学ぶ Filtering Signals with Python | Signal Processing for Electrical Engineers

Python for Electrical Engineers

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Digital filtering is a fundamental technique in signal processing that allows you to modify or enhance electrical signals by removing unwanted components such as noise. In electrical engineering, signals captured from sensors or communication systems often contain random fluctuations or interference that can obscure the true information. Digital filters are algorithms that process these signals to suppress noise and improve clarity, making them essential for reliable measurements, control systems, and data analysis.


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import numpy as np

def moving_average(signal, window_size):
    return np.convolve(signal, np.ones(window_size)/window_size, mode='valid')

# Example usage:
np.random.seed(0)
signal = np.random.normal(0, 1, 100)  # Simulated noisy signal
filtered_signal = moving_average(signal, window_size=5)
print(filtered_signal[:10])  # Show first 10 filtered values

A moving average filter works by replacing each point in a signal with the average of its neighboring values over a fixed window. This approach smooths out rapid fluctuations caused by noise while preserving the general trend of the original signal. By averaging adjacent points, the filter reduces the impact of outlier values, resulting in a cleaner, more stable signal. However, it can also slightly blur sharp transitions or edges in the data, so the choice of window size is important: a larger window provides more smoothing but may reduce signal detail.


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import matplotlib.pyplot as plt

# Generate a noisy sine wave
t = np.linspace(0, 2*np.pi, 200)
clean_signal = np.sin(t)
noise = np.random.normal(0, 0.3, t.shape)
noisy_signal = clean_signal + noise

# Apply moving average filter
window_size = 10
filtered_signal = moving_average(noisy_signal, window_size)

# Adjust time axis for filtered signal
t_filtered = t[(window_size-1):]

# Plot results
plt.figure(figsize=(10, 5))
plt.plot(t, noisy_signal, label='Noisy Signal', alpha=0.6)
plt.plot(t, clean_signal, label='Original Signal', linestyle='--')
plt.plot(t_filtered, filtered_signal, label='Filtered Signal', linewidth=2)
plt.legend()
plt.xlabel('Time')
plt.ylabel('Amplitude')
plt.title('Moving Average Filter Applied to Noisy Sine Wave')
plt.show()

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セクション 2. 章 4

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セクション 2. 章 4

Filtering Signals with Python

1. What is the purpose of a moving average filter?

2. How does filtering improve signal quality?

3. What are some real-world applications of digital filters?