Signal Processing with Python GUI: Part 3

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Tutorial Steps To Create GUI For Noisy Signal

At this point, you need to do some modifications to make efficient code in main_fft.py. Rename it as main_fft2.py. 

You need to add two additional parameters in show_fft() function. Those parameters are used to reference QWidget object:

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def show_fft(self, h, qwidget1, qwidget2): wc = float(self.leCutOff.text()) N = int(self.leFFTLength.text()) M = int(self.leSignalRange.text()) wc = wc*pi # widgetFFTAbs # get entire frequency domain w,Hh = signal.freqz(h,1,whole=True, worN=N) wx = fft.fftfreq(len(w)) # shift to center for plotting qwidget1.canvas.axis1.clear() qwidget1.canvas.axis1.plot(w-pi,abs(fft.fftshift(Hh))) qwidget1.canvas.axis1.axis(xmax=pi/2,xmin=-pi/2) qwidget1.canvas.axis1.vlines([-1.1,1.1],0,1.2,\ color='g',lw=2.,linestyle='--',) qwidget1.canvas.axis1.hlines(1,-pi,\ pi,color='g',lw=2.,linestyle='--',) qwidget1.canvas.axis1.annotate(r'$\omega$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=22) qwidget1.canvas.axis1.set_ylabel(r"$|H(\omega)| $",fontsize=22) qwidget1.canvas.axis1.set_title('Absolute FFT Graph') qwidget1.canvas.axis1.set_facecolor('khaki') qwidget1.canvas.axis1.grid() qwidget1.canvas.draw() # widgetFFTLog # get entire frequency domain w,Hh = signal.freqz(h,1,whole=True, worN=N) wx = fft.fftfreq(len(w)) # shift to center for plotting qwidget2.canvas.axis1.clear() qwidget2.canvas.axis1.plot(w-pi,20*log10(abs(fft.fftshift(Hh)))) qwidget2.canvas.axis1.axis(ymin=-40,xmax=pi/2,xmin=-pi/2) qwidget2.canvas.axis1.vlines([-wc,wc],10,\ -40,color='g',lw=2.,linestyle='--',) qwidget2.canvas.axis1.hlines(0,-pi,\ pi,color='g',lw=2.,linestyle='--',) qwidget2.canvas.axis1.annotate(r'$\omega$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=22) qwidget2.canvas.axis1.set_ylabel(r"$20\log_{10}|H(\omega)| $",\ fontsize=18) qwidget2.canvas.axis1.set_title('Log Absolute FFT Graph') qwidget2.canvas.axis1.set_facecolor('khaki') qwidget2.canvas.axis1.grid() qwidget2.canvas.draw()

Add two more Radio Button widgets. Set their text properties to Noise and None and set their objectName properties as rbNoise and rbNone. The modified gui_fft.ui is shown in below.

You need to use a global variable which will be use as return value in show_graph(), show_chirp(), show_sawtooth(), show_square(), and show_sweep_poly() as follows:

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def show_graph(self): global y wc = float(self.leCutOff.text()) N = int(self.leFFTLength.text()) M = int(self.leSignalRange.text()) wc = wc*pi # widgetSignal n = arange(-M, M) h = wc/pi * sinc(wc*(n)/pi) mpl.style.use('seaborn') # Noise if self.rbNoise.isChecked(): y = y + np.random.randn(len(h)) * 0.1 else: y = h self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.stem(n,y,\ basefmt='r-',use_line_collection=True) self.widgetSignal.canvas.axis1.annotate('$n$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', xycoords='axes fraction', \ textcoords='offset points', fontsize=20) self.widgetSignal.canvas.axis1.set_title('Stem Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y

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def show_chirp(self): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) f_start = float(self.leFStart.text()) f_end = float(self.leFEnd.text()) # widgetSignal t = linspace(x_start, x_end, 5001) w = chirp(t, f0=f_start, f1=f_end, t1=10, method='linear') # Noise if self.rbNoise.isChecked(): y = w + np.random.randn(len(w)) * 0.1 else: y = w self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.plot(t,y,linewidth=3.0) self.widgetSignal.canvas.axis1.annotate('$sec$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', xycoords='axes fraction', \ textcoords='offset points', fontsize=20) self.widgetSignal.canvas.axis1.set_title('Chirp Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y

