A Novel Dual-Antenna Structure for UHF RFID Tags

A novel dual-antenna tag structure for UHF radio-frequency identification (RFID) systems is proposed. It is formed by two linearly tapered meander dipole antennas that are perpendicular to each other and connected to the slightly modified tag chip. One of the antennas is for receiving, while the other is for backscattering. The input impedance of the receiving antenna is designed to be conjugate matched to the highly capacitive chip impedance for the maximum power transfer. Meanwhile, the backscattering antenna is alternatively terminated by an open or a short circuit to modulate the backscattered field. By making the input impedance of the backscattering antenna real-valued, the maximum differential RCS may be achieved leading to a longer read range and better reliability. With the aid of the design of experiments (DOE) technique, the proposed dual-antenna structure is designed to fit within a compact area of 32.8 × 32.8 mm² while keeping relatively low mutual coupling between the two antennas. The impedance, receiving, and backscattering performances of the proposed dual-antenna structure are measured and simulated, and they agree very well. Also, it is demonstrated that the proposed dual-antenna structure outperforms the conventional single-antenna tag design in every respect.