毫米波平面电路最新技术研究

【作者】 李小卫；

【导师】 孙晓玮；

【作者基本信息】 中国科学院研究生院（上海微系统与信息技术研究所） ， 2002， 硕士

【摘要】 无线通信技术的飞速发展大大推动了微波、毫米波技术的民用化研究，毫米波平面电路作为毫米波技术的重要组成部分，近年来出现了很多新的技术，例如多芯片组装（MCM）技术，微电子机械（MEMS）技术，片上系统（SOC），电磁晶体（EBG）等，这些新技术和工艺的出现大大提高了毫米波雷达和通讯系统的整体性能，减少了系统的功耗和体积。本文的研究围绕35GHz微带阵列天线，毫米波微机械开关和光子带隙滤波器和天线三个方面，主要的研究内容如下： 1．简要介绍了毫米波防撞雷达系统的研究概况，特别回顾了毫米波防撞雷达天线的发展过程；详细介绍了射频微机械开关的主要结构和工作原理；详细介绍了光子晶体的研究背景、原理和应用。 2．基于毫米波防撞雷达单目标探测对天线窄波束、高增益、小型化和平面化的要求，重点研究了微带阵列天线的设计方法，设计了微带线阵列天线、微带串馈面阵列和微带并馈面阵列天线，微带并馈8×8阵列天线的波束宽度为±5°，副瓣电平为-17dB，增益达到22dBi；并首次将微带阵列天线在SAE-100防撞雷达系统上使用，采用该8×8阵列天线的雷达系统混频得到很好的回波信号，在距离为2米时信号幅度达到±0.03V；实验结果表明35GHz微带并馈8×8阵列天线能满足防撞雷达单目标探测对天线的指标要求，其性能可以与现在使用的喇叭天线相比，这将为防撞雷达的小型化和实用化奠定基础。 3．介绍了毫米波微机械开关的工作原理和主要结构，重点研究了一种新型的毫米波微机械开关—单刀双掷开关，利用等效电路优化了其主要参数C_on，C_off，C_on/C_off和R的取值；研究了不同材料时桥梁的下拉电压的变化；详细给出了微机械开关的工艺过程，采用的腐蚀方法制作空气桥工艺，可以大大提高空气桥的成品率，解决了毫米波微机械开关制作中的关键难题，最后给出了实验得到的微机械开关的实物照片和测试结果。 4．共面波导（CPW）线是被广泛用于毫米波平面电路中的传输线，研究低损耗的CPW传输线对毫米波平面电路技术的发展具有重要意义。本文深入 摘要 研究了减少共面波导CPW)传输线损耗的方法，实验结果表明采用高阻 GaAs材料能将CPW线在毫米波频段的传输损耗减小到0石dB／mm以 下；同时，对于相同衬底材料的传输线，将金属的厚度增加到趋肤深度 的4．5倍，以及适当的腐蚀掉传输线间的衬底材料将分别减少0二dB／llun 的传输损耗；对于低阻出衬底的传输线而言，同时采用Polyimide和加 厚传输线金属两种方法，传输线能减少2—3dB的损耗。这些研究将为 降低 RF IC的成本，减少其损耗提供有价值的参考。 5．光子晶体是80年代末在研究抑制自发辐射时提出的新概念和新材料， 美国的《科学》杂志在曾将光子晶体列为世界六大研究热点之一。光子 晶体提出时应用的范围是光学频段，但是由于制备方面的困难，近年来， 基于微电子工艺的微波、毫米波频段的光子晶体材料（又叫电磁晶体） 得到了广泛的研究。本文的研究包括微带光子带隙滤波器和光子晶体天 线，设计的三角变化微带光子带隙滤波器，表现出良好的滤波特性，其 中心频率10GHz处的衰减可达30dB以上，而带外衰减则小于3dB，并 且在20GHZ处没有谐振峰出现；该滤波器的最大优点在于能在信号传 输的过程中直接将各种高次谐波滤掉，而不需要增加滤波器件，对于减 小集成电路和各种射频系统的体积具有实际意义。利用光子晶体改善微 带阵列天线的电学特性，还没有相关的工作报道，本文比较了基于光子 带隙衬底的并馈微带阵列天线与无带隙衬底的同一天线的S参数，结果 发现，采用带隙结构衬底的阵列天线，其谐波能得到比较好的抑制。更多还原

【Abstract】 With the rapid development of wireless communication technology, the civilization research of microwave and millimeter-wave technology has been strengthened greatly. Millimeter-wave planar circuit is one important part of millimeter-wave technology. In recent years, many new technologies, such as MCM, MEMS, SOC, EBG, etc, have been applied into the millimeter-wave planar circuits. All these new technologies have improved the performance of the civilian millimeter-wave radar and RF communication system as well as induced the volume and power consumption of these systems. The research of this dissertation focuses on three aspects: the microstrip array antenna of 35GHz, millimeter-wave MEMS switch and the Photonic Bandgap(PBG) filter and microstrip array antenna on PBG substrate. The main context of this dissertation includes:1. The situation of millimeter-wave automobile collision warning radar (CWR) is introduced, especially pictured the history of antenna of CWR. The structures and principle of RF MEMS switch are introduced in detail. It is provided about the background, principle and application of Photonic Crystal.2. Based on the requirement for the antenna of CWR, such as thin beam, high gain, little volume and planar structure etc, the design method of microstrip array antenna is research especially. Three different kinds of array antenna are designed, including microstrip linear array antenna, series-fed rectangle array antenna and shunt-fed rectangle array antenna. As the result of experiment, the beamwidth of 8 8 shunt-fed array antenna is 5 , side lobe level is 17dB and the gain is 22dBi. It is the first time to apply the microstrip array antenna in SAE-100 radar system. The returning wave is good, which has the amplitude of 0.03V, as the distance is 2m.. The results show that this shunt-fed array antenna can be used as the CWR antenna for a single object detecting. The excellent performance of SAE-100 with microstrip antenna is one of the important steps for the miniaturization and practical application of this system.3. The principle of millimeter-wave MEMS switch is introduced and two different structures of MEMS switch are given. A new millimeter-wave MEMS switch, single pole double throw (SPDT) MEMS switch, is designed. Using the HP ADS, the author has optimized the value of Con, Coff, Con/Coff and R, which are the main parameters of the RLC circuit of SPDT MEMS switch. At the same time, the relationship between the action voltage and the material of air bridge is analyzed. A new method, the wet eroding, is applied to fabricate the air bridge. This method can improve the rate of finished product of air bridge. The picture and tested results is provided in this article.4. The Coplanar Waveguide (CPW) transmission line is used commonly in the millimeter-wave planar circuit. It is very valuable to research the low-loss CPW line for millimeter-wave planar circuit. In this article, some novel methods are applied to reduce the transmission loss of CPW line. As the results of experiment, the loss of CPW on high-resistivity GaAs is less than 0.6dB/mm. On the other hand, for the CPW on the same substrate, there are two means to cut down the loss, the first is to electroplate the metal of CPW to 4-5 times thickness of skin depth; the second is to erode somewhat the substrate material between the metals. All will reduce the loss about 0.2dB/mm respectively. For the CPW line on low-resistivity Si, polyimide is used to reduce the loss as well as electroplate the metal. The transmission loss of CPW on low -resistivity Si, which is applied the two means at the same time, will be 2-3dB than the loss of the line without any means. The research can provide reference for cutting down the cost and power consumption of RF IC.5. Photonic Crystal (PC), which is invented to inhibit the spontaneous emission in the end of 1980s, is a new kind of concept and material. Science has ranked photonic crystal as one of the six most important fields. A更多还原