液晶微带无源器件的特性研究

发布时间：2018-07-17 08:14

【摘要】：在无线通信领域,能够实现频率的连续可调的器件受到越来越多的重视,频率调节的方案一般有三类:机械驱动、集成电子器件以及可调材料。其中可调材料能够实现连续的频率调节。与其他可调材料相比,液晶在更高频段具有低损耗、灵活连续可调等优点,且它具有较低的偏置电压,并能够满足低介电常数的要求等优势。在电场作用下液晶的介电率呈一定分布状态,已有的微波及毫米波频段的液晶器件研究成果未能考虑到这一分布的影响,本文从液晶和微波的相关理论出发,仿真研究液晶微带器件的频率可调特性,并做出实物对仿真结果进行验证。具体研究内容如下:1)采用数值方法计算液晶分子指向矢分布得到介电率分布,建立液晶微带线模型,代入液晶的介电率各向异性分布,研究其对微带线模式分布和传输特性所产生的影响。仿真结果表明液晶介电率的分布特性使得传输线的反射系数减小,谐振频率也稍有降低。2)基于液晶的介电率电可调特性和开路?/2传输线谐振器原理,利用CST仿真软件设计了一个Ka波段液晶谐振器,仿真得到其固有谐振频率为33.46GHz,加电调制后谐振频率移动至31.59GHz。在固有谐振频率处插入损耗为-1.56dB,回波损耗为-23.5dB,回波损耗小于-20dB的频带宽度约为370MHz。仿真结果表明在液晶的介电率调节量为0.4时,可以引起谐振器谐振频率连续移动的范围为1.87GHz,频率调节量为5.6%。3)实验研究基于液晶的微带器件的研制方法。研究了两种方案:玻璃基板光刻和印制电路高频板。分析了两种方案各自的利弊,最终按照印制电路板方案进行了基于液晶的谐振器的制作,并且利用矢量网络分析仪测试了其传输参量,测试结果表明在未施加电压时谐振器谐振频率为34.5GHz,插入损耗为-6.6dB,回波损耗为-15.3dB,结果与理论仿真结果基本吻合。
[Abstract]:In the field of wireless communication, more and more attention has been paid to the continuously adjustable devices which can realize frequency. There are generally three kinds of schemes for frequency regulation: mechanical drive, integrated electronic devices and tunable materials. The adjustable material can realize continuous frequency regulation. Compared with other tunable materials, liquid crystal has the advantages of low loss, flexible and continuous tunable in higher frequency band, low bias voltage, and can meet the requirements of low dielectric constant. Under the action of electric field, the dielectric rate of liquid crystal is in a certain distribution state. The existing research results of microwave and millimeter wave liquid crystal devices fail to take into account the influence of this distribution. In this paper, we proceed from the theory of liquid crystal and microwave. The frequency tunable characteristics of liquid crystal microstrip devices are simulated and the simulation results are verified. The specific research contents are as follows: (1) the dielectric distribution of liquid crystal molecules is calculated by numerical method. The liquid crystal microstrip line model is established and the anisotropic distribution of the dielectric rate of liquid crystal is substituted. Its influence on the distribution and transmission characteristics of microstrip lines is studied. The simulation results show that the reflection coefficient and resonant frequency of the transmission line are reduced by the distribution of the dielectric rate of the liquid crystal, and the resonant frequency is also slightly reduced.) based on the dielectric tunable characteristic of the liquid crystal and the principle of the open-circuit / 2 transmission line resonator, A Ka-band liquid crystal resonator is designed by using CST simulation software. The inherent resonant frequency is 33.46 GHz and the resonant frequency is shifted to 31.59 GHz after electrified modulation. The insertion loss at the natural resonant frequency is -1.56 dB, the echo loss is -23.5 dB, and the band width of which the echo loss is less than -20 dB is about 370 MHz. The simulation results show that when the dielectric rate of liquid crystal is 0.4, the range of resonant frequency continuous shift is 1.87 GHz and the frequency regulation is 5.6.3) the method of microstrip device based on liquid crystal is studied experimentally. Two schemes are studied: glass substrate lithography and high frequency printed circuit board. The advantages and disadvantages of the two schemes are analyzed. Finally, the LCD based resonator is fabricated according to the PCB scheme, and the transmission parameters are tested by using the vector network analyzer. The results show that the resonant frequency of the resonator is 34.5 GHz, the insertion loss is -6.6 dB, and the echo loss is -15.3dB. the results are in good agreement with the theoretical simulation results.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN629.1

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