Re: Design of FIR filter with Sharp Transition and High Stop Band Attenuation

gaurav811 wrote: 
Ok.. This was my first posting in DSP guru so I am sorry for being a little
sloppy. Here are the specs. The filtered signal is sampled at 19.0699MHz.
It needs to be filtered by a half band filter. The filter must have cutoff
at 9.53495 MHz. Its a digital filter and yes I do know that with FIR`s I
should not expect much steep a transition. But I want to get as steep as I
can get since the signal is actually a sampled Luminance singnal from a
camera CCD. Hence any attenuation all attenuation below the nyquist rate
will cause contrast problems. Well so here are the design specs

I need 60Db attenuation at the nyquist rate i.e at 9.53495Mhz. Hence I
will need to move my cutoff to below 9.534...Mhz but closer to it the
better i.e narrower the transition widthe the better.

Ofcourse I want ripple free pass band too. So having so ideal requirements
can you suggest I can get ?

As Jerry said " Engineering is the art of making what you want from things
you can get." ......my question is what is the best that is available.

thanks
Gaurav
gaurav811 wrote:
Hi 

I have to design a FIR filter with very steep transition at cutoff and
high stop ban attenuation. FIR bcoz I need linear phase. I have matlab
available. Fdatool is useless since its FIR dont have a good
transition.
In literature search I came by papers talking about Sharp transition
FIR`s
using Frequency response masking and multirate filters. I wanted to
know if 
someone has any experience with these filters ? I am going to try to
implement these and wanted to know what issues/problems I can face and
are
these papers claims any good.

If you also know of some technique for implementing sharp transition
FIR`s
with low number of coeff`s let me know. Also if you know some
material/book 
that might help me with this point it to me.

thanks in advance. Any information relavent or irrelavant is welcome.
How sharp is sharp? What attenuation do you call high? The "better" the filter, the more coefficients it will have. There are some phenomena you

can use to advantage, such as the alternating zeros in half-band filters, that can reduce the number in special circumstances. Without better specs, no specific suggestion is possible.

Jerry
--
Engineering is the art of making what you want from things you can get.
¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯



MAXFLAT filters are ripple free. Halfband MAXFLATs have maximal flatness at ends of the frequency band (zero and fs/2, where fs is the sampling frequency). If you move these points of flatness from the ends of the frequency band to inside, transition band will get narrow but performance will slightly deteriorate at the ends. You can experiment with different points, but I think middle of pass and stop bands could be good choice.

Ishtiaq.
.

Relevant Pages

  • Re: Latest Swift data rules out beamed theory
    ... This is a circular argument we are having vis a vis Tarot. ... one or all of the bvri filter. ... It claims an R band detection and r band is in optical. ... very deep upper limits. ...
    (sci.astro)
  • Re: LightSquared Flunks GPS Interference Tests: What Now?
    ... outside their allocated band. ... passing a much weaker signal to the GPS receiver. ... Guard bands, filter shape ... power doubles when the transmitter power is quadrupled. ...
    (sci.geo.satellite-nav)
  • Re: Regarding comparison of audio quality
    ... the more the filter length I use more is the error that is showing up. ... put an integer delay in each output band ... For reasonable QMF filter choices, ... will be aliasing within each analysis frequency band. ...
    (comp.dsp)
  • Re: QMF banks in G.722
    ... I will do further study on filter bank. ... I find QMF banks in G.722 are not perfect reconstruction. ... of the low band from the high band, and vice versa, you need a perfect ... Out of curiosity I just turned off the ADPCM sections of my own G.722 ...
    (comp.dsp)
  • Re: Sr. Citizen Question Re IF BW Settings
    ... Then there is the bandwidth of the filter. ... The same principal applies to SSB (single side band), ... Hams and commerical radio operators before WWII were trained to copy with wide ... Stronger signals can be received with less gain, ...
    (rec.radio.shortwave)