中文说明：
首先，建立两个模拟信号的数学模型 有用信号 干扰信号。两个信号的中心频率、信号带宽等参数由学生自己选定，要求两个信号的频谱不重叠 分别画出三个模拟信号的时域波形和频谱图；然后，根据x_a (t)的中心频率和带宽，按照奈奎斯特采样定理选择采样频率fs，分别对信号s_a1 (t)、s_a2 (t)、x_a (t)进行时域采样，得到离散信号s_1 (n)、s_2 (n)、x(n)。利用FFT算法分析离散信号的频谱，分别画出三个离散信号的时域波形和频谱图； 接着，设计数字滤波器H(z)，要求该滤波器对干扰信号s_2 (n)的衰减大于40dB。提出滤波器的设计指标，并设计滤波器，给出滤波器的设计结果，绘制滤波器的幅频特性和相频特性曲线，验证滤波器的设计结果是否达到设计指标要求；此外，选择实现数字滤波器H(z)的结构，画出滤波器结构信号流图；然后，将合成信号x(n)输入数字滤波器H(z)，按照所选择的滤波器结构，设计计算机程序计算滤波器的输出响应y(n)，画出y(n)的时域波形和频谱图。
English Description：
Firstly, the mathematical model of two analog signals is established, and the useful signal interferes with the signal. The center frequency, signal bandwidth and other parameters of the two signals are selected by the students themselves, and the spectrum of the two signals is required not to overlap, and the time-domain waveform and spectrum of the three analog signals are drawn respectively; then, according to X_ According to Nyquist sampling theorem, the sampling frequency FS is selected, and the center frequency and bandwidth of a (T) are determined_ a1 (t)、s_ a2 (t)、x_ A (T) is sampled in time domain to obtain the discrete signal s_ 1 (n)、s_ 2 (n)、x(n)。 FFT algorithm is used to analyze the spectrum of discrete signal, and the time domain waveform and spectrum diagram of three discrete signals are drawn respectively;