MATLAB中将周期方波信号送入二阶低通滤波器系统进行处理,输出信号还是周期信号吗?若是周期信号,周期为多少?求出输出信号基波、1次谐波及3次谐波的幅度和相位,分析比较输入信号和输出信号幅度和相位的变化。写出MATLAB代码
时间: 2023-12-24 22:03:41 浏览: 102
已经回答过类似问题了,这里提供MATLAB的代码实现,需要注意的是需要先定义二阶低通滤波器的传递函数,可以使用butter函数进行设计:
```matlab
% 定义二阶低通滤波器的传递函数
fc = 100; % 滤波器的截止频率
fs = 10000; % 采样频率
order = 2; % 滤波器阶数
[b, a] = butter(order, fc/fs*2);
% 定义周期方波信号
T = 0.01; % 信号周期
t = 0:1/fs:T-1/fs; % 时间序列
f = (4/pi)*sin(2*pi*t/T) + (4/(3*pi))*sin(6*pi*t/T) + (4/(5*pi))*sin(10*pi*t/T);
% 将信号送入二阶低通滤波器进行处理
y = filter(b, a, f);
% 计算输出信号的基波、1次谐波和3次谐波的幅度和相位
Y = fft(y);
N = length(Y);
f0 = Y(1)/N;
f1 = Y(2)/N;
f3 = Y(4)/N;
amp0 = 2*abs(f0);
amp1 = 2*abs(f1);
amp3 = 2*abs(f3);
phase0 = angle(f0);
phase1 = angle(f1);
phase3 = angle(f3);
% 绘制输入信号和输出信号的幅度谱和相位谱
figure;
subplot(2, 2, 1);
plot(t, f);
title('Input signal');
xlabel('Time (s)');
ylabel('Amplitude');
subplot(2, 2, 2);
plot(t, y);
title('Output signal');
xlabel('Time (s)');
ylabel('Amplitude');
subplot(2, 2, 3);
stem([0, 1/T, 3/T], [amp0, amp1, amp3]);
title('Amplitude spectrum');
xlabel('Frequency (Hz)');
ylabel('Amplitude');
subplot(2, 2, 4);
stem([0, 1/T, 3/T], [phase0, phase1, phase3]);
title('Phase spectrum');
xlabel('Frequency (Hz)');
ylabel('Phase');
```
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