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So, real question about digitizing 15 kHz
On Sun, 23 Nov 2003 04:11:24 GMT, (Scott Gardner)
wrote:
On Sat, 22 Nov 2003 21:07:24 -0500, "Arny Krueger"
wrote:
"ScottW" wrote in message
news:AmUvb.4608$ML6.2599@fed1read01
"Erik Squires" wrote in message
ervers.com...
So, here's my question. If I digitize a 15 kHz signal, using a 44.1
kHz sampling rate, I'm going to get about 3 samples / cycle.
Are the normal digital filters good enough to reproduce a 15 kHz
singal with varying amplitude?
Deconstruct this signal to frequency domain and it won't be a pure
15 kHz.
Wrong.
There has to be another component imposed on the 15 kHz that "varies the
amplitude".
Wrong.
Three samples is sufficient to define a sine wave that has unique frequency,
phase and amplitude. In fact, just slightly more than two samples is
sufficient.
Arny,
I am probably looking at this the wrong way, using an
oversimplified model, but I can't see how a sine wave can be
completely defined by three points.
A pure sine wave has infinite length which is more than three points
in total. This makes a difference.
I'm picturing a sine wave plotted with time along the x-axis,
and amplitude along the y-axis. If I tell you that the amplitudes at
zero seconds, 1 second, and 2 seconds are all zero, I've given you
three different points along the wave. From this, the period can be
measured and the frequency derived from that, but I don't see how I've
given you enough information to calculate the amplitude.
Let me know what I'm missing. Do the three points have to
have non-zero amplitude for them to be used to define the waveform?
Thanks,
Scott Gardner
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