Prev: LoadLibrary failed with error 14082
Next: add line w/o changing limits
From: david t53 on 7 Jul 2010 05:38
fdesign has several filter responses to choose from: arbmag, arbmagnphase, audioweighting, bandpass, bandstop...

There is a line description of each filter response here: http://www.mathworks.com/access/helpdesk/help/toolbox/filterdesign/ref/f11-35125.html#f11-36634

and clicking to one of types give help information about how to use the parameters.

is there a documentation (web page, book or something else) somewhere that explains a bit more about each of these type of filter responses, and what is commonly used for?


best regards,
David
From: Rune Allnor on 7 Jul 2010 05:45
On 7 Jul, 11:38, "david t53" <david_...(a)sogetthis.com> wrote:
> fdesign has several filter responses to choose from: arbmag, arbmagnphase, audioweighting, bandpass, bandstop...
>
> There is a line description of each filter response here:http://www.mathworks.com/access/helpdesk/help/toolbox/filterdesign/re...
>
> and clicking to one of types give help information about how to use the parameters.
>
> is there a documentation (web page, book or something else) somewhere that explains a bit more about each of these type of filter responses, and what is commonly used for?

Probably not.

Filters are not devices to be studied in their own right [*],
but rather means to an end. In other words, one does not learn
the proerties of a lot of filters and then find ways to use
them, but rather learns how to design the filter one needs for
the job at hand.

[*] There is, of course, the subject of Digital Signal Processing
that traditionally has covered how to design - and the properties
of - a number of different filter types. I prefer to compare DSP
to the telegraphists of ancient times: It was a specialist's
vocation that required training and skills in handling morse code
far beyond what a layman could possibly be expected to invest.
But as technology evolved, morse code was no longer required,
and users could be trained to handle their own communications
in a matter of hours.

Rune
From: david t53 on 7 Jul 2010 06:00
ps: I am aware that there a many books about filter design,
but I'd like it to be focused on matlab and the Filter Design toolbox.
From: Wayne King on 7 Jul 2010 06:21
"david t53" <david_t53(a)sogetthis.com> wrote in message <i11htt$qfb$1(a)fred.mathworks.com>...
> fdesign has several filter responses to choose from: arbmag, arbmagnphase, audioweighting, bandpass, bandstop...
>
> There is a line description of each filter response here: http://www.mathworks.com/access/helpdesk/help/toolbox/filterdesign/ref/f11-35125.html#f11-36634
>
> and clicking to one of types give help information about how to use the parameters.
>
> is there a documentation (web page, book or something else) somewhere that explains a bit more about each of these type of filter responses, and what is commonly used for?
>
>
> best regards,
> David

Hi David, as Rune has stated, the individual reference pages for the filter specification objects do not give you a lot of detail about the underlying design methods. Typically each of the filter specification objects supports a number of design methods depending on which specification string you use AND whether you have the Filter Design Toolbox in addition to the Signal Processing Toolbox. In all cases, there is a default filter design method used when you call fdesign in conjunction with design.

Depending on your use case, you may or may not have to know a lot about the theory behind the design methods. However, you might want to acquaint yourself with some of the basic differences between IIR filters and FIR filters--the advantages and disadvantages of each. The IIR-FIR distinction is a common user choice in the fdesign-design paradigm. As a quick example. Suppose you want to design a lowpass filter for data sampled at 1 kHz. You want your filter to pass everything below 100 Hz, and stop everything above 120 Hz (between 100 and 120 Hz is a transition region). You want only 0.5 dB of ripple in the passband, and 60 dB of attenuation in the stopband. You would create a lowpass filter specification object with:

H = fdesign.lowpass('Fp,Fst,Ap,Ast', 100,120,0.5,60,1000);

If you enter:

designmethods(H)

You will see all the filter design methods available to you for that particular filter specification.

You can design the filters with:
% FIR equiripple
De = design(H,'equiripple');
% IIR Butterworth
Db = design(H,'butter');
% Compare their magnitude responses
fvtool([De Db])

You can also query a number of other things about your filter designs to decide which one works best for you.

Wayne
From: david t53 on 7 Jul 2010 06:47
Thanks for the answers.

I am looking for some insights, such as:

what is the purpose of a fdesign.parameq when there is already a fdesign.bandpass and a fdesign.bandstop? that is, what is the difference on using the parameq instead of one of the other two?

or, some more explanation about fdesign.interpolator, and its relation to all the other filter responses?
 |  Next  |  Last
Pages: 1 2 3
Prev: LoadLibrary failed with error 14082
Next: add line w/o changing limits