the range of the passive RFID tag. The electric field analysis of a printed planar 4 bit RFID tag for sensing application is discussed in the paper. The tags are excited at the respective resonant frequencies and the field variation of the excited resonator is identified. The resonators are capable of generating high electric fields thus are capable of long range communication depending upon the reader.