As part of the general identification procedure, radio frequency identification (RFID) is an essential field of research in the modern industrial automation. Radio frequency identification is among the most technically advanced methods of controlling, detecting, and tracking items and moving information efficiently with an item along its lifespan. This project presents an intelligent 2 GHZ beam-scanning antenna array using nonlinear signal processing for RFID reader. A high-resolution two-element antenna array is demonstrated using nonlinear signal processing of output signals of the two antennas. The basic principle of this method is to convert the output signal of each antenna into a train of very short pulses and to extract a time delay between the two pulse trains by correlation. The input signals are first downconverted to a low IF frequency and then a nonlinear signal processing can be achieved by taking the amplitude and phase delay of the downconverted signals and simulated using Advance Design System (ADS). An experimental downconverting part, which is the RF front end part was designed and simulated using ADS and built, and the general principle of nonlinear signal processing is demonstrated using software ADS. The downconverting circuit is built up using commercially available devices and ICs. This RF downconverting system is fabricated on low dielectric constant substrate FR-4 and the discrete components are to be soldered onto the (Printed Circuit Board (PCB). With two dipole antennas spaced at half of a wavelength, the “beam direction” of the receiver can be scanned over ±60˚. This system successfully steer the beam to a signal at φ from broadside. Signal received by one of the antenna will experience phase lag or delay compare to the signal received by the other antenna depending on which direction the signal is coming from. When delay is added to one of the channel during simulation, an equivalent delay between the signals of a plane wave received by the two antennas is compensated. Consequently, the maximum signal is received at the respective angle of the incident wave. Adjusting delay in the other channel “scans” the angle of the other side. Using the information of how much delay we inserted we can calculate the direction of arrival (DOA) of the signal. Although this arrangement works only for single incident wave, applications could be the tracking of vehicles or persons carrying a transmitter.
SMART ANTENNA ARRAY FOR RADIO FREQUENCY IDENTIFICATION (RFID) APPLICATION_Cheah Yoon Fatt_E3_2007_875002781_NI