Re: Filter design pls help

On Mon, 22 Oct 2007 09:32:33 -0700, sunilammanabrolu wrote:

I was given a project to design, simulate and synthesize a digital low
pass filter with cutoff frequency 150 Hz and stop band attenuation of
80 db/decade

The filter i have chosen is iir Butterworth filter with order 4
I have relialized the filter using fdatool in matlab
Can any one pls help me with the vhdl code
thx in advance

That's an extremely general request, in that there's a whole bunch of steps
to get from a filter definition to a working implementation on an FPGA or
ASIC. You really need to tell us what step isn't working for you.

In the absence of other information, I would suggest that you start by
writing VHDL that implements the filter in simulation, but without trying
to make it synthesizable. If you're really at a loss you may want to
start by getting the algorithm to work in a spread***, MATLAB, C, or
whatever other language you are most comfortable in, then move to VHDL.

At any rate, once you get the algorithm working in VHDL in simulation,
then you should be able to rewrite it as something that's sythesizeable,
and start debugging (and yes, you will be doing some debugging).

If you're having trouble with the first step, i.e. going from the z-domain
filter to an algorithm, look about 3/4 of the way down in
http://www.wescottdesign.com/articles/zTransform/z-transforms.html or in a
good reference on practical DSP such as Rick Lyons' "Understanding Digital
Signal Processing", in Chapter 6 where he talks about IIR filters.

Good luck, and check back here when you figure out just where it is in the
process that you're getting stuck.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
.