带宽可调十四阶开关电容带通滤波器

发布时间：2018-10-13 15:12

【摘要】：本课题是关于滤波器处理模拟信号的设计。课题首先详细介绍了开关电容电路的工作方式,从典型连续时间结构的相关知识进行引入介绍,针对开关电容电路的剖析和滤波器非理想因素分别加以探讨,得到较为实际的解决办法,最终提出了可行的带通结构方案:根据带通滤波器的带宽须实现连续可调的要求,而且还要达到所需的衰减速度,参考带内纹波等技术指标选取合适结构,由这些核心的指标参数确定了以级联的形式来实现十四阶带通滤波器。结构的确定需要可行性的验证。在Matlab中进行系统级的建模,确定高通滤波器部分和低通滤波器部分的结构,得到相应的传递函数,通过代码的形式得到各级的系数,并进行调整优化。整体设计是差分输入差分输出的形式,能够使输出范围较单端形式扩大二倍,而且较为明显的压制整个滤波器的共模噪声。非理想因素的探讨主要侧重以下几点:首先,开关的导通电阻在系统中引入了热噪声,影响信号的传递,恶化了带内纹波;其次,版图设计得到的电容与仿真参数不匹配,造成实际的滤波器传递函数变化;最后,实际运放受有限的增益、带宽和压摆率的限制,这会影响到积分器的工作性能及精度。按照课题要求,选用级联的形式构建十四阶的开关电容带通滤波器,以便达到60dB/倍频的阻带衰减速度。根据由Matlab验证得到并优化的全局系数以后,进行滤波器的晶体管级电路设计,晶体管级电路的设计和仿真采用的是Cadence环境下的华虹0.35um工艺,完成每一部分的晶体管级设计及验证,最终得到整个设计的版图结构,最后进行版图的后仿真,验证整个设计从理论到实现的正确性。前仿真得到:通带内增益为71.77dB,上升和下降的阻带衰减速度分别为64.15dB/倍频和61.73dB/倍频,带内纹波为最小低至75mdB,满足设计要求。在完成版图以后进行了后仿真,验证了通带频率信号可完整通过。
[Abstract]:This topic is about the filter processing analog signal design. Firstly, the working mode of switched capacitor circuit is introduced in detail, and the related knowledge of typical continuous time structure is introduced. The analysis of switched capacitor circuit and the non-ideal factor of filter are discussed respectively. A practical solution is obtained, and a feasible band-pass structure scheme is put forward: according to the bandwidth of the band-pass filter, the continuous tunable requirement is achieved, and the desired attenuation speed is achieved. According to the technical parameters such as band ripple, the appropriate structure is selected, and the 14th order band-pass filter is implemented by cascading through these core parameters. The determination of the structure requires verification of its feasibility. The system level modeling is carried out in Matlab, the structure of the high pass filter and the low pass filter is determined, the corresponding transfer function is obtained, and the coefficients of each level are obtained by the form of code, and the adjustment and optimization are carried out. The whole design is the form of differential input and differential output, which can enlarge the output range twice as much as the single end form, and obviously suppress the common mode noise of the whole filter. The discussion of non-ideal factors mainly focuses on the following points: first, the on-resistance of the switch introduces thermal noise in the system, which affects the signal transmission, and worsens the in-band ripple; secondly, the capacitance obtained by the layout design does not match the simulation parameters. Finally, the actual operational amplifier is limited by limited gain, bandwidth and swinging rate, which will affect the performance and accuracy of the integrator. According to the requirements of the project, the 14th order switched capacitor bandpass filter is constructed in order to achieve the stopband attenuation speed of 60dB/ frequency doubling. According to the global coefficient verified and optimized by Matlab, the transistor level circuit of filter is designed. The design and simulation of transistor level circuit adopt Huahong 0.35um process under Cadence environment. Finally, the layout structure of the whole design is obtained. Finally, the post-simulation of the layout is carried out to verify the correctness of the whole design from theory to implementation. The results of pre-simulation show that the in-band gain is 71.77 dB, the up and down stopband attenuation speeds are 64.15dB/ doubling and 61.73dB/ doubling respectively, and the band ripple is as low as 75mdB, which meets the design requirements. After completing the layout, a post-simulation is carried out to verify that the passband frequency signal can pass through completely.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN713

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