超宽带低相移单片六位微波数字衰减器的设计与研究

【作者】 钱桂香；

【导师】 戴永胜； 王安劳；

【作者基本信息】 南京理工大学 ， 通信与信息系统， 2008， 硕士

【摘要】 超宽带低相移单片微波数字衰减器在宽带电子对抗、相控阵雷达系统和宽带微波合成扫频信号发生器等仪器仪表中都有着广泛的应用。本文研究的超宽带单片六位微波数字衰减器插入相移小、衰减精度高,采用该电路将使相应的系统省去为校准幅度和相位所增加的额外电路,降低成本,提高可靠性,并且这种电路可以编程控制,易与计算机技术兼容。本论文主要介绍了2～18GHz超宽带低相移六位MMIC数字衰减器的原理、电路的设计、仿真优化及版图设计。文中首先探讨了微波单片集成电路中控制器件GaAsPHEMT开关的工作机理,模型的建立及电路模型参数的提取。然后介绍了数字衰减器的基本理论,并分析了几种典型数字衰减器电路拓扑结构(如T型、PI型、桥T型、开关路径型等)的工作原理。设计工具采用了Advanced Design System 2004(ADS2004),首先根据不同的衰减量确定合适的数字衰减器的电路拓扑结构,根据衰减量计算出该拓扑结构中的电阻初值,然后联接实际的微带电路对衰减精度、插入损耗、相对插入相移和输入/输出驻波比进行优化。每一位优化达到设计指标后,再将每位级联构成六位数字衰减器,进行总体仿真优化。完成电路仿真优化后初步生成每个衰减位的版图,最后进行版图的级联和设计,使其结构紧凑、占用芯片面积小、使用方便。最后设计的超宽带单片六位数字衰减器参考态插入损耗低、衰减精度高、插入相移小、输入/输出驻波低、尺寸小。在工作频带2～18GHz内,最大衰减量为31.5dB、衰减步进为0.5dB;参考态插入损耗:＜3.6dB;衰减精度典型值:±0.3dB;总插入相移:-2.018°/+2.367°;输入/输出驻波比典型值:1.30;芯片尺寸:2.93mm×1.02mm×0.1mm。各项性能均优于设计要求。更多还原

【Abstract】 Ultra broadband MMIC microwave digital attenuators with low insertion phase shift are widely used in broadband electronic countermeasures and phased-array radar scanning systems as well as in broadband microwave signal generators, and other synthetic frequency sweep instrumentations. The MMIC 6-bit digital attenuator in this paper with low insertion phase shift, high attenuation accuracy applied in system will allow the system to omit the additional circuits for calibration ,so the costs will reduced and the reliability can be improved. The digital attenuator can be controlled by program, so it’s easily compatible with computer technology.This paper mainly introduced the circuit design, layout design and simulation results of this ultra broadband 2-18 GHz MMIC 6-bit digital attenuator with low phase shift. First, the operation principle of PHEMT switch and the small-signal model parameter extraction method for PHEMT modeling are presented in the paper. Then the author described the basic theories of digital attenuators and contrasted the principle of several typical topologies for attenuators (T attenuators, PI attenuators, T-bridge attenuators, switch path attenuators).In this design, Advanced Design System 2004(ADS2004) is used as the EDA tool. After the appropriate topology is selected for each bit and initial values of the ideal resistors are calculated for different attenuation, they are all put in integrated circuits with many micro strip lines. Proper optimized functions are chosen for all optimized goals such as attenuation accuracy, insertion loss, insertion phase shift and input/output VSWR. While each bit has achieved their best states, they can be cascaded for simulation. In layout design, the chip must have compact configuration, small chip size and be easy to use.The final ultra broadband MMIC 6-bit digital attenuator has many excellent characteristics such as low referenced insertion loss, high attenuation accuracy, small insertion phase shift, low input/output VSWR, small chip size. In the operation bandwidth 2-18GHz, the attenuator has 31.5dB dynamic range stepped by 0.5dB; referenced insertion loss: <3.6dB; typical attenuation accuracy:±0.3dB; insertion phase shift: -2.018°/+2.367°; typical input/output VSWR: 1.30; chip size: 2.93mm×1.02mm×0.1mm. All these performances are better than the design requirements.更多还原