使用低通滤波器从含有噪声的信号中提取有用的正弦波

(见实验指导书 实验九 数字滤波器中的第一题)

目的：用数字滤波器从含有高频噪声的采样数据中提取正弦信号。

要求：①输入信号为一正弦波，并加入一个白噪声的干扰来模拟信号传输中的随机干扰信号（用以模拟含有噪声采样序列）。

（模拟含有噪声采样序列具体可用正弦波信号叠加高频噪声来实现，为了使滤波效果明显，本实验的高频噪声是用高频均匀分布白噪声（Uniform）通过Butterworth高通滤波器过滤生成的，高通滤波器的截止频率设为10倍输入信号频率。）

②在程序中设计一个低通巴特沃斯滤波器，以滤除信号中的噪声分量，提取输入的正弦波信号 。

③可调节信号滤波器的截止频率和阶数，可显示滤波前与滤波后的时域信号。

④给出滤波前与滤波后的频谱特性的显示。

-Using low pass filter　extracting useful sine wave signal containing noise(see experiment instruction digital filter in the first nine questions)Objective: to use digital filter　sampling data extract containing high frequency noise sine signal.Requirements: (1) the input signal is a sine wave, and add a white noise interference to simulate the random disturbance signal of the signal transmission (to simulate contains noise sampling sequence).(simulated the sampling sequence contains noise available sine wave signal superposition of high frequency noise, in order to make the filtering effect is obvious, the experiment of high frequency noise is Uniform distribution with high frequency white noise (Uniform) by Butterworth high-pass filter to filter generated, high-pass filter cutoff frequency set to 10 times the size of the input signal frequency.)(2) in the program design a low-pass butterworth filter, in order to filter out the noise in the signal component, extract the input sine wav