How to design an IIR filter using slope(db/oct) information

Topic : To design an IIR HPF filter using IPP(Intel Integrated Performance
Primitives) library.
Current need: to calculate BW or Q from slope.

The specification of filter is :
Cutt-off frequency : in Hz
Slope : in dB/oct

We are having an IPP library which has IIR filter implementation
function. This function has following parameters:

pTaps:- Pointer to the array containing the taps. The number of
elements in the array is 2*(order+1) for arbitrary filters and 6*numBq
for BQ filters.i.e. This is the array of coeffiecients A0, A1, A2 AND BO,
B1, B2 (for bi-quad)

tapsFactor:- Scale factor for the taps of Ipp32s data type
(for integer versions only)

numBq:- Number of cascades of biquads. This argument is used for BQ
filters.

order:- Order of the IIR filter. This argument is used for arbitrary
filters.

pDlyLine:- Pointer to the array containing the delay line values. The
number of elements in the array is order for arbitrary filters and
2*numBq for BQ filters.

pState:- Pointer to the IIR state structure to be created.
	We have certain formulae for the coeffiecients which require the
Bandwidth or Quality factor to calculate the coefficients.

So how to get the Bandwidth for Lowpass or highpass filter if we have
the slope in db/oct.....

Hoping for valuable help in this matter and thankyou very much for
giving your precious time.
	

----- Original Message -----

From: c...@rediffmail.com

To: a...@yahoogroups.com

Sent: Thursday, March 03, 2005 4:09 AM

Subject: [audiodsp] How to design an IIR filter using slope(db/oct) information

Topic : To design an IIR HPF filter using IPP(Intel Integrated Performance
Primitives) library.
Current need: to calculate BW or Q from slope.

The specification of filter is :
Cutt-off frequency : in Hz
Slope : in dB/oct

We are having an IPP library which has IIR filter implementation
function. This function has following parameters:

pTaps:- Pointer to the array containing the taps. The number of
elements in the array is 2*(order+1) for arbitrary filters and 6*numBq
for BQ filters.i.e. This is the array of coeffiecients A0, A1, A2 AND BO,
B1, B2 (for bi-quad)

tapsFactor:- Scale factor for the taps of Ipp32s data type
(for integer versions only)

numBq:- Number of cascades of biquads. This argument is used for BQ
filters.

order:- Order of the IIR filter. This argument is used for arbitrary
filters.

pDlyLine:- Pointer to the array containing the delay line values. The
number of elements in the array is order for arbitrary filters and
2*numBq for BQ filters.

pState:- Pointer to the IIR state structure to be created.We have certain formulae for the coeffiecients which require the
Bandwidth or Quality factor to calculate the coefficients.

So how to get the Bandwidth for Lowpass or highpass filter if we have
the slope in db/oct.....

Hoping for valuable help in this matter and thankyou very much for
giving your precious time.



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Hi,

If you're designing filters, and are uncertain exactly what you need to
do, then I'd strongly recommend having a play with Matlab.  It's quite
simply an amazing bit of software.  Specifically, try the "fdatool"
command.  You can read more at:

http://www.mathworks.com/access/helpdesk/help/toolbox/signal/fdatool.html

In general, you define bandwidth by considering a point at which the
filter's response is more than X dB different to the pass/stop band.  A
filter will have a sharper drop off if it has more coefficients.

