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The Design Cycle
If this doesn’t work, make sure the bin directory of the JDK installation
is on the Path in your command shell. Alternately, you can change
directories to the JDK bin directory and run the above command from there.
LWDFDesigner does not require any command line arguments.
LWDFDesigner is written as a graphical-based wizard that guides you
through the steps necessary to successfully design a filter. Each wizard page or
panel validates the user entered data before allowing the user to proceed to
the next page/panel. As you enter data into the program, you should tab
between fields to commit and validate data. When the program is satisfied with
the entered data, the ‘Next’ button will be enabled allowing you to move to the
next page. The screenshots shown give you an idea of what to expect.
I would like to tell you that by
using a LWDF design tool you are
able to crank out filters that match
your specifications exactly every
time, but I cannot. I know from
implementing LWDFDesigner that
inside these design programs are
approximations and parameter
quantizations that result in a filter that,
in most cases, is close to what
was specified. In fact, both the
TI program and LWDFDesigner
support the concept of design margin
which has direct impact on the
Design margin is a number from 0
.. 1 which determines whether the filter’s stopband or the passband should
be given the most effort to get right.
Values towards one concentrate the
design accuracy on the passband.
Values towards zero concentrate on
the stopband. Tweaking the design
margin just a little bit changes the
generated gamma values; sometimes
by quite a bit.
With these facts in mind, the
LWDF design cycle looks something
You may find the following
• Java version 5 is available at:
• A Texas Instruments application
note discussing Lattice Wave
Digital Filters is available at:
• Fettweis, Alfred, “Wave Digital
Filters: Theory and Practice”,
Proceedings of the IEEE, Vol. 74,
pp. 276-327, February 1986.
• Gazsi, Lajos, “Explicit Formulas
for Lattice Wave Digital Filters”,
IEEE Transactions on Circuits and
Systems, Vol. 32, No. 1, pp. 68-88,