Re: [LAD] Determining Phase

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To: <linux-audio-dev@...>
Date: Monday, June 27, 2011 - 12:50 am

On the subject of the word Quadrature:

The word Quadrature is shorthand for the imaginary component of a
complex-valued variable. Furthermore, it is almost exclusively used in
the domain of carrier modulated waveforms. The word for the real
component is In-Phase. That is why so many texts on the subject use I
and Q to describe these two concepts. This choice of words was due to
the fact that some radiomen in the '20s created a 90-degree delayed
signal from the carrier (a quatrature relationship with respect to the
carrier in the ancient college trigonometry literature) and (I doubt
ignorantly) left out the fact that it was simply a practical way to
perform complex analysis on a narrow-band waveform.

@Gene:
It was unfortunate that you used the mathematically reserved word
complex to describe a complicated signal. The concept of quadrature in
an audio baseband signal assumes a single frequency, say 1000 Hz.,
wherein that arbitrarily chosen "carrier" is assumed for Quadrature
analysis. In fact, the Fourier Transform assumes an infinite number of
such carriers to create a continuous, complex-valued transform of the
pure real audio channel. The FFT is a Discrete Fourier Transform that
periodizes the waveform to create a finite number of discrete carriers,
each at the bin related to the length of the transform. Each bin of
frequency output by that transform has a real and an imaginary component
-- Quadrature.

@Gordon, please remember that your SDAR code ASSUMES the carrier
frequency so as to be able to analyze Quadrature. It is a more
complicated concept in general complex analysis of a broadband signal
such as audio.

Duncan
-- In the limit as productivity approaches infinity all jobs become
entertainment or neurosis.

On 06/26/2011 05:02 PM, Gordon JC Pearce wrote:

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Messages in current thread:
[LAD] Determining Phase, , (Sat Jun 25, 2:29 pm)
Re: [LAD] Determining Phase, Gordon JC Pearce, (Sun Jun 26, 3:24 pm)
Re: [LAD] Determining Phase, gene heskett, (Sun Jun 26, 6:54 pm)
Re: [LAD] Determining Phase, Gordon JC Pearce, (Sun Jun 26, 10:01 pm)
Re: [LAD] Determining Phase, Duncan Gray, (Mon Jun 27, 12:50 am)
Re: [LAD] Determining Phase, Fons Adriaensen, (Sun Jun 26, 8:08 pm)
Re: [LAD] Determining Phase, Duncan Gray, (Sun Jun 26, 3:14 am)
Re: [LAD] Determining Phase, , (Sun Jun 26, 8:56 am)
Re: [LAD] Determining Phase, Jörn Nettingsmeier, (Sun Jun 26, 9:58 am)
Re: [LAD] Determining Phase, Arnold Krille, (Sun Jun 26, 3:47 pm)
Re: [LAD] Determining Phase, Jörn Nettingsmeier, (Sun Jun 26, 4:06 pm)
Re: [LAD] Determining Phase, Arnold Krille, (Sun Jun 26, 4:24 pm)
Re: [LAD] Determining Phase, Rui Nuno Capela, (Sat Jun 25, 10:40 pm)
Re: [LAD] Determining Phase, , (Sun Jun 26, 9:19 am)
Re: [LAD] Determining Phase, Rui Nuno Capela, (Sun Jun 26, 4:36 pm)
Re: [LAD] Determining Phase, Fons Adriaensen, (Sat Jun 25, 7:30 pm)
Re: [LAD] Determining Phase, Gabriel M. Beddingfield, (Sat Jun 25, 6:55 pm)
Re: [LAD] Determining Phase, Fons Adriaensen, (Sat Jun 25, 7:49 pm)
Re: [LAD] Determining Phase, Emanuel Rumpf, (Sat Jun 25, 10:04 pm)
Re: [LAD] Determining Phase, Gabriel M. Beddingfield, (Sat Jun 25, 10:44 pm)
Re: [LAD] Determining Phase, Emanuel Rumpf, (Sat Jun 25, 11:27 pm)
Re: [LAD] Determining Phase, Emanuel Rumpf, (Sat Jun 25, 10:30 pm)
Re: [LAD] Determining Phase, Jörn Nettingsmeier, (Sat Jun 25, 10:23 pm)
Re: [LAD] Determining Phase, Fons Adriaensen, (Sun Jun 26, 2:17 am)
Re: [LAD] Determining Phase, Jörn Nettingsmeier, (Sun Jun 26, 9:43 am)
Re: [LAD] Determining Phase, Fons Adriaensen, (Sun Jun 26, 11:26 am)
Re: [LAD] Determining Phase, , (Sun Jun 26, 8:50 am)
Re: [LAD] Determining Phase, Fons Adriaensen, (Sun Jun 26, 12:56 pm)
Re: [LAD] Determining Phase, Erik de Castro Lopo, (Sun Jun 26, 10:27 am)
Re: [LAD] Determining Phase, , (Mon Jun 27, 12:41 pm)
Re: [LAD] Determining Phase, Fons Adriaensen, (Mon Jun 27, 8:16 pm)
Re: [LAD] Determining Phase, Fons Adriaensen, (Mon Jun 27, 8:19 pm)
Re: [LAD] Determining Phase, Jörn Nettingsmeier, (Mon Jun 27, 1:14 pm)
Re: [LAD] Determining Phase, Folderol, (Sat Jun 25, 10:35 pm)
Re: [LAD] Determining Phase, Gabriel M. Beddingfield, (Sat Jun 25, 9:33 pm)
Re: [LAD] Determining Phase, Jörn Nettingsmeier, (Sat Jun 25, 3:57 pm)