> On Mar 12, 4:42 pm, Jerry Avins <j...@ieee.org> wrote:
>> Ron N. wrote:
>>> On Mar 12, 11:04 am, Oli Charlesworth <ca...@olifilth.co.uk> wrote:
>>>> On Mar 12, 5:58 pm, "bharat pathak" <bha...@arithos.com> wrote:
>>>>> Hi,
>>>>> I am seeing some negative group delay at
>>>>> 1000, 2000, 3000, 4000, 5000 Hz. The example
>>>>> filter listed below with matlab/octave code.
>>>>> any clue why this is happening? interesting
>>>>> part is when I feed 1000 hz sine wave sampled
>>>>> at 10000 hz I don't see the behaviour of
>>>>> negative group delay.
>>>> Individual sine waves don't experience group delay, they experience
>>>> phase delay.
>>> Yes. To see the group delay you will have to modulate your
>>> sine wave while staying completely within a bandwidth where
>>> the group delay is fairly constant, and then compare the
>>> before and after filtering locations of your modulation
>>> envelope.
>> No modulation needed. three signals close in frequency and amplitude
>> will produce beats that _look_ like modulation and illustrate the effect.
>
> Well, I sort of agree. But call any two of those sinusoids
> the sidebands produced by complex modulation of the third,
> and I think the sum is identical to a form of modulation
> with carrier.
Modulation (according to me) is a non-linear process (multiplication,
rectification, etc). Summation is not. Both produce envelopes, but the
details of those envelopes differ.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Ron N.●March 12, 20082008-03-12
On Mar 12, 4:42 pm, Jerry Avins <j...@ieee.org> wrote:
> Ron N. wrote:
> > On Mar 12, 11:04 am, Oli Charlesworth <ca...@olifilth.co.uk> wrote:
> >> On Mar 12, 5:58 pm, "bharat pathak" <bha...@arithos.com> wrote:
>
> >>> Hi,
> >>> I am seeing some negative group delay at
> >>> 1000, 2000, 3000, 4000, 5000 Hz. The example
> >>> filter listed below with matlab/octave code.
> >>> any clue why this is happening? interesting
> >>> part is when I feed 1000 hz sine wave sampled
> >>> at 10000 hz I don't see the behaviour of
> >>> negative group delay.
> >> Individual sine waves don't experience group delay, they experience
> >> phase delay.
>
> > Yes. To see the group delay you will have to modulate your
> > sine wave while staying completely within a bandwidth where
> > the group delay is fairly constant, and then compare the
> > before and after filtering locations of your modulation
> > envelope.
>
> No modulation needed. three signals close in frequency and amplitude
> will produce beats that _look_ like modulation and illustrate the effect.
Well, I sort of agree. But call any two of those sinusoids
the sidebands produced by complex modulation of the third,
and I think the sum is identical to a form of modulation
with carrier.
Reply by Jerry Avins●March 12, 20082008-03-12
Ron N. wrote:
> On Mar 12, 11:04 am, Oli Charlesworth <ca...@olifilth.co.uk> wrote:
>> On Mar 12, 5:58 pm, "bharat pathak" <bha...@arithos.com> wrote:
>>
>>> Hi,
>>> I am seeing some negative group delay at
>>> 1000, 2000, 3000, 4000, 5000 Hz. The example
>>> filter listed below with matlab/octave code.
>>> any clue why this is happening? interesting
>>> part is when I feed 1000 hz sine wave sampled
>>> at 10000 hz I don't see the behaviour of
>>> negative group delay.
>> Individual sine waves don't experience group delay, they experience
>> phase delay.
>
> Yes. To see the group delay you will have to modulate your
> sine wave while staying completely within a bandwidth where
> the group delay is fairly constant, and then compare the
> before and after filtering locations of your modulation
> envelope.
No modulation needed. three signals close in frequency and amplitude
will produce beats that _look_ like modulation and illustrate the effect.
Jerry
--
Engineering is the art of making what you want from things you can get.
�����������������������������������������������������������������������
Reply by Ron N.●March 12, 20082008-03-12
On Mar 12, 11:04 am, Oli Charlesworth <ca...@olifilth.co.uk> wrote:
> On Mar 12, 5:58 pm, "bharat pathak" <bha...@arithos.com> wrote:
>
> > Hi,
>
> > I am seeing some negative group delay at
> > 1000, 2000, 3000, 4000, 5000 Hz. The example
> > filter listed below with matlab/octave code.
>
> > any clue why this is happening? interesting
> > part is when I feed 1000 hz sine wave sampled
> > at 10000 hz I don't see the behaviour of
> > negative group delay.
>
> Individual sine waves don't experience group delay, they experience
> phase delay.
Yes. To see the group delay you will have to modulate your
sine wave while staying completely within a bandwidth where
the group delay is fairly constant, and then compare the
before and after filtering locations of your modulation
envelope.
Reply by Oli Charlesworth●March 12, 20082008-03-12
On Mar 12, 5:58 pm, "bharat pathak" <bha...@arithos.com> wrote:
> Hi,
>
> I am seeing some negative group delay at
> 1000, 2000, 3000, 4000, 5000 Hz. The example
> filter listed below with matlab/octave code.
>
> any clue why this is happening? interesting
> part is when I feed 1000 hz sine wave sampled
> at 10000 hz I don't see the behaviour of
> negative group delay.
Individual sine waves don't experience group delay, they experience
phase delay.
--
Oli
Reply by bharat pathak●March 12, 20082008-03-12
Hi,
I am seeing some negative group delay at
1000, 2000, 3000, 4000, 5000 Hz. The example
filter listed below with matlab/octave code.
any clue why this is happening? interesting
part is when I feed 1000 hz sine wave sampled
at 10000 hz I don't see the behaviour of
negative group delay.
Regards
Bharat
%----------------------------------------------------------------
clear;
close all;
h1 = [10 9 8 7 6 5 4 3 2 1]/55;
Fs = 10000;
[gd, f] = grpdelay(h1, 1, 8192, Fs);
figure; clf;
plot(f, gd);