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def show_sawtooth(self): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) # widgetSignal t = linspace(x_start, x_end, 5001) w = signal.sawtooth(2 * np.pi * 5 * t) # Noise if self.rbNoise.isChecked(): y = w + np.random.randn(len(w)) * 0.1 else: y = w self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.plot(t, y,linewidth=3.0) self.widgetSignal.canvas.axis1.annotate('$sec$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', xycoords='axes fraction', \ textcoords='offset points', fontsize=20) self.widgetSignal.canvas.axis1.set_title('Chirp Graph') self.widgetSignal.canvas.axis1.set_title('Sawtooth Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y

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def show_square(self): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) # widgetSignal t = linspace(x_start, x_end, 500, endpoint=False) w = signal.square(2 * pi * 2 * t) # Noise if self.rbNoise.isChecked(): y = w + np.random.randn(len(w)) * 0.1 else: y = w self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.plot(t, y, linewidth=3.0) self.widgetSignal.canvas.axis1.annotate('$sec$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', \ fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', \ xycoords='axes fraction', textcoords='offset points', \ fontsize=20) self.widgetSignal.canvas.axis1.set_title('Square Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y

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def show_sweep_poly(self): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) # widgetSignal p = np.poly1d([0.025, -0.36, 1.25, 2.0]) t = np.linspace(x_start, x_end, 5001) y = signal.sweep_poly(t, p) # Noise if self.rbNoise.isChecked(): y = y + np.random.randn(len(y)) * 0.1 else: y = y self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.plot(t, y, linewidth=3.0) self.widgetSignal.canvas.axis1.annotate('$sec$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', \ fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', \ xycoords='axes fraction', textcoords='offset points', \ fontsize=20) self.widgetSignal.canvas.axis1.set_title('Sweep Poly Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y

Run main_fft2.py. Click on Noise radio button, then choose one of signals. You will see the noisy version of each signal as shown in figures below.

Tutorial Steps To Create GUI For Noisy Signal Filtering

In gui_fft.ui, add one Combo Box widget and set its objectName property to cbFiltering. Populate this widget with two items by double clicking on the widget as shown in figure below.

Then, add two Label widgets on the form and set their text properties to pass band freq and stop band freq.

Next, add two Line Edit widgets and set their objectName properties to lePassBand and leStopBand.

Add three Widgets from Containers panel and set their objectName properties to widgetOutput, widgetFFTAbsFiltered, and widgetFFTLogFiltered.

Promote the three Widgets to gui_fft class that has been created before. The newly modified version of gui_fft.ui is shown in below.

The Object Inspector window is shown in figure below.

Define butter_filter() function to apply butterworth filtering on input signal as follows:

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def butter_filter(self, param): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) t = linspace(x_start, x_end, len(y)) pass_band = float(self.lePassBand.text()) stop_band = float(self.leStopBand.text()) #Butterworth filtering sos = signal.butter(stop_band, pass_band, \ param, fs=1000, output='sos') filtered = signal.sosfilt(sos, y) self.widgetOutput.canvas.axis1.clear() self.widgetOutput.canvas.axis1.plot(t, filtered) self.widgetOutput.canvas.axis1.set_ylabel("$h$",fontsize=22) self.widgetOutput.canvas.axis1.set_xlabel("$sec$",fontsize=22) self.widgetOutput.canvas.axis1.set_title('Butterworth Filtered Signal') self.widgetOutput.canvas.axis1.set_facecolor('lightblue') self.widgetOutput.canvas.axis1.grid() self.widgetOutput.canvas.draw() self.show_fft(filtered,self.widgetFFTAbsFiltered,\ self.widgetFFTLogFiltered)

Then define show_filtering() function to apply filtering based on what user choose in cbFiltering widget as follows:

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def show_filtering(self): strCB = self.cbFiltering.currentText() if strCB == 'Butterworth Highpass': self.butter_filter('hp') if strCB == 'Butterworth Lowpass': self.butter_filter('lp')

Connect currentIndex signal in cbFiltering  widget to show_filtering() function inside def __init__(self) method. This signal is sent whenever the currentIndex in the combobox changes through user:

self.cbFiltering.currentIndexChanged.connect(self.show_filtering)

Run main_fft2.py. Select one of signals and choose Noise radio button. Then, choose one filter from cbFiltering widget. The result is shown in figures below.