Good luck,

Rob
	Mike wrote:
> The BW and slope are generally independant.  
> I am not sure why the Q-factor is of interest, in your case.  There's
a
> lot of different things I could say about the Q-factor, but I won't
> since I don't know if you care.
>  
> The slope will drive the order of the filter, i.e.  a sharper or higher
> slope requirements leads to a higher order filter and therefore more
> bi-quad section.
> For each biquad section you will need a set of coefficients (A0, A1, A2
> AND BO,
> B1, B2 ).
>  
> Mike.
> 
>     ----- Original Message -----
>     *From:* career4krish@care...
>     <mailto:career4krish@care...>
>     *To:* audiodsp@audi... <mailto:audiodsp@audi...>
>     *Sent:* Thursday, March 03, 2005 4:09 AM
>     *Subject:* [audiodsp] How to design an IIR filter using
>     slope(db/oct) information
> 
> 
>     Topic : To design an IIR HPF filter using IPP(Intel Integrated
>     Performance
>     Primitives) library.
>     Current need: to calculate BW or Q from slope.
> 
>     The specification of filter is :
>     Cutt-off frequency : in Hz
>     Slope : in dB/oct
> 
>     We are having an IPP library which has IIR filter implementation
>     function. This function has following parameters:
> 
>     pTaps:- Pointer to the array containing the taps. The number of
>     elements in the array is 2*(order+1) for arbitrary filters and
6*numBq
>     for BQ filters.i.e. This is the array of coeffiecients A0, A1, A2
>     AND BO,
>     B1, B2 (for bi-quad)
> 
>     tapsFactor:- Scale factor for the taps of Ipp32s data type
>     (for integer versions only)
> 
>     numBq:- Number of cascades of biquads. This argument is used for BQ
>     filters.
> 
>     order:- Order of the IIR filter. This argument is used for arbitrary
>     filters.
> 
>     pDlyLine:- Pointer to the array containing the delay line values. The
>     number of elements in the array is order for arbitrary filters and
>     2*numBq for BQ filters.
> 
>     pState:- Pointer to the IIR state structure to be created.
> 
> 
>     We have certain formulae for the coeffiecients which require the
>     Bandwidth or Quality factor to calculate the coefficients.
> 
>     So how to get the Bandwidth for Lowpass or highpass filter if we have
>     the slope in db/oct.....
> 
>     Hoping for valuable help in this matter and thankyou very much for
>     giving your precious time.
> 
> 
> 
> 
> 
> 
>     *
> 
>         * To <http://docs.yahoo.com/info/terms/>. 
> 
> 

I've had good results with Scope FIR also, and considerably less
expensive 
than Matlab, I believe.
http://www.iowegian.com/

At 10:13 AM 3/9/2005, Robert Shilston wrote:

>Hi,
>
>If you're designing filters, and are uncertain exactly what you need to
>do, then I'd strongly recommend having a play with Matlab.  It's
quite
>simply an amazing bit of software.  Specifically, try the
"fdatool"
>command.  You can read more at:
>
>http://www.mathworks.com/access/helpdesk/help/toolbox/signal/fdatool.html
>
>In general, you define bandwidth by considering a point at which the
>filter's response is more than X dB different to the pass/stop band.  A
>filter will have a sharper drop off if it has more coefficients.
>
>Good luck,
>
>Rob
>
>
>Mike wrote:
> > The BW and slope are generally independant.
> > I am not sure why the Q-factor is of interest, in your case. 
There's a
> > lot of different things I could say about the Q-factor, but I
won't
> > since I don't know if you care.
> >
> > The slope will drive the order of the filter, i.e.  a sharper or
higher
> > slope requirements leads to a higher order filter and therefore more
> > bi-quad section.
> > For each biquad section you will need a set of coefficients (A0, A1,
A2
> > AND BO,
> > B1, B2 ).
> >
> > Mike.
> >
> >     ----- Original Message -----
> >     *From:* career4krish@care...
> >     <mailto:career4krish@care...>
> >     *To:* audiodsp@audi... <mailto:audiodsp@audi...>
> >     *Sent:* Thursday, March 03, 2005 4:09 AM
> >     *Subject:* [audiodsp] How to design an IIR filter using
> >     slope(db/oct) information
> >
> >
> >     Topic : To design an IIR HPF filter using IPP(Intel Integrated
> >     Performance
> >     Primitives) library.
> >     Current need: to calculate BW or Q from slope.
> >
> >     The specification of filter is :
> >     Cutt-off frequency : in Hz
> >     Slope : in dB/oct
> >
> >     We are having an IPP library which has IIR filter implementation
> >     function. This function has following parameters:
> >
> >     pTaps:- Pointer to the array containing the taps. The number of
> >     elements in the array is 2*(order+1) for arbitrary filters and
6*numBq
> >     for BQ filters.i.e. This is the array of coeffiecients A0, A1, A2
> >     AND BO,
> >     B1, B2 (for bi-quad)
> >
> >     tapsFactor:- Scale factor for the taps of Ipp32s data type
> >     (for integer versions only)
> >
> >     numBq:- Number of cascades of biquads. This argument is used for
BQ
> >     filters.
> >
> >     order:- Order of the IIR filter. This argument is used for
arbitrary
> >     filters.
> >
> >     pDlyLine:- Pointer to the array containing the delay line values.
The
> >     number of elements in the array is order for arbitrary filters and
> >     2*numBq for BQ filters.
> >
> >     pState:- Pointer to the IIR state structure to be created.
> >
> >
> >     We have certain formulae for the coeffiecients which require the
> >     Bandwidth or Quality factor to calculate the coefficients.
> >
> >     So how to get the Bandwidth for Lowpass or highpass filter if we
have
> >     the slope in db/oct.....
> >
> >     Hoping for valuable help in this matter and thankyou very much for
> >     giving your precious time.
> >
> >
> >
> >
> >
> >
> >     *
> >
> >         * To <http://docs.yahoo.com/info/terms/>.
> >
> >
>
>

Steve Holle
Link Communications, Inc.
1035 Cerise Rd.
Billings, MT  59101
sholle@shol...
	

