ECET 357 Real-Time Digital Signal Processing

Sampling, A/D, and D/A

January 18, 2007

Lecture Note 2

MATLAB Simulink Example

Step 1. Start MATLAB

Step 2. Start Simulink

To start Simulink, you type simulink at the command window

>> simulink

Step 3. Creating a Simulink Model File:

Click on File → New → Model

• Display a Simulink Model Editing Screen
• File →Save As (create a new folder and give a file name, for example: Sine_Signal_1.mdl)

Step 4. Select any needed function blocks, one at a time, on the Simulink Library Browser, and Drag them into the Simulink Model editor screen

For example,

• Click on Sources, select and drag Sine Wave block into the Simulink model editor
• Click on Sinks, select and drag Scope block into Simulink model editor
• Use your mouse to connect the output of the Sine Wave block to the input of the Scope

Step 5. Setup signal parameters for Sine Wave

• Double click the Sine Wave block to change the amplitude, frequency (rad/sec), sampling time etc
• In this example, we have 5v, 60 Hz
• Then click on OK to close the parameter window

Step 6. Setup Simulation Parameter

• Click on Simulation menu located on the Simulink model editor
• Simulation → Configuration Parameters; and then give the following parameters
• Simulation time: start time 0.0, Stop time 0.1 sec
• Solver option: Fixed type

Step 7. Start Simulation and View the Scope output

• Double click on Scope block located on the model editor
• Click on Simulation → Start

Step 8. Refine Parameters and More Testing

8.1 Change Fixed-step size: 0.01

8.2

• Add a To Workspace block to the Simulink editor
• Connect it to the Sine Wave

· Double click To Workspace block, and specify a variable name “sine60”

· Start simulation to see the Scope output

· Then go to MATLAB Command window, and type “whos” command to see variables

>> whos

Name Size Bytes Class

ans 901x1 271880 cell array

sine60 11x1 88 double array

tout 11x1 88 double array

· Then type plot(sine60), and stem(60) to see the MATLAB plots

>> plot(sine60)

>> stem(sine60)

8.3 Calculate the sampling time: Nyquist Sampling Rate

• Fs = 2 * f = 120Hz
• Ts = 1/Fs = 0.083 sec
• Then change Fixed-step size: 0.083

>> whos

Name Size Bytes Class

ans 901x1 271880 cell array

sine60 2x1 16 double array

tout 2x1 16 double array

· Then type plot(sine60), and stem(60) to see the MATLAB plots

>> plot(tout,sine60), grid on

>> stem(tout,sine60), grid on

8.4 Change the Fix-step size to 0.001

• Ts = 0.001, Fs = 1/Ts = 1000 Hz
• Restart the simulation

>> whos

Name Size Bytes Class

ans 901x1 8 double array

sine60 101x1 808 double array

tout 101x1 808 double array

· Then type plot(sine60), and stem(60) to see the MATLAB plots

>> plot(tout,sine60), grid on

>> stem(tout,sine60), grid on

Step 9. Copy Model and Prepare Report

• Edit → Copy Model to Clip board
• Paste on MS Word, Powerpoint slide, etc