Using Simulink

Model Definition

   1.

Select New from the Simulink File menu. A new block diagram window appears on your screen.

   2.

Double-click on the Sources, Sinks, and Discrete icons in the Simulink window. The Sources, Sinks, and Discrete libraries appear on your screen.

Alternatively, you can view the libraries' contents by clicking the  symbol in the Library Browser to expand the hierarchical list.

   3.

Drag the Signal Generator block from the Sources library into the new block diagram window.

   4.

Drag the Discrete Filter block from the Discrete library into the new block diagram window.

   5.

Drag the Scope block from the Sinks library into the new block diagram window.

   6.

Connect the blocks.

Position the cursor near the output port of the Signal Generator block. Hold down the mouse button (the left button for a multibutton mouse) and drag the line that appears until it touches the input port of the Discrete Filter block. Using the same technique, connect the output of the Discrete Filter block to the input port of the Scope block. Your model looks like this:

   7.

Set the block parameters:

1. Double-click on the Signal Generator block. A window appears that lets you set the block's parameters. Parameters are defining values that tell the block how to operate. For this example, select sine from the Wave form pop-up menu. Set the Frequency to 2.5 by typing in the text field.

   

Close the window by clicking on the OK button or by pressing Enter on the keyboard.

1. Double-click on the Discrete Filter block. Set the Denominator field to [1 -0.9], or enter the name of a MATLAB workspace variable that contains this vector. Set the Sample time parameter to 0.01. Close the dialog box by clicking on the OK button or by pressing Enter on the keyboard.
2. Double-click on the Scope block. Right-click on the vertical axis and select Axis properties from the pop-up menu. Set Y max to 7 and Y min to -7. Click OK.

   8.

In the model window, select Parameters from the Simulation menu. Set Stop time to 4 and click OK.

Model Simulation

   1.

Double-click on the Scope block if the Scope window is not already open on your screen. A scope window appears.

   2.

Select Start from the Simulation menu for the block diagram window.

When you select Start, the simulation progresses according to an underlying integration routine for continuous blocks, or a sample rate for discrete blocks. For this model, and for most models constructed with the DSP Blockset, the blocks process their inputs at a discrete sample interval.

   3.

Experiment with the block parameters. To change block parameters during the simulation:

1. Select Parameters from the Simulation menu and change the Stop time to inf. The inf setting instructs Simulink to run the model for as long as the computer's memory allows.
2. Double-click on the Signal Generator block to open it.
3. Select Start from the Simulation menu to start the simulation.
4. Change the frequency of the sine wave in the Signal Generator block. Try typing 1, 0.1, and 0.01 in the Frequency field, pressing Apply after entering each new value. Observe the changes on the scope.

Many blocks have parameters that you cannot change while a simulation is running. There are some parameters, however, that you can tune without terminating the simulation. In Chapter 4, "DSP Block Reference," these parameters are designated by a icon, indicating that they are tunable while the simulation runs.

   4.

Select Stop from the Simulation menu to stop the simulation.