FPGA Central

[email protected] (praveen) wrote in message news:<[email protected] com>...
> Hello,
> I have a signal consisting of 4 harmonics (200k,400k,600k,and 800k Hz)
> and dc component.The signal is very pure and SNR better than 60 dB. I
> have to sample it in sub Nyquisit rate(lesser than 1600k). What
> sampling rate should i choose so that there no alaising. I cannot
> chose higher sampling rate because of my hardware constraints.
>
>
> waiting for reply
> regards
> praveen

As has been said in this thread you cannot sample below 1600kHz
without aliasing but if the signal is, as you suggested, a periodic
signal, then if your aim is to merely reconstruct the wave shape for
the signal you can do it "with aliasing". Do a search for aliasing
oscilloscope and see what you find.

You should sample at a frequency close to the fundamental of the
waveform (ie 200kHz). The resulting output signal will have a
fundamental equal to the difference between the two. Aliasing can be
exploited when you know the signal you're analysing is periodic. This
method is used in very fast oscilloscopes to visualise signals that
current technology can not capture us the normal sampling approach.

Regards,


Paavo Jumppanen,
Author of AtSpec : A 2 channel PC based FFT spectrum analyzer
http://www.taquis.com