信号分选与数字滤波.pdf

信号分选与数字滤波实验报告 刘伶 【摘要】：本实验是设计一数字化接受系统，分出具有两个位于不同频率范围的接受信号，并对输入 信号r(t)及分选出来的两路信号进行频谱分析。首先分析了输入信号类型和频谱，设计出可行的信号分选 方案，确定了信号将通过的两个滤波器的类型以及必须满足的硬性指标。然而为实现信号分选与数字滤波 的功能，我们先采用奈奎斯特律采样定律对信号进行A/D 转换，并推导了经采样的信号如何利用 FFT/DFT 变换复原的原理。接下来对于系统的性能我们采用差分方程描述，并得出其传输函数的形式以及如何由传 输函数得到一个实现的结构框图。最后，我们由巴特沃斯低通和高通滤波器的设计方法给出了两个滤波器 较为合理的指标，通过编程最终确定了 IIR滤波器传输函数的系数和表达式，画出系统的频率响应。 关键词：奈奎斯特律、FFT/DFT、信号卷积、数字滤波理论 Abstract: This experiment is to design a digital receiving system, separate with two located in different frequency range of the receive signals, and the input signal R (T) spectrum analysis and sorting out of the two signals. First analyzes the input signal type and spectrum, designed signal sorting scheme is feasible, the signal will be two types of filters and must meet the mandatory index. However, in order to realize the signal sorting and filtering function, we use Nyquist sampling theorem for A/D conversion law of signal, and the principle of how to use FFT/DFT to transform the sampled signal restoration derivation. Next to the performance of the system we use the difference equation, and obtain the transfer function in the form of the transfer function and how to get an application structure diagram. Finally, we designed by the method of Butterworth low pass and high pass filter is given in the two filter more reasonable target, through the programming and ultimately determine the coefficient and the expression of IIR filter transfer function, draw the system frequency response. Key Words: Nyquist law FFT/DFT convolution digital filtering theory 引言 数字滤波器一词出现在60 年代中期。它是对数字信号进行滤波处理以得到期望的响应 特性的离散时间系统。作为一种电子滤波器，数字滤波器与完全工作在模拟信号域的模拟滤 波器不同。数位滤波器工作在数字信号域，它处理的对象是经由采样器件将模拟信号转换而 得到的数字信号。 应用数字滤波器处理模拟信号时，首先须对输入模拟信号进行限带、抽样和模数转换。 数字滤波器输入信号的抽样率应大于被处理信号带宽的两倍，其频率响应具有以抽样频率为 间隔的周期