This module accompanies the Connexions tutorial given at ICASSP 2008. This is part of the IEEE-SPS initiative to develop IEEE-reviewed signal processing educational materials in Connexions. Remember that content published in Connexions is not automatically reviewed by the IEEE. If you would like to have a module reviewed, once you have published it, fill out an IEEE Content Submission Form.You will find here:Copy of PowerPoint slide presentation PDF of slide presentation PDF of speaker notes for hands-on part of tutorial The tutorial practice module text The tutorial practice module figure The tutorial practice module links The tutorial practice module exercise Suggestions for importing your own materials during the tutorial Notes on LaTeX import Post-tutorial Help suggestions.

Importing a Word Document The tutorial followed the steps for importing a Word document and editing it in Connexions. Although at this point you will want to begin working with your own materials, the materials for the practice module are still below, in case you would like to refer to them. The most important thing to remember when taking this route is that regular Word styles, including some headings, will not import properly. Create your Word document using the Connexions document template. Save the template on your computer as a .dot document, that is, as a template rather than an ordinary document; then choose the template whenever you begin a new document that you will be importing to Connexions. Click on the heading to type the heading of your first section, then replace all of the "how-to" text in the template with your text. Use the Connexions styles (under styles, in the Format drop-down box) to create more headings, as well as terms, emphasis, and other styles that will import into Connexions. If your version of Word makes using the template difficult, you can always save the template as a regular Word document. To create a Connexions-ready text, open the Word template document and replace all the text with your text. Word will then let you select Connexions styles for terms, headings, etc., in this document, which will import smoothly to Connexions. Remember that importing plain text (or typing text directly into Connexions), and adding text styles and headings while editing in Connexions, is also an option. If your module contains many equations or tables, you may prefer to import a LaTeX file. Remember, you can only import one text document. Any subsequent imports will replace, rather than add to, what is already in the module. If the figures do not import properly when embedded in the Word document, you can import them one at a time, as many as you like, using the Import box under the Files tab of your module, and place them wherever you like by "adding" the figure in edit-in-place.

LaTeX Import If your lesson is already a LaTeX document, or if it contains many equations or tables, you will find importing a LaTeX document to be your easiest route. Tables should convert directly, and equations should convert to MAthML automatically. Also, Connexions retains the size specifications for eps files in LaTeX and uses them when generating PDF files.Here is the Connexions-compatible LaTeX Template. For more instructions on importing LaTex files, see Using LaTeX to Create Connexions Modules. Here is a .zip file that contains an Example Module in LaTeX and an associated .eps figure.

Practice Module Here are the text, figure, links, and exercise used in the practice module in the tutorial.

Text for Practice Module First download the Connexions Word Template and open a new document using the template. Click on "Section Name" to type in the section name (Discrete-Time Fourier Transform). Delete all the "How to Use the Template" instructions, and replace them with your text. To use our practice module text, you can simply copy the text from and paste it into your new document. Or open this example text, and copy and paste from it. If you do not have Word or cannot download the template, but still wish to use our practice text to follow the rest of the tutorial, here is a Connexions-ready version of the text. The Discrete-Time Fourier Transform (DTFT) is the primary theoretical tool for understanding the frequency content of a discrete-time (sampled) signal. The DTFT is defined as The inverse DTFT (IDTFT) is defined by an integral formula, because it operates on a continuous-frequency DTFT spectrum: The DTFT is very useful for theory and analysis, but is not practical for numerically computing a spectrum digitally, because For practical computation of the frequency content of real-world signals, the Discrete Fourier Transform (DFT) is used. The DFT gives the discrete-time Fourier series coefficients of a periodic sequence of period N samples, as can easily be confirmed by computing the inverse DTFT of the corresponding line spectrum. The DFT can thus be used to exactly compute the relative values of the N line spectral components of the DTFT of any periodic discrete-time sequence with an integer-length period. In most cases, the signal is neither exactly periodic nor truly of finite length; in such cases, the DFT of a finite block of N consecutive discrete-time samples does not exactly equal samples of the DTFT at specific frequencies. Instead, the DFT gives frequency samples of a windowed (truncated) DTFT.

Figure for Practice Module Here is the example figure. Save it as "stemplot.png" on your computer, and remember where you saved it.

Links for Practice Module To quickly add a link to your module, copy and paste one of the following: To add A link to a different module: See DTFT ]]> . A link within your module: See DFT ]]> . A link to a specific element in a different module: See Nyquist Frequency ]]> . An "empty" link to an element that Connexions will name: See ]]> . Change the target to the id of a figure in your module! A link outside Connexions: See Kaiser window ]]> .

Exercise for Practice ModuleYou can include whatever elements you want - paragraphs, figures, tables, lists, etc. - in both the problem and the solution of an exercise. Anything in the "solution" will be hidden until the student wants to see it, as in Problem . If you'd like to include this exercise in your practice module, in Edit-in-Place, choose "Exercise...Add Here", where you would like the exercise to appear. Then in the exercise editing box, copy and paste the text, for both the problem and the solution, into the appropriate paragraphs: For what class of signals are the DFT samples exactly equal to samples of the DTFT? For signals that are non-zero only over the sample range n = 0,1,...,N-1. Now that you've created the module, you can go back and change it completely; replace the practice elements with your own text, figures, exercises, etc., to create something that you'd like to publish.

Post-Tutorial Help Don't forget that there are plenty of links to help from the Help tab at the top of your Connexions page, including links to a Quick Start page and a New Author Guide. The CNXML Stress Test is a demo module using all the tags presently available; you may find it useful as a reference guide to what can be done. Basic CNXML is the first of a set of modules that give detailed instructions for every tag possible in Connexions. To look up more advanced tags, you may have to search Intermediate CNXML or Advanced CNXML.