If you want a free tool,have a look at Scilab:
http://scilabsoft.inria.fr/
-----Original Message-----
From: Steve Holle [mailto:s...@link-comm.com]
Sent: Thu 3/10/2005 1:00 AM
To: Robert Shilston; c...@rediffmail.com
Cc: Mike; a...@yahoogroups.com
Subject: Re: [audiodsp] How to design an IIR filter using slope(db/oct)  information I've had good results with Scope FIR also, and considerably less expensive
than Matlab, I believe.
http://www.iowegian.com/

At 10:13 AM 3/9/2005, Robert Shilston wrote:

>Hi,
>
>If you're designing filters, and are uncertain exactly what you need to
>do, then I'd strongly recommend having a play with Matlab.  It's quite
>simply an amazing bit of software.  Specifically, try the "fdatool"
>command.  You can read more at:
>
>http://www.mathworks.com/access/helpdesk/help/toolbox/signal/fdatool.html
>
>In general, you define bandwidth by considering a point at which the
>filter's response is more than X dB different to the pass/stop band.  A
>filter will have a sharper drop off if it has more coefficients.
>
>Good luck,
>
>Rob >Mike wrote:
> > The BW and slope are generally independant.
> > I am not sure why the Q-factor is of interest, in your case.  There's a
> > lot of different things I could say about the Q-factor, but I won't
> > since I don't know if you care.
> >
> > The slope will drive the order of the filter, i.e.  a sharper or higher
> > slope requirements leads to a higher order filter and therefore more
> > bi-quad section.
> > For each biquad section you will need a set of coefficients (A0, A1, A2
> > AND BO,
> > B1, B2 ).
> >
> > Mike.
> >
> >     ----- Original Message -----
> >     *From:* c...@rediffmail.com
> >     <mailto:c...@rediffmail.com>
> >     *To:* a...@yahoogroups.com <mailto:a...@yahoogroups.com>
> >     *Sent:* Thursday, March 03, 2005 4:09 AM
> >     *Subject:* [audiodsp] How to design an IIR filter using
> >     slope(db/oct) information
> >
> >
> >     Topic : To design an IIR HPF filter using IPP(Intel Integrated
> >     Performance
> >     Primitives) library.
> >     Current need: to calculate BW or Q from slope.
> >
> >     The specification of filter is :
> >     Cutt-off frequency : in Hz
> >     Slope : in dB/oct
> >
> >     We are having an IPP library which has IIR filter implementation
> >     function. This function has following parameters:
> >
> >     pTaps:- Pointer to the array containing the taps. The number of
> >     elements in the array is 2*(order+1) for arbitrary filters and 6*numBq
> >     for BQ filters.i.e. This is the array of coeffiecients A0, A1, A2
> >     AND BO,
> >     B1, B2 (for bi-quad)
> >
> >     tapsFactor:- Scale factor for the taps of Ipp32s data type
> >     (for integer versions only)
> >
> >     numBq:- Number of cascades of biquads. This argument is used for BQ
> >     filters.
> >
> >     order:- Order of the IIR filter. This argument is used for arbitrary
> >     filters.
> >
> >     pDlyLine:- Pointer to the array containing the delay line values. The
> >     number of elements in the array is order for arbitrary filters and
> >     2*numBq for BQ filters.
> >
> >     pState:- Pointer to the IIR state structure to be created.
> >
> >
> >     We have certain formulae for the coeffiecients which require the
> >     Bandwidth or Quality factor to calculate the coefficients.
> >
> >     So how to get the Bandwidth for Lowpass or highpass filter if we have
> >     the slope in db/oct.....
> >
> >     Hoping for valuable help in this matter and thankyou very much for
> >     giving your precious time.
> >
> >
> >
> >
> >
> >
> >     *
> >
> >         * To <http://docs.yahoo.com/info/terms/>.
> >
>
Steve Holle
Link Communications, Inc.
1035 Cerise Rd.
Billings, MT  59101
s...@link-comm.com