对数周期偶极子结构的新型近场均匀天线

A Novel Near-field Uniform Antenna with Log-periodic Dipole Structure

为满足超高频射频识别阅读器近场天线对宽频带内均匀场分布的需求,将同向电流环和反向电流对两种技术结合,提出了一种中心馈电的多环天线。通过4个双面微带线馈电的弯曲四元印刷对数周期偶极子天线组成圆环阵列,易于获得宽频带阻抗匹配,并有效改善圆形区域均匀磁场分布。对天线进行了加工与测试,结果表明在799~971 MHz频率范围内|S 11|<-10 dB,覆盖全球通用超高频射频识别频段。当输入功率为30 dBm,在天线上方20 cm×20 cm×15 cm内实现对标签100%的读取率,最大的读取距离为22 cm。该天线结构简单,设计灵活,可通过增加对数周期天线个数增大识别区域,通过调整弯曲的偶极子单元个数改善识别区域的均匀场分布。

In order to meet the demand of the near field antenna of ultra-high frequency radio-frequency identification(UHF RFID)reader for the uniform field distribution in the broadband application,a novel multi-loop antenna fed from the center is proposed by combining the co-current loop and the reverse current pair.Four curved four-element printed log-periodic dipole antennas fed with double-sided parallel-strip lines form a ring array,which is easy to obtain wide-band impedance matching and effectively improve the uniform magnetic field distribution in the circular region.The antenna has been fabricated and measured.The results show that|S_(11)|is less than-10 dB within the frequency range of 799~971 MHz,which covers the universal UHF RFID band.When the input power is 30 dBm,a 100%recognition rate is achieved within 20 cm×20 cm×15 cm above the antenna,and the maximum reading range is 22 cm.The antenna is simple in structure and flexible in design.The identification area can be increased by increasing the number of log-periodic antennas,while the uniform field distribution of the identified region can be improved by adjusting the number of curved dipole elements.