import numpy as np
import matplotlib.pyplot as plt
from scipy.signal import hilbert
from scipy import signal
from matplotlib.pylab import mpl
mpl.rcParams['font.sans-serif'] = ['SimHei'] # 显示中文
mpl.rcParams['axes.unicode_minus'] = False # 显示负号
# 生成调制信号
fs = 1000 # 采样频率
t = np.arange(0, 1, 1/fs) # 定义时间序列
baseband_signal = 2 * np.sin(2*np.pi*10*t) # 频率设为10Hz
# 生成载波信号
fc = 100 # 载波信号频率
carrier_signal = 1/2 * np.sin(2*np.pi*fc*t) # 调制信号幅度为0.5
# 进行调制
modulated_signal = baseband_signal * (1 + carrier_signal)
# 进行解调
analytic_signal = hilbert(modulated_signal) # 进行希尔伯特变换
amplitude_envelope = np.abs(analytic_signal) # 得到包络线
demodulated_frequency_unfiltered = modulated_signal / amplitude_envelope
b, a = signal.butter(4, [2*50/fs], 'lowpass') # 4阶带通滤波器
demodulated_frequency = signal.filtfilt(b, a, demodulated_frequency_unfiltered)
###测试###
def to_fft(data,i,j):
freq = np.fft.fftfreq(len(data), 1/fs) # 自动生成频率
y = np.fft.fft(data) # FFT变换
y = 2*np.abs(y)/fs # 归一化,能量集中处理
y_ed = y * 2 / fs #*2能量集中化,/N归一化
plt.subplot(4, 2, i)
plt.plot(freq, y_ed)
plt.title('频域')
plt.xlim(0,j)
to_fft(baseband_signal,2,150)
to_fft(carrier_signal,4,150)
to_fft(demodulated_frequency_unfiltered,6,150)
to_fft(demodulated_frequency,8,150)
###测试###
# 绘制信号图形
plt.subplot(4, 2, 1)
plt.plot(t, baseband_signal)
plt.title('Baseband Signal')
plt.subplot(4, 2, 3)
plt.plot(t, carrier_signal)
plt.title('Carrier Signal')
plt.subplot(4, 2, 5)
plt.plot(t, demodulated_frequency_unfiltered)
plt.title('demodulated_frequency_unfiltered')
axes_1 = plt.subplot(4, 2, 7)
plt.plot(t, demodulated_frequency,label='demodulated_frequency')
plt.title('demodulated_frequency')
axes_1.legend()
plt.tight_layout()
plt.show()
这是自己改了下的 |