Hopefully, a person could start using the MATLAB convolution tool without any need to
read these help files. Features were designed to be intuitive and familiar to those
with basic computer experience. If not send me mail by clicking on my name in the Overview section!!
For those who like to read the manual (don't be ashamed, I am one of these people),
this section will give you the minimum you need to get started and be comfortable with the
use of the GUI.
First, if you have not already done so, follow the information given in the Installation section to install and start the MATLAB convolution tool.
To begin, pick an input signal and an impulse response:
- Press the Get x(t) button in the main window. A second window
should open with a pulse signal displayed. If you wish, alter the signal type using
the list box at the top of the window, and alter the signal parameters with the controls along
the right side. Note that time parameters for the sine and
cosine (length, period,
delay) must be specified in seconds.  When satisfied click the
OK button. The signal you picked is now displayed within the
Input plot box.
Note: The signal may not be fully displayed when changing the signal
parameters. To replot the signal, click inside the plot box.
- Make sure the Flip h(t) radio button is checked and then pick an
impulse response by pressing the Get h(t) button. After choosing
an impulse response and closing the window, the three large axes will now contain the
following information:
- The top axis displays the Input signal
in blue and flipped version of the Impulse Response
in red.
- The middle axis shows the multiplication of the Input
signal and Impulse Response at that particular instance of
time. (This may initially be empty.)
- The bottom axis shows the output of the linear convolution between the Input signal and the Impulse
Response signal.
- There are two labels with arrows pointing to the current time. One is below the
Signal / Flipped Signal plot box. The other is above the
Output plot box. Move the mouse over either of these. The mouse
pointer should become a hand symbol indicating that the current time can be changed by dragging
the t time label.
Go ahead and drag the time label around to change the value of the current index
location. Quite a few things happen: The Flipped Impulse
Response follows the location of the time location, and the
multiplication plot changes depending on the relative overlap between the
Input signal and the Flipped
Impulse Response.
- Change the time so that the two signals overlap in the Signal / Flipped
Signal window. There will now be a nonzero plot within the
multiplication axis.
Note that the current time is highlighted in the Output plot. The
numeric value (i.e., the value on the y axis) of this time is determined by integrating the
area within the multiplication plot.
Ex. If the signals overlapped so that the multiplication plot
integrated to a value of 6, the highlighted value in the output plot would
have a value of 6.
That's it! You now understand the basics of how to use the MATLAB convolution
tool. For a more in depth description of convolution theory and how a convolution is
calculated see the Theory section. The Controls and Menus
sections provide a description of all the elements in the user interface.