lab3_revised - Spring 2011 Clark EE 341 Lab 3: The DFT and...

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Spring 2011 Clark EE 341 Lab 3: The DFT and Digital Filtering Due: In your discussion section May 11-13 When using a digital computer, frequency analysis and filtering requires that we use the Discrete Fourier Transform (DFT). In this lab we spend some time becoming familiar with using the Fast Fourier Transform (FFT) implementation of the DFT to study the frequency content of a discrete-time signal. 1. MATLAB function FFT In this problem you will learn how to use the MATLAB command fft . First, use the help feature in MATLAB to learn the syntax of the fft function. The FFT function computes the Discrete Fourier Transform (DFT) of a sequence. In general the FFT of a sequence will be a complex function so you will need to look at the magnitude and phase separately. The MATLAB commands abs and angle are useful for obtaining the magnitude and phase of a complex valued sequence. Also, since the FFT only has values at discrete frequencies, it may be useful to do the plots with stem to reinforce that idea, but continuous frequency plots (i.e. using plot ) are often used since they approximate the DTFT that you are ultimately interested in. You may use either one for your report. The FFT outputs a sequence over the frequency range 02 . You are probably more familiar with seeing the spectrum plotted over the range   (or normalized 11 f   ). The fftshift function can be used for this purpose.
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lab3_revised - Spring 2011 Clark EE 341 Lab 3: The DFT and...

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