应用于UHF频段的磁介材料及读写器天线研究

发布时间：2018-03-16 11:46

  本文选题：天线小型化　切入点：宽频化　出处：《电子科技大学》2014年硕士论文　论文类型：学位论文

【摘要】：近年来物联网技术的应用已经深入到各个领域,射频识别(RFID)作为物联网的关键技术得到了快速发展,其系统内部的硬件尺寸变得越来越小,如何实现RFID读写器天线的小型化变得至关重要。除了结构上的调整,引入低损耗的磁介电材料替代传统的介质基板可以很好地实现天线的小型化,同时引入的磁损耗还能够拓宽天线阻抗带宽。实验证明,在获得相同小型化的情况下,采用磁介电材料所获得的阻抗带宽将优于高介电常数基板。为此,本论文较为系统地研究了一种应用于超高频(UHF)RFID频段(840~960 MHz)的低损耗磁介电材料,并基于该材料设计并制作了两种不同结构的读写器天线,以验证试验方案的可行性。一方面,从材料入手,对Co2Z铁氧体进行研究,逐步分析了缺铁、铝替代铁和掺杂BBSZ玻璃等方案对材料性能的影响。实验发现,当缺少两个铁原子时,材料具有较好的电磁性能。然后,进行了铝替代铁实验方案,Al3+替代Fe3+有效地抑制了Fe2+的出现以降低材料的磁介电损耗;随着铝替代量的增加,材料的磁介电损耗均呈现先降低后增加的趋势,在铝替代量x为1.6,980℃烧结下材料的损耗达到最低。最后,基于铝替代铁方案进行了掺杂BBSZ玻璃的实验以提高材料的烧结致密化。研究发现,随着BBSZ含量的增加,材料的磁导率和介电常数均有明显的提高,过多的掺杂量会使磁导率略微下降;在BBSZ含量为3.0 wt%,烧结温度为950℃时材料具有最优性能。另一方面,基于自制的材料设计并制作了两种不同类型的RFID读写器天线。第一种天线采用传统的微带天线结构-圆环形辐射贴片,在偏离馈电45°方向内环开槽实现圆极化辐射,该天线的中心频率约为914 MHz,S11小于-10 dB时天线的阻抗带宽达到48 MHz,但其增益较低。针对第一种天线增益较低的问题,在天线正上方悬置了一个开窗的金属层设计了第二种天线,该天线采用开路微带线进行馈电。测试结果显示,在中心频率915 MHz处天线的增益达到3.6 dBi,阻抗带宽达到29 MHz,该天线的辐射方向图良好。这两种设计方案很好地兼顾了RFID读写器天线在小型化和宽频带方面的技术要求,第二种方案还针对第一种方案天线增益较低的问题作出了结构上的改进设计。
[Abstract]:In recent years, the application of Internet of things technology has been deep into various fields. Radio frequency identification (RFID), as the key technology of the Internet of things, has been developed rapidly, and the hardware size of the system has become smaller and smaller. It is very important to realize the miniaturization of the RFID reader antenna. Besides the structural adjustment, it is possible to miniaturize the antenna by introducing the magnetic dielectric material with low loss instead of the traditional dielectric substrate. At the same time, the magnetic loss can also widen the impedance bandwidth of the antenna. The experimental results show that the impedance bandwidth obtained by using magnetic dielectric material is better than that of high dielectric constant substrate under the same miniaturization. In this paper, a low loss magnetodielectric material used in UHF UHFU RFID band is studied systematically. Based on this material, two kinds of reader antennas with different structures are designed and fabricated to verify the feasibility of the experimental scheme. The effects of iron deficiency, aluminum substitution for iron and doped BBSZ glass on the properties of Co2Z ferrite were studied. It was found that the material had better electromagnetic properties when two iron atoms were missing. The experimental scheme of aluminum substitution for iron, Al3 instead of Fe3, effectively inhibited the appearance of Fe2 in order to reduce the magnetic dielectric loss of the material, and with the increase of aluminum substitution, the magnetic dielectric loss of the material decreased first and then increased. The loss of the material is the lowest when the aluminum substitution x is 1.6 ~ 980 鈩，

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