Originally Posted by Lavry Tech
I contacted Dan and asked him to take a look at the on-going discussion. He is busy with new designs; but took a minute to address the question of how many samples are required for good results:......snip.....
Thanks for getting back.
Perhaps I should re-phrase the question.
In the paper, it is alluded that by temporally shifting the sampling times for the same waveform, reconstruction will produce the exact same waveform. If the reconstruction is a simple one sample only S/H followed by a brickwall, I question the equivalence in both amplitude and phase. . It is a simple thought exercise which should confirm/deny part of this.
Sample a one volt 1khz sine at 4khz. Sample the sine at 0 degrees, 90, 180, and 270. The data series will be 0, 1, 0, -1. Now, sample it at 45, 135, 225, and 315 degrees. The data series is now .7071, .7071, -.7071, -.7071. Using a simple S/H, these two data streams will clearly produce a different pattern which is put into the brickwall. The first is quarter milllisecond wide +/- rectangles of amplitude 1, the second is a half millisecond square wave, +/- .7071 amplitude. Clearly the energy in the signal remains the same (1 squared (1) times .25 = .25, and .7071 squared (.5) times .5 = .25, so the amplitude will be identical through a brickwall despite a clearly different input signal waveform.. allaying my first concern of amplitude...
My question is phase. Will this system preserve phase, more specifically, interchannel timing relationships, if two 5 or 10 Khz sines are simultaneously A/D'd, then Dac'd/filtered, where the two signals are temporally shifted from 0 to say 250 uSEc in steps of 5uSec.
I would scope the input and measure zero crossing difference, then output for same. Graphing source delay vs output delay should produce a straight line. The question is, does it?
Edited by jnjn - 5/18/12 at 6:31am