"Rick Lyons" <r.lyons@_BOGUS_ieee.org> wrote in message
news:40c37201.78962218@news.sf.sbcglobal.net...
> I wonder if there's a way to implement your
> desired processing *without* using the
> Hilbert transform(?).
Well, you could use a complex IIR to isolate one sideband directly.
I suggest using a complex filter on the audio instead of a real lowpass on a
frequency-shifted version, because of the different widths of the upper and
lower transition regions.
I don't know of any tools to make designing such things a lot easier. I
would try it like this:
1) Make a real analog Butterworth lowpass;
2) Shift all the poles and zeros up on the jw axis, until you have good
attenuation at DC;
3) Convert to analog with the bilinear transform; and finally
4) swap the poles and zeros left to right (by negating the real component).
The idea is that, by varying the parameters to the bilinear transform, you
could use its frequency warping to produce a much sharper transition at
Nyquist, when you would then move to DC, where it's needed.
I haven't verified that it works, but if I had the OP's problem, I would
give it a try. Perhaps someone with a lot of IIR experience can comment on
the viability of this technique.
Reply by Rick Lyons●June 6, 20042004-06-06
On Fri, 04 Jun 2004 21:54:14 +0100, scott@scottincz.com wrote:
>What would be the most effecient method of hilbert transofrming audio?
>my filter program genertates too many taps for the low frequency
>performacnce i require. I don't want to use FFT due to memory
>constraints in the DSP.
>Thanks in advance
Hi,
Whew Scott! What you're trying to
do is *VERY* computationally intensive.
There are several ways to compute Hilbert
transforms (to generate "analytic signals"), but
as you're finding out, it may be impossible
for you to compute an accurate Hilbert transform
of a signal over the freq range of
30 Hz -to- 20 KHz when the sample
rate is 48 KHz.
It's possible to compute an accurate Hilbert
transform of a signal over the narrow freq
range of 30 Hz -to- 100 Hz when the sample
rate is 48 KHz, using an "interpolated-coefficient
filter" scheme, but to perform accurate Hilbert
transforms over a 20 KHz range you'll
need a fantastic amount of number-crunching
power.
I wonder if there's a way to implement your
desired processing *without* using the
Hilbert transform(?).
Good Luck,
[-Rick-]
Reply by Jerry Avins●June 6, 20042004-06-06
scott@scottincz.com wrote:
> On Sat, 05 Jun 2004 17:19:22 -0400, Jerry Avins <jya@ieee.org> wrote:
>
>
>>scott@scottincz.com wrote:
>>
>>
>>>>If you want real numbers, you'll have to divulge the sample rate and the
>>>>passband of the anti-alias filter.
>>>
>>>
>>>
>>>How about 48Khz 20Hz-20Khz
>>>
>>>
>>>
>>>>Jerry
>>
>>What is the actual bandwidth of your signal? (This is, as my father
>>would say, like pulling teeth.)
>
>
> 20Hz-20Khz, already stated in the previous post.
>
>
>
>>Jerry
You stated that the range of interest is 20Hz-20KHz. Are you assured
that there are no significant components above 20 KHz that can interfere
with a design which assumes their absence? Maybe it doesn't matter.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by ●June 6, 20042004-06-06
On Sat, 05 Jun 2004 17:19:22 -0400, Jerry Avins <jya@ieee.org> wrote:
>scott@scottincz.com wrote:
>
>>>If you want real numbers, you'll have to divulge the sample rate and the
>>>passband of the anti-alias filter.
>>
>>
>>
>> How about 48Khz 20Hz-20Khz
>>
>>
>>>Jerry
>
>What is the actual bandwidth of your signal? (This is, as my father
>would say, like pulling teeth.)
20Hz-20Khz, already stated in the previous post.
>
>Jerry
Reply by Jerry Avins●June 5, 20042004-06-05
scott@scottincz.com wrote:
>>If you want real numbers, you'll have to divulge the sample rate and the
>>passband of the anti-alias filter.
>
>
>
> How about 48Khz 20Hz-20Khz
>
>
>>Jerry
What is the actual bandwidth of your signal? (This is, as my father
would say, like pulling teeth.)
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by ●June 5, 20042004-06-05
>If you want real numbers, you'll have to divulge the sample rate and the
>passband of the anti-alias filter.
How about 48Khz 20Hz-20Khz
>
>Jerry
Reply by Jerry Avins●June 5, 20042004-06-05
scott@scottincz.com wrote:
> On Sat, 05 Jun 2004 11:07:33 -0400, Jerry Avins <jya@ieee.org> wrote:
>
>
>>David Joseph Bonnici wrote:
>>
>>
>>>I suggest the use of the following.
>>>http://www.nauticom.net/www/jdtaft/special_fir.htm
>>>
>>>David
>>
>>OP wants not a HT, but something to do his job faster. We're trying to
>>find out how much of what else he can give up to get it.
>
>
> What i require is good amplitude performance at low frequencies, say
> 30-50 Hz but i also need the audio to extend up to 20khz. At the
> moment the taps come out in the thousands for the performance i am
> after. The hardware won't allow FFT.
> The application is the removal of the lower sideband in an AM
> modulator.
>
>
>
>>Thanks for the link. It's a nice one.
>>
>>Jerry
If you want real numbers, you'll have to divulge the sample rate and the
passband of the anti-alias filter.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by ●June 5, 20042004-06-05
On Sat, 05 Jun 2004 11:07:33 -0400, Jerry Avins <jya@ieee.org> wrote:
>David Joseph Bonnici wrote:
>
>> I suggest the use of the following.
>> http://www.nauticom.net/www/jdtaft/special_fir.htm
>>
>> David
>
>OP wants not a HT, but something to do his job faster. We're trying to
>find out how much of what else he can give up to get it.
What i require is good amplitude performance at low frequencies, say
30-50 Hz but i also need the audio to extend up to 20khz. At the
moment the taps come out in the thousands for the performance i am
after. The hardware won't allow FFT.
The application is the removal of the lower sideband in an AM
modulator.
OP wants not a HT, but something to do his job faster. We're trying to
find out how much of what else he can give up to get it.
Thanks for the link. It's a nice one.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by David Joseph Bonnici●June 5, 20042004-06-05