--- In [email protected], "jr_dakota" <[EMAIL PROTECTED]> wrote:
>
> Unless you've discovered a new breakthough in sampling, you need a
> sampling rate at least twice the highest frequency you want to
sample,
> hence a 44.1K sampling rate on CD's covers only 20Khz of frequency
> resolution, same with the 48Khz sampling rate of DATs ... the extra
> 4.1Khz or 8Khz in the case of DAT and souncards is a guard
frequency
> ... sure you are sampling two channels but in an IQ setup the
second
> channel is same frequencies shifted by 90 degrees ... so at a 48Khz
> sample rate the very best I can get is 24Khz and even that is
pushing
> right up to the Nyquist frequency (Sample rate diveded by 2)
>
...........
>
> Am I missing something here?
>
This is true for a real signal, but in this case you are sampling a
complex signal.
You are sampling the same signal 2 times which is equivalent to
sample it at twice the frequency.
Or another way: having the I & Q channels alows you to know if the
signal is USB or LSB, sampling at 48KHz for example gives you a
bandwidth of 24 KHz for USB but also for LSB -> equivalent to 48KHz.
Jean-Claude PJ2BVU
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