Broadband and High-Gain Antenna for Frequency-Coded Chipless RFID Handheld Readers

A high-gain antenna covering 1.7-5.5 GHz based on a quasi-Yagi structure is proposed for frequency-coded chipless radiofrequency identification (RFID) handheld readers. To enhance the capacity of chipless RFID, a broadband spectrum is required. In addition, when chipless tags are arranged facing the reader, a high-gain reader antenna is desired such that detection reliability can be improved. To meet the two requirements simultaneously, we propose an antenna that uses the quasi-Yagi configuration with a broadened impedance bandwidth and large front-to-back ratio (FBR). The bandwidth improvement is achieved using a bow-tie shaped driven dipole. The enhancement of gain is obtained using optimized parameters for directors and a reflector. Simulated results indicate that the impedance bandwidth is 1.70-5.53 GHz. The broadside gain and FBR vary over the passband are 3.7-5.3 dBi and 4.8-16.8 dB, respectively. The performance of the antenna is suitable for the chipless RFID system that has a data capacity of 21 bits.