【作者】 胡汝刚；

【导师】 王均宏；

【作者基本信息】 北京交通大学 ， 通信与信息系统， 2008， 硕士

【摘要】 利用射频信号对物体进行自动识别的射频识别(Radio FrequencyIdentification,RFID)技术是一项正在迅速发展的技术,尤其是UHF频段的RFID技术发展很快。随着RFID系统工作频率的提高,天线设计变得越来越重要。本文研究了UHF频段RFID系统的天线技术,主要工作及创新点如下:首先,本文研究了标签天线及读写器天线设计的理论方法,并重点研究了标签天线设计理论。研究结果表明,为保证标签天线的基本读写距离,在设计标签天线时,需要首先考虑天线增益和标签天线到芯片的功率传输系数,提高功率传输系数的途径就是调整标签天线与芯片的输入阻抗并使它们尽可能实现共轭匹配。其次,本文研究并设计了一种低成本小型化的UHF频段RFID标签天线,天线为变形偶极子形式。可以采用调节短路线的方式调节天线的输入阻抗,本文以此方法设计的标签天线输入阻抗实部可以在30到50Ω范围内调节,虚部在150到300Ω范围内调节,可以满足天线与大多数芯片的共轭匹配要求。另外通过弯曲偶极子的两臂可以对天线进行小型化设计,本文以此方法设计的标签天线尺寸为52mm×44mm×0.5mm,相比同类型其它标签天线,尺寸减小了40%左右。另外由于采用对称设计,天线主辐射方向指向标签的正反面方向,这样便于读写器识别标签。最后本文制作了所设计的标签天线并分析了标签天线的输入阻抗测量方法。再次,本文研究并设计了一种低成本小型化的UHF频段RFID读写器天线。采用上贴片挖孔、增加介电常数的方式来减小天线的尺寸,并深入研究了天线的各个尺寸参数对天线性能的影响,指出天线性能对上表面贴片边长d、挖孔宽度e以及介电常数ε的变化比较敏感。文中最后优化的天线在2dB增益情况下,天线尺寸在110mm×110mm×3mm左右,相比较于同类型参考天线,面积减小了近70%,阻抗带宽提高75%左右,轴比带宽提高60%左右。同时还可以根据增益大小的需要调整天线的尺寸。最后本文制作了其中两组参数的读写器天线,回波损耗的测试结果与仿真结果吻合较好,验证了设计方法的有效性。更多还原

【Abstract】 Radio Frequency Identification(RFID) which uses radio frequency singals for automatic identification of objects is a rapidly developing technology, especially UHF band RFID technology. With the frequency of RFID system increasing, antenna design has become more and more important. Antenna technology on the UHF band RFID system is studied in this thesis, and the main work and innovation points include:Firstly, theoretical methods of the tag antenna and the reader antenna design are investigated and the emphasis is placed on the tag antenna. The result indicates that radiation gain and power transmission coefficient from tag antenna to chip should be considered in the first place in order to ensure the basic reading and writing distance of the tag. The way to improve power transmission coefficient is to design the tag antenna and make sure its input impedance conjugate matching to the chip input impedance.Secondly, a kind of low-cost miniaturized UHF band RFID tag antenna with the form of transformative dipole is studied and designed in this thesis. Its input impedance can be regulated by adjusting antenna short line. The real and imaginary part of tag antennas designed by the method in this thesis can be regulated from 30 to 50Ωand from 150 to 300Ωrespectively, which can meet the requirement of conjugate matching between the tag antennas and most chips. In addition, miniaturization design of the antenna can be carried out by bending two arms of the dipole. The size of the tag antenna optimized by this method in this thesis is 52mm×44mm×0.5mm and reduced by 40 percents comparing with other tag antennas of the same kind. Because of symmetrical design, the main radiation direction points to the front and back sides of the tag which makes it easy for the tag to be read by the reader. The designed tag antenna is fabricated finally and the measurement method of input impedance is analyzed.Thirdly, a kind of low-cost miniaturized UHF band RFID reader antenna, the size of which can be miniaturized by the patch hole digging and increasing the permittivity, is also studied and designed in this thesis. Furthermore, the influences on the antenna performance by all kinds of antenna parameters are further researched and that performance of the antenna is sensitive to the length of top patch side d, the width of patch dig hole e and the permittivityεis indicated. The size of the optimized antenna is about 110mm×110mm×3mm while the gain is 2dB, which size is reduced by 70 percents and bandwidth of return loss and axial ratio is increased by 75 percents and 60 percents respectively comparing with the same kind reader antenna. Meanwhile, the size can be adjusted according to the demand of gain. The designed reader antennas in two kinds of parameters are fabricated finally. The measured and the simulated results are in good agreement and validity of the design method is proved.更多还原