0.3 Lab 3 - frequency analysis  (Page 2/4)

Getting started with simulink

In this section, we will learn the basics of Simulink and build a simple system.

For help on "Simulink" click here . For the following sections download the file Lab3Utilities.zip .

To get the library of Simulink functions for this laboratory, download the file Lab3Utilities.zip . Once Matlab is started, type “Lab3” to bring up the libraryof Simulink components shown in [link] . This library contains a full library of Simulink blocks,a spectrum analyzer and network analyzer designed for this laboratory, a sine wave generator, a scope,and pre-design systems for each of the experiments that you will be running.

In order to familiarize yourself with Simulink, you will first build the system shown in [link] . This system consists of a sine wave generatorthat feeds a scope and a spectrum analyzer.

1. Open a window for a new system by using the New option from the File pull-down menu, and select Model .
2. Drag the Sine Wave , Scope , and Spectrum Analyzer blocks from the Lab3 window into the new window you created.
3. Now you need to connect these three blocks. With the left mouse button, click on the output of the Sine Wave and drag it to the input of the Scope . Now use the right button to click on the line you just created, and dragto the input of the Spectrum Analyzer block. Your system should now look like [link] .
4. Double click on the Scope block to make the plotting window for the scope appear.
5. Set the simulation parameters by selecting Configuration Parameters from the Simulation pull-down menu. Under the Solver tab, set the Stop time to 50, and the Max step size to 0.02. Then select OK . This will allow the Spectrum Analyzer to make a more accurate calculation.
6. Start the simulation by using the Start option from the Simulation pull-down menu. A standard Matlab figure window will pop up showingthe output of the Spectrum Analyzer .
7. Change the frequency of the sine wave to 5*pi rad/sec by double clicking on the Sine Wave icon and changing the number in the Frequency field. Restart the simulation. Observe the change in the waveform andits spectral density. If you want to change the time scaling in the plot generated by the spectrum analyzer, from the Matlab prompt use the subplot(2,1,1) and axis() commands.
8. When you are done, close the system window you created by using the Close option from the File pull-down menu.

Continuous-time frequency analysis

For help on the following topics select the corresponding link: simulink or printing figures in Simulink .

In this section, we will study the use and properties of the continuous-time Fourier transform with Simulink.The Simulink package is especially useful for continuous-time systems because it allows thesimulation of their behavior on a digital computer.

Synthesis of periodic signals

Double click the icon labeled Synthesizer to bring up a model as shown in [link] . This system may be used to synthesize periodic signals byadding together the harmonic components of a Fourier series expansion.Each Sin Wave block can be set to a specific frequency,amplitude and phase. The initial settings of the Sin Wave blocks are set to generate the Fourier series expansion