Tham khảo tài liệu 'current trends and challenges in rfid part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 140 Current Trends and Challenges in RFID circuit to maximize the transfer of power into and out of it. We selected an Alien s Gen 2 RFID chip which has an impedance value of 30 - 110j Q so we designed the tag antenna with the impedance value of 30 110j Q to conjugate match with the chip. In the simulation we considered both the resistivity of the materials surface roughness and configuration of the antenna. Based on the simulation result we designed a series of RFID tag antenna based on 1 and 2 series. The antenna is a 82 mm-long dipole with a short line connecting two parts as shown in Fig. 9. 36 For example the simulated impedance of the ECA antenna filled with 30 wt of silver filler is 33 108j at 915 MHz which well matches the Alien s RFID strap 30 - 110j . The calculated return loss values is -24 dB which means over 99 power is transmitted to RFID chip. We found that the -10 dB power transmission bandwidth of the antenna is 60 MHz which covers the operation frequency of North American China and Hong Kong standards. 37 Herein we use the minimum turn-on power of the reader as the index of the RFID tag antenna performance. The reader is located one meter in distance towards the RFID tag a piece of EPCglobal Class 1 Gen 2 RFID Chip is adhered to the center of the antenna . From the experimental result we can observe that the minimum turn-on power of the reader is consistent with the electrical resistivity of the ECA samples . with the increment of the resistivity of the antenna the reader needs a higher minimum turn-on power to detect the tag Fig. 12 . Therefore using the same antenna design we can adjust the content of silver filler in the ECA to cater to different requirement of read range. As for the real application of RFID technique the power out-put of the reader is often fixed to a certain value. Controlling the resistivity of the ECA can probably be a convenient way to cater to the different requirement of read range requirement. Apparently that by .
