`scipy.signal._waveforms:square`

Signature

def square(t, duty = 0.5)

Return a periodic square-wave waveform.

The square wave has a period 2*pi, has value +1 from 0 to 2*pi*duty and -1 from 2*pi*duty to 2*pi. duty must be in the interval [0,1].

Note that this is not band-limited. It produces an infinite number of harmonics, which are aliased back and forth across the frequency spectrum.

t : array_like: The input time array.
duty : array_like, optional: Duty cycle. Default is 0.5 (50% duty cycle). If an array, causes wave shape to change over time, and must be the same length as t.

A 5 Hz waveform sampled at 500 Hz for 1 second:

import numpy as np
from scipy import signal
import matplotlib.pyplot as plt
t = np.linspace(0, 1, 500, endpoint=False)

✓

plt.plot(t, signal.square(2 * np.pi * 5 * t))
plt.ylim(-2, 2)

✗

(-2.0, 2.0)

A pulse-width modulated sine wave:

plt.figure()

✗

<Figure size 640x480 with 0 Axes>

sig = np.sin(2 * np.pi * t)
pwm = signal.square(2 * np.pi * 30 * t, duty=(sig + 1)/2)

✓

plt.subplot(2, 1, 1)
plt.plot(t, sig)
plt.subplot(2, 1, 2)
plt.plot(t, pwm)
plt.ylim(-1.5, 1.5)

✗

(-1.5, 1.5)