how to adjust poles and zeros for reducing error

hi,

I am designing a deemphasis filter of 15/50us specification. I am using
using bilinear transform method. But at frequencies near to nyquist
frequency I am getting an error of 1dB. I tried pre wrapping. But I gives
error reduction only at the frequency where the wrapping is applied. 

So I would like go for pole zero adjustment to reduce the error. What are
the guidelines that I should follow while adjusting the pole and zero (I
am dealing with first order filter). Is there any tutorials or pdf
available, which I can follow...?


---------------------------------------
Posted through http://www.DSPRelated.com

"alpha1" <103600@DSPRelated> writes:

> hi,
>
> I am designing a deemphasis filter of 15/50us specification. I am using
> using bilinear transform method. But at frequencies near to nyquist
> frequency I am getting an error of 1dB. I tried pre wrapping. But I gives
> error reduction only at the frequency where the wrapping is applied. 
>
> So I would like go for pole zero adjustment to reduce the error. What are
> the guidelines that I should follow while adjusting the pole and zero (I
> am dealing with first order filter). Is there any tutorials or pdf
> available, which I can follow...?

I would suggest using the FDLS (Frequency Domain Least Squares) filter
design method instead. It is superb for simulating filters like this,
i.e., analog filter magnitude and phase. Greg Berchin has written
much about it - google his name and these phrases.
-- 
Randy Yates
Digital Signal Labs
http://www.digitalsignallabs.com

On 5/14/2015 12:59 PM, alpha1 wrote:

> So I would like go for pole zero adjustment to reduce the error. What are
> the guidelines that I should follow while adjusting the pole and zero (I
> am dealing with first order filter). Is there any tutorials or pdf
> available, which I can follow...?
>

There is a Mathematica applet here

"Transfer Function Analysis by Manipulation of Poles and Zeros"

Which allows ones to see the effect of changing locations of poles
and zeros. Drag a pole or a zero using the mouse and see
the effect.

Need a free reader to run it. The free reader is here:

https://www.wolfram.com/cdf-player/

On Thu, 14 May 2015 12:59:43 -0500, "alpha1" <103600@DSPRelated> wrote:

>I am designing a deemphasis filter of 15/50us specification. I am using
>using bilinear transform method. But at frequencies near to nyquist
>frequency I am getting an error of 1dB. I tried pre wrapping. But I gives
>error reduction only at the frequency where the wrapping is applied. 

https://groups.google.com/d/topic/comp.dsp/WSMrkyEcBBo/discussion
Eight years and twelve days. Time flies. 

Send email directly to me if you want code for FDLS. Change "chatter" to
"charter" and drop ".invalid".

>On Thu, 14 May 2015 12:59:43 -0500, "alpha1" <103600@DSPRelated> wrote:
>
>>I am designing a deemphasis filter of 15/50us specification. I am using
>>using bilinear transform method. But at frequencies near to nyquist
>>frequency I am getting an error of 1dB. I tried pre wrapping. But I
gives
>>error reduction only at the frequency where the wrapping is applied. 
>
>https://groups.google.com/d/topic/comp.dsp/WSMrkyEcBBo/discussion
>Eight years and twelve days. Time flies. 
>
>Send email directly to me if you want code for FDLS. Change "chatter" to
>"charter" and drop ".invalid".

Dear Greg Berchin,

Could you please share your e-mail ID?

Thanks in advance.
---------------------------------------
Posted through http://www.DSPRelated.com

On Tue, 09 Jun 2015 02:31:20 -0500, "alpha1" <103600@DSPRelated> wrote:

>Dear Greg Berchin,
>
>Could you please share your e-mail ID?
>
>Thanks in advance.

"I'm sorry, (alpha1). I'm afraid I can't do that."

Instead find the original comp.dsp thread at
https://groups.google.com/forum/#!original/comp.dsp/wvD_EPWgnek/NDywVIz6qlMJ
and locate my obfuscated address in the "From:" field there. Make the
changes that I detail in the message, and you'll have my email address.

Greg

Hi,

I went through
https://groups.google.com/forum/#!original/comp.dsp/wvD_EPWgnek/NDywVIz6qlMJ
I saw that Robert's poles and zeros at 48khz are really matching with the
analog response. I used these poles and zeros and mapped them to poles and
zeros at 44.1khz using BLT. I got error of 0.15dB only. But when I go for
32Khz or 24Khz the error is more than 0.5dB . I see Greg's and Robert's
solutions are excellent. Can anyone help me with their design methods.

Thanks in advance
---------------------------------------
Posted through http://www.DSPRelated.com

On 6/16/15 8:30 AM, alpha1 wrote:
> Hi,
>
> I went through
> https://groups.google.com/forum/#!original/comp.dsp/wvD_EPWgnek/NDywVIz6qlMJ
> I saw that Robert's poles and zeros at 48khz are really matching with the
> analog response. I used these poles and zeros and mapped them to poles and
> zeros at 44.1khz using BLT. I got error of 0.15dB only. But when I go for
> 32Khz or 24Khz the error is more than 0.5dB . I see Greg's and Robert's
> solutions are excellent. Can anyone help me with their design methods.

dunno fer sure who "Robert" is.  i don't remember any solution i have 
ever done for a 15/50 microsecond deemphasis filter.

-- 

r b-j                  rbj@audioimagination.com

"Imagination is more important than knowledge."

On Tue, 16 Jun 2015 11:48:24 -0400, robert bristow-johnson
<rbj@audioimagination.com> wrote:

>dunno fer sure who "Robert" is.  i don't remember any solution i have 
>ever done for a 15/50 microsecond deemphasis filter.

He's referring to Robert Orban.

https://groups.google.com/d/msg/comp.dsp/9kuirTaABzg/CSg4hgh0saoJ

>On Tue, 16 Jun 2015 11:48:24 -0400, robert bristow-johnson
><rbj@audioimagination.com> wrote:
>
>>dunno fer sure who "Robert" is.  i don't remember any solution i have 
>>ever done for a 15/50 microsecond deemphasis filter.
>
>He's referring to Robert Orban.
>
>https://groups.google.com/d/msg/comp.dsp/9kuirTaABzg/CSg4hgh0saoJ

yeah, Robert Orban.... I think Robert Orban's and Greg Berchin methods
would realise an analog transfer function in digital domain with minimum
error.... I am going through these methods....

@ Greg I have mailed u...My name is sharvin
---------------------------------------
Posted through http://www.DSPRelated.com