The following is full source code of main_fft2.py sow far:

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#main_fft2.py from PyQt5.QtWidgets import * from PyQt5.uic import loadUi from matplotlib.backends.backend_qt5agg import (NavigationToolbar2QT as NavigationToolbar) import numpy as np from scipy import signal from numpy import * import matplotlib as mpl from scipy.signal import chirp class DemoGUIFFT(QMainWindow): def __init__(self): QMainWindow.__init__(self) loadUi("gui_fft.ui",self) self.setWindowTitle("GUI Demo for FFT") self.pbShow.clicked.connect(self.show_graph) self.addToolBar(NavigationToolbar(self.widgetSignal.canvas, self)) self.rbChirp.toggled.connect(self.show_chirp) self.rbSawtooth.toggled.connect(self.show_sawtooth) self.rbSquare.toggled.connect(self.show_square) self.rbSweepPoly.toggled.connect(self.show_sweep_poly) self.cbFiltering.currentIndexChanged.connect(self.show_filtering) def show_graph(self): global y wc = float(self.leCutOff.text()) N = int(self.leFFTLength.text()) M = int(self.leSignalRange.text()) wc = wc*pi # widgetSignal n = arange(-M, M) h = wc/pi * sinc(wc*(n)/pi) mpl.style.use('seaborn') # Noise if self.rbNoise.isChecked(): y = y + np.random.randn(len(h)) * 0.1 else: y = h self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.stem(n,y,\ basefmt='r-',use_line_collection=True) self.widgetSignal.canvas.axis1.annotate('$n$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', xycoords='axes fraction', \ textcoords='offset points', fontsize=20) self.widgetSignal.canvas.axis1.set_title('Stem Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y def show_fft(self, h, qwidget1, qwidget2): wc = float(self.leCutOff.text()) N = int(self.leFFTLength.text()) M = int(self.leSignalRange.text()) wc = wc*pi # widgetFFTAbs w,Hh = signal.freqz(h,1,whole=True, worN=N) # get entire frequency domain wx = fft.fftfreq(len(w)) # shift to center for plotting qwidget1.canvas.axis1.clear() qwidget1.canvas.axis1.plot(w-pi,abs(fft.fftshift(Hh)),\ color='red', linewidth=3.0) qwidget1.canvas.axis1.axis(xmax=pi/2,xmin=-pi/2) qwidget1.canvas.axis1.vlines(\ [-1.1,1.1],0,1.2,color='g',lw=2.,linestyle='--',) qwidget1.canvas.axis1.hlines(1,-pi,pi,color='g',lw=2.,linestyle='--',) qwidget1.canvas.axis1.annotate(r'$\omega$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=22) qwidget1.canvas.axis1.set_ylabel(r"$|H(\omega)| $",fontsize=22) qwidget1.canvas.axis1.set_title('Absolute FFT Graph') qwidget1.canvas.axis1.set_facecolor('lightblue') qwidget1.canvas.axis1.grid() qwidget1.canvas.draw() # widgetFFTLog w,Hh = signal.freqz(h,1,whole=True, worN=N) # get entire frequency domain wx = fft.fftfreq(len(w)) # shift to center for plotting qwidget2.canvas.axis1.clear() qwidget2.canvas.axis1.plot(w-pi,\ 20*log10(abs(fft.fftshift(Hh))),color='red', linewidth=3.0) qwidget2.canvas.axis1.axis(ymin=-40,xmax=pi/2,xmin=-pi/2) qwidget2.canvas.axis1.vlines([-wc,wc],\ 10,-40,color='g',lw=2.,linestyle='--',) qwidget2.canvas.axis1.hlines(0,-pi,pi,color='g',lw=2.,linestyle='--',) qwidget2.canvas.axis1.annotate(r'$\omega$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=22) qwidget2.canvas.axis1.set_ylabel(r"$20\log_{10}|H(\omega)| $",fontsize=18) qwidget2.canvas.axis1.set_title('Log Absolute FFT Graph') qwidget2.canvas.axis1.set_facecolor('lightblue') qwidget2.canvas.axis1.grid() qwidget2.canvas.draw() def show_chirp(self): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) f_start = float(self.leFStart.text()) f_end = float(self.leFEnd.text()) # widgetSignal t = linspace(x_start, x_end, 5001) w = chirp(t, f0=f_start, f1=f_end, t1=10, method='linear') # Noise if self.rbNoise.isChecked(): y = w + np.random.randn(len(w)) * 0.1 else: y = w