On Feb 22, 1:42 am, Rune Allnor <all...@tele.ntnu.no> wrote:
> On 21 Feb, 20:41, "Ron N." <rhnlo...@yahoo.com> wrote:
>
>
>
> > On Feb 21, 11:03 am, Rune Allnor <all...@tele.ntnu.no> wrote:
>
> > > On 21 Feb, 19:40, "Ron N." <rhnlo...@yahoo.com> wrote:
>
> > > > On Feb 21, 10:25 am, Rune Allnor <all...@tele.ntnu.no> wrote:
>
> > > > > On 21 Feb, 18:50, "Ron N." <rhnlo...@yahoo.com> wrote:
>
> > > > > > Communication using phase modulation requires
> > > > > > some form of phase detection, elusive situation or not.
>
> > > > > And the relevance of this wrt the phase spectrum is...?
>
> > > > The phase spectrum contains information about a signals
> > > > phase in relationship to the window and/or data aperture.
>
> > > That's a no-brainer. I was wondering what the connection
> > > is between phase modulation and the phase spectrum. Since
> > > you mention phase modulation in a thread concerning the
> > > phase spectrum I assume you know of a connection?
> > > Maybe a demodulation technique which is based on
> > > the phase spectrum?
>
> > The one I know of is used in an attempt to recover telemetry
> > data from deep space probes.
>
> I did not ask if you know of a phase modulation technique which
> works. I asked if you know of a phase modulation technique
> which is based on computing the phase spectrum, as opposed to
> some time-domain democulation technique.
You'll have to ask the deep space communications experts.
My limited understanding is that the deepest working
space probes were designed before digital frequency
domain techniques were even computationally feasible.
Reply by Rune Allnor●February 22, 20082008-02-22
On 21 Feb, 20:41, "Ron N." <rhnlo...@yahoo.com> wrote:
> On Feb 21, 11:03 am, Rune Allnor <all...@tele.ntnu.no> wrote:
>
>
>
>
>
> > On 21 Feb, 19:40, "Ron N." <rhnlo...@yahoo.com> wrote:
>
> > > On Feb 21, 10:25 am, Rune Allnor <all...@tele.ntnu.no> wrote:
>
> > > > On 21 Feb, 18:50, "Ron N." <rhnlo...@yahoo.com> wrote:
>
> > > > > Communication using phase modulation requires
> > > > > some form of phase detection, elusive situation or not.
>
> > > > And the relevance of this wrt the phase spectrum is...?
>
> > > The phase spectrum contains information about a signals
> > > phase in relationship to the window and/or data aperture.
>
> > That's a no-brainer. I was wondering what the connection
> > is between phase modulation and the phase spectrum. Since
> > you mention phase modulation in a thread concerning the
> > phase spectrum I assume you know of a connection?
> > Maybe a demodulation technique which is based on
> > the phase spectrum?
>
> The one I know of is used in an attempt to recover telemetry
> data from deep space probes.
I did not ask if you know of a phase modulation technique which
works. I asked if you know of a phase modulation technique
which is based on computing the phase spectrum, as opposed to
some time-domain democulation technique.
Rune
Reply by Ron N.●February 21, 20082008-02-21
On Feb 21, 8:16 am, "bharat pathak" <bha...@arithos.com> wrote:
> Hello All,
>
> I want to understand how spectral leakage changes the
> phase spectrum of a sine wave?
A sinusoid which is periodic in a DFT aperture will have
the same phase relationship to the beginning and end of the
aperture and a very closely related (identical modulo pi)
phase in the middle.
A sinusoid which is not periodic in the aperture will not have
the same phase at the beginning and end of the aperture for
any of the DFT bin frequencies. The information about the
ratio of odd to even function will be spread out far and wide
into many bins (in the shape of the transform of the window,
called "leakage"). The frequency transform of non-periodic
sinusoid can also be interfered with from its own negative
frequency image near DC or Fs/2. Thus the phase content
of the nearest magnitude peak bin may not be exactly
representative of any reference phase to some fixed point
in the window, as would be true in the case of an exactly
periodic in the aperture sinusoid.
Windowing, with something like a raised-cosine, Gaussian, or
Blackman-Nuttall, will chop off most of the discontinuity near
the window's ends, and pull most of the "leakage" into a more
central location, where information (including magnitude and
the oddness/evenness ratio) can be more easily and locally
interpolated.
IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M
Reply by Ron N.●February 21, 20082008-02-21
On Feb 21, 11:03 am, Rune Allnor <all...@tele.ntnu.no> wrote:
> On 21 Feb, 19:40, "Ron N." <rhnlo...@yahoo.com> wrote:
>
> > On Feb 21, 10:25 am, Rune Allnor <all...@tele.ntnu.no> wrote:
>
> > > On 21 Feb, 18:50, "Ron N." <rhnlo...@yahoo.com> wrote:
>
> > > > Communication using phase modulation requires
> > > > some form of phase detection, elusive situation or not.
