Development and Implementation of GUI using MATLABof GUI using MATLAB

for Fast Fourier Transformation

Presented by:

Binayak Ojha

Date: 09.05.2013

1. Motivation2. Objectives3. Discrete Fourier Transform (DFT)4. Fast Fourier Transform (FFT)5. Windowing5. Windowing

5.1 Rectangular Window5.2 Hamming Window5.3 Hanning Window

6. Some MATLAB Functions7. GUI-control Elements8. GUI-control Elements Properties9. GUIDE

9.1 Layout Editor9.2 Property Inspector9.3 Object Browser9.4 Menu Editor

10. GUI Layout Design10. GUI Layout Design11. Algorithm for designed GUI12. Use of CallBack Function13. MATLAB code for FFT14. Output Snapshots15. ConclusionReferences

•Need of some simulations for demonstration.

•To develop and implement GUI for FFT

Other requirements1.Two separte plots for input and output signal.2.Cosine signal as input signal.2.Cosine signal as input signal.3.Frequency spectrum of FFT of input as output.4.Demonstration of leakage effect.5.Windowing demonstration6.Sliders to change input and output signal characteristics.

• A signal can be collection of frequency components.•Extracts the signal component F(ω) at frequency ωMathematically represented as,

f[k] : discrete signalN: Number of samples

•Algorithm to calculate DFT fast and efficiently. •First published in 1965 by Cooley and Tuckey.•Applies only to signals with elements 2m.•FFT returns set of complex numbers.•But, real numbers for f=0 and f= fs /2.•But, real numbers for f=0 and f= fs /2.

•Output spectrum of DFT has spectral leakage.•Windowing minimize spectal leakage.•DFT of x[i]×w[i] is done. •Different types of window functions available.1.Rectangular Window2.Hanning Window1.Rectangular Window2.Hanning Window3.Hamming Window

W[n] = 1 for n ≤ N= 0 for n > N

^

Figure 1 : Cosine Signal in Rectangular Window

W[n] = 0.5- 0.5 cos for n ≤ N= 0 for n > N

Figure 2: Cosine Signal in Hanning Window

W[n] = 0.53836 - 0.46164 cos for n ≤ N= 0 for n > N

Figure 3: Cosine Signal in Hamming Window

Y = fft(x)returns the DFT of vector x, “[2]”.

w = hamming(L)returns an L-point symmetric Hamming window in returns an L-point symmetric Hamming window in the column vector w, “[2]”.

w = hann(L) returns an L-point symmetric Hann window in the column vector w, “[2]”.

Table 1: MATLAB GUI-Control Elements “[4]”

S.N UI Control Style Value Description

1 Check Box ‘checkbox’ Indicates the states of an option

2 Editable Text ‘edit’ User editable text box

3 Frame ‘frame’ Usedto groupthecontrols3 Frame ‘frame’ Usedto groupthecontrols

4 Pop-up Menu ‘popup’ Provides the list of options

5 List Box ‘listbox’ Shows scrollable list of options

6 Push Button ‘pushbutton’ Invokes an event immediately

7 Radio Button ‘radio’ Indicates selectable options

8 Toggle Button ‘toggle’ Two states, “ON” or “OFF”

9 Slider ‘slider’ Represents a range of values

10 Static Text ‘text’ Displays a string in a box

Table 2a:GUI-Control Elements Properties “[4]”

S.N. Property S.N. Property

1 BackgroundColor 8 FontName

2 ButtonDownFcn 9 FontSize

3 CData 10 FontUnits3 CData 10 FontUnits

4 CallBack 11 FontWeight

5 Enable 12 ForegroundColor

6 Extent 13 HorizontalAlignment

7 FontAngle 14 Interruptible

Table 2b: GUI-Control Elements Properties “[4]”

S.N. Property S.N. Property

15 ListBoxTop 22 TooltipString

16 Max 23 Units

17 Min 24 UIContextMenu17 Min 24 UIContextMenu

18 Position 25 Value

19 String 26 Tag

20 Style 27 UserData

21 SliderStep 28 Visible

•Stands for GUI Development Enviornment•MATLAB tool to create GUI•Easy to use

Components of GUIDE1.Layout EditorComponents of GUIDE1.Layout Editor2.Property Inspector3.Object Browser4.Menu Editor

Figure 4: GUIDE Layout Editor

Figure 5: GUIDE Property Inspector

Figure 6: GUIDE Object Browser

Figure 7: GUIDE Menu Editor

Figure 8: GUI Layout

Step 1: StartStep 2: Set the value of slider 1, slider 2, slider 3

and slider 4 to zero.Step 3: Reset Hanning and Hamming Window.Step 4: Compute FFT length using slider 4 value and

show in edit text box 4.Step 4: Compute FFT length using slider 4 value and

show in edit text box 4.Step 5: Set the rectangular window.Step 6: Show slider 1, slider 2, and slider 3 values in

edit text box 1, edit text box 2 and edit text box 3 respectively.

Step 7: Compute FFT length using slider 4 value and show in edit text box 4.

Step 8: Compute input signal array for currently active window and current sliders values.

Step 9: Compute FFT and output signal array.Step 10: Plot input signal in axes 1 and output signal

in axes 2.Step 11: If slider 1 or slider 2 or slider 3 or slider 4

in axes 2.Step 11: If slider 1 or slider 2 or slider 3 or slider 4

has new value then go to step 4.Step 12: If edit text box 1 or edit text box or edit text

box 3 or edit text box 4 have new value, set the value of respective slider. Go to step 6.

Step 13: If Hanning window is set, reset the hamming window and rectangular window.

Go to step 8.Step 14: If Hamming window is set, reset the

hanning window and rectangular window. Goto step 8.

Step 15: If hanning and hamming both are reset, compute rectangular window vector.

Step 15: If hanning and hamming both are reset, compute rectangular window vector. Goto step 8.

Step 16: Stop

•An important property of a GUI Element•Indicates actions to be performed when activated

function slider1_Callback(hObject, eventdata, handles)

set(handles.edit3,'string',(int32(get(handles.slider1,'value'))));

Figure 9: Implementation of Callback Function

set(handles.edit3,'string',(int32(get(handles.slider1,'value'))));

my_task(get(handles.slider1,'value'),get(handles.slider3,'value'),get(ha

ndles.slider6,'value'),get(handles.slider7,'value'));

k=fft_length(s3) ; % function fft_length() returns number of fft points

if k >1

fftval=fft(x,k); % calculate array of fft for k points

indexnyquist=(k/2)+1; %centre FFT point

fftval=fftval(1:indexnyquist); %truncate the negative parts

k=cast(k,'double');

Figure 10: Implementation of FFT

k=cast(k,'double');

fftval=fftval/k; %scale

%whos k

fftval(2:end)=2*fftval(2:end); %compensate for truncating

df=fs/k ; %discrete frequency interval

frequency_axis=(0:indexnyquist-1)*df; %array of frequency to plot

magnitude=abs(fftval); % magnitude of spectrum

plot_output(frequency_axis,magnitude); % plot the fft in frequency spectrum

Figure 11: Output snapshot 1

Figure 12: Output snapshot 2

•GUIDE is a good tool for GUI designing. •GUI for FFT was developed and implemented.•GUI for other complex processes can be developed.

1.www.mathworks.de/academia/student_center/tutorials2.www.mathworks.com3.Discrete Time Signal Processing, Second Edition, Allan V Oppenheim4.Graphics and GUIs with MATLAB, Third Edition, Patrick Marchand & O. Thomas HollandMarchand & O. Thomas Holland