self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.plot(t,y,linewidth=3.0) self.widgetSignal.canvas.axis1.annotate('$sec$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', xycoords='axes fraction', \ textcoords='offset points', fontsize=20) self.widgetSignal.canvas.axis1.set_title('Chirp Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y def show_sawtooth(self): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) # widgetSignal t = linspace(x_start, x_end, 5001) w = signal.sawtooth(2 * np.pi * 5 * t) # Noise if self.rbNoise.isChecked(): y = w + np.random.randn(len(w)) * 0.1 else: y = w self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.plot(t, y,linewidth=3.0) self.widgetSignal.canvas.axis1.annotate('$sec$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', xycoords='axes fraction', \ textcoords='offset points', fontsize=20) self.widgetSignal.canvas.axis1.set_title('Chirp Graph') self.widgetSignal.canvas.axis1.set_title('Sawtooth Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y def show_square(self): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) # widgetSignal t = linspace(x_start, x_end, 500, endpoint=False) w = signal.square(2 * pi * 2 * t) # Noise if self.rbNoise.isChecked(): y = w + np.random.randn(len(w)) * 0.1 else: y = w self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.plot(t, y, linewidth=3.0) self.widgetSignal.canvas.axis1.annotate('$sec$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', \ fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', \ xycoords='axes fraction', textcoords='offset points', \ fontsize=20) self.widgetSignal.canvas.axis1.set_title('Square Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y def show_sweep_poly(self): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) # widgetSignal p = np.poly1d([0.025, -0.36, 1.25, 2.0]) t = np.linspace(x_start, x_end, 5001) y = signal.sweep_poly(t, p) # Noise if self.rbNoise.isChecked(): y = y + np.random.randn(len(y)) * 0.1 else: y = y self.widgetSignal.canvas.axis1.clear() self.widgetSignal.canvas.axis1.plot(t, y, linewidth=3.0) self.widgetSignal.canvas.axis1.annotate('$sec$', xy=(0.98, 0), \ ha='left', va='top', xycoords='axes fraction', \ fontsize=20) self.widgetSignal.canvas.axis1.annotate('$h$', xy=(0, 1), \ xytext=(-15,5), ha='left', va='top', \ xycoords='axes fraction', textcoords='offset points', \ fontsize=20) self.widgetSignal.canvas.axis1.set_title('Sweep Poly Graph') self.widgetSignal.canvas.axis1.set_facecolor('lightblue') self.widgetSignal.canvas.axis1.grid() self.widgetSignal.canvas.draw() self.show_fft(y,self.widgetFFTAbs, self.widgetFFTLog) return y def butter_filter(self, param): global y x_start = float(self.leXStart.text()) x_end = float(self.leXEnd.text()) t = linspace(x_start, x_end, len(y)) pass_band = float(self.lePassBand.text()) stop_band = float(self.leStopBand.text()) #Butterworth filtering sos = signal.butter(stop_band, pass_band, param, fs=1000, output='sos') filtered = signal.sosfilt(sos, y) self.widgetOutput.canvas.axis1.clear() self.widgetOutput.canvas.axis1.plot(t, filtered) self.widgetOutput.canvas.axis1.set_ylabel("$h$",fontsize=22) self.widgetOutput.canvas.axis1.set_xlabel("$sec$",fontsize=22) self.widgetOutput.canvas.axis1.set_title('Butterworth Filtered Signal') self.widgetOutput.canvas.axis1.set_facecolor('lightblue') self.widgetOutput.canvas.axis1.grid() self.widgetOutput.canvas.draw() self.show_fft(filtered,self.widgetFFTAbsFiltered, \ self.widgetFFTLogFiltered) def show_filtering(self): strCB = self.cbFiltering.currentText() if strCB == 'Butterworth Highpass': self.butter_filter('hp') if strCB == 'Butterworth Lowpass': self.butter_filter('lp') if __name__ == '__main__': import sys app = QApplication(sys.argv) ex = DemoGUIFFT() ex.show() sys.exit(app.exec_())

Signal Processing with Python GUI: Part 4