discuss-gnuradio
[Top][All Lists]
Advanced

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Discuss-gnuradio] Basic sampling frequency question


From: Colby Boyer
Subject: Re: [Discuss-gnuradio] Basic sampling frequency question
Date: Mon, 27 Jun 2011 12:28:10 -0700

On Mon, Jun 27, 2011 at 11:02 AM, Tom Hendrick <address@hidden> wrote:
I have a really simple question that I can't seem to find the answer to online (and pardon my limited signal processing background). I'm trying to help a fellow colleague figure out a processing problem.

An external code modulates a real-valued signal that is eventually fed into GRC.  For now the signal is generated with some arbitrary positive center frequency and then a GRC script converts it to complex and then downshifts and centers it at 0Hz.  This isn't efficient because the modulation in the external code takes a lot longer with higher sampling frequency.

If the external code was modified to put the real-valued signal in the -5 to 5kHz band (centered at 0Hz and assuming a real-valued signal can represent negative frequencies), is the minimum sampling frequency to avoid aliasing 20kHz or is it 10kHz?   This is before the GRC script converts it to complex. 

Thank you in advance.. Tom



_______________________________________________
Discuss-gnuradio mailing list
address@hidden
https://lists.gnu.org/mailman/listinfo/discuss-gnuradio



A few things:

* A real valued signal has a frequency spectrum that is symmetric around 0Hz. So the negative frequency components are identical to the positive frequency components.

* For your case, the minimum sampling frequency would be 10KHz. The signal being real or complex does not make a difference. If a signal occupies frequency -F to F at the baseband (centered), your Nyquist sampling rate is 2F.

Hope this helps,

Colby

reply via email to

[Prev in Thread] Current Thread [Next in Thread]