>
> > > And the relevance of this wrt the phase spectrum is...?
>
> > The phase spectrum contains information about a signals
> > phase in relationship to the window and/or data aperture.
>
> That's a no-brainer. I was wondering what the connection
> is between phase modulation and the phase spectrum. Since
> you mention phase modulation in a thread concerning the
> phase spectrum I assume you know of a connection?
> Maybe a demodulation technique which is based on
> the phase spectrum?
The one I know of is used in an attempt to recover telemetry
data from deep space probes.
IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M
Reply by Rune Allnor●February 21, 20082008-02-21
On 21 Feb, 19:40, "Ron N." <rhnlo...@yahoo.com> wrote:
> On Feb 21, 10:25 am, Rune Allnor <all...@tele.ntnu.no> wrote:
>
> > On 21 Feb, 18:50, "Ron N." <rhnlo...@yahoo.com> wrote:
>
> > > Communication using phase modulation requires
> > > some form of phase detection, elusive situation or not.
>
> > And the relevance of this wrt the phase spectrum is...?
>
> The phase spectrum contains information about a signals
> phase in relationship to the window and/or data aperture.
That's a no-brainer. I was wondering what the connection
is between phase modulation and the phase spectrum. Since
you mention phase modulation in a thread concerning the
phase spectrum I assume you know of a connection?
Maybe a demodulation technique which is based on
the phase spectrum?
Rune
Reply by Ron N.●February 21, 20082008-02-21
On Feb 21, 10:25 am, Rune Allnor <all...@tele.ntnu.no> wrote:
> On 21 Feb, 18:50, "Ron N." <rhnlo...@yahoo.com> wrote:
>
> > Communication using phase modulation requires
> > some form of phase detection, elusive situation or not.
>
> And the relevance of this wrt the phase spectrum is...?
The phase spectrum contains information about a signals
phase in relationship to the window and/or data aperture.
Reply by Rune Allnor●February 21, 20082008-02-21
On 21 Feb, 18:50, "Ron N." <rhnlo...@yahoo.com> wrote:
>�Communication using phase modulation requires
> some form of phase detection, elusive situation or not.
And the relevance of this wrt the phase spectrum is...?
Rune
Reply by Ron N.●February 21, 20082008-02-21
On Feb 21, 9:18 am, Rune Allnor <all...@tele.ntnu.no> wrote:
> On 21 Feb, 17:16, "bharat pathak" <bha...@arithos.com> wrote:
>
> > After performing windowing, how reliable is the phase
> > information and what information can be deduced from
> > the phase plot (post windowing).
>
> Phase information is inherently elusive, and messing around
> with phase spectra is a can of worms at the best of times.
> Just accept the fact that the phase spectrum changes by
> windowing, and leave it at that. I don't think there are
> very many applications where there is a justifiable need
> to reconstruct the 'true' phase spectrum.
Phase information is useful for analyzing data across
successive or overlapped DFT frames (see "phase vocoder").
Phase information also appears important for accurate
frequency estimation near DC or Fs/2. Relative phase
information is required to correctly reconstruct a time
or spatial domain waveform (say edges in a photographic
image). Communication using phase modulation requires
some form of phase detection, elusive situation or not.
Different windows do affect the phase information (or
ratio between oddness and evenness) differently for
different frequencies. Sometimes this affect can be
compensated for.
IMHO. YMMV.
--
rhn A.T nicholson d.0.t C-o-M
Reply by Rune Allnor●February 21, 20082008-02-21
On 21 Feb, 17:16, "bharat pathak" <bha...@arithos.com> wrote:
> � � � After performing windowing, how reliable is the phase
> � � � information and what information can be deduced from
> � � � the phase plot (post windowing).
Phase information is inherently elusive, and messing around
with phase spectra is a can of worms at the best of times.
Just accept the fact that the phase spectrum changes by
windowing, and leave it at that. I don't think there are
very many applications where there is a justifiable need
to reconstruct the 'true' phase spectrum.
Rune
Reply by bharat pathak●February 21, 20082008-02-21
Hello All,
I want to understand how spectral leakage changes the
phase spectrum of a sine wave?
Also when I apply window (blackman harris 11 Term or
chebyshev window with 300db attenuation), I see a
significant amount of reduction in spectral leakage
in the amplitude part of the spectrum.
But this windowing also affects the phase part of the
spectrum.
After performing windowing, how reliable is the phase
information and what information can be deduced from
the phase plot (post windowing).
Thanks and Regards
Bharat Pathak
Arithos Designs
www.Arithos.com