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Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion
From: |
Marcus D. Leech |
Subject: |
Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion |
Date: |
Thu, 04 Nov 2010 01:11:39 -0400 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.12) Gecko/20100907 Fedora/3.0.7-1.fc12 Thunderbird/3.0.7 |
On 11/04/2010 01:02 AM, Steve Mcmahon wrote:
> Marcus:
>
> Thank you for your reply. Let me ask you another question to make sure I'm
> understanding this correctly. Remember, I have a USRP2 board with a WBX
> daughterboard. If I construct a flow graph where a signal source block
> generates a 7 khz cosine at a sample rate of 200 khz (100e6/500), and if this
> cosine is fed into a USRP2 sink block with its "frequency" parameter set to
> "900M", then will I see a spike in the WBX output spectrum at 907 MHz, or at
> 893 MHz, or both? (assuming perfect precision of the internal reference clock
> on the USRP2) What if it were a sine instead of a cosine? Thanks again for
> your help. I really appreciate your time.
>
> Steve McMahon
>
You'll see a spectral spike at 900.007Mhz. Regardless of the phase.
You keep making the
"907MHz" mistake in your posts. Remember that upconversion doesn't
"expand" the frequency
components. So a spectral component at 7Khz will still be at 7Khz
relative to the upconverted
"DC" frequency.
Your complex baseband signal has spectral components that stretch from
-bandwidth/2 to
+bandwidth/2. If you have a component at +7KHz, it'll still be at
<upconverted-frequency>+7Khz
when it's finished being upconverted.
Interpolation also doesn't change the relative spacing of spectral
components, only the time-domain
resolution of the samples of those spectral components. So your +7Khz
signal sampled at
200KHz will still be at +7Khz when sampled at 100MHz.
--
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, (continued)
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Marcus D. Leech, 2010/11/03
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Dan Harasty, 2010/11/03
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Markus Heller M.A. (relix GmbH), 2010/11/03
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Marcus D. Leech, 2010/11/03
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Markus Heller M.A. (relix GmbH), 2010/11/03
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Marcus D. Leech, 2010/11/03
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Markus Heller M.A. (relix GmbH), 2010/11/04
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Marcus D. Leech, 2010/11/03
Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, alexander levedahl, 2010/11/03
Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion, Steve Mcmahon, 2010/11/04
- Re: [Discuss-gnuradio] questions about USRP2 sink block and upconversion,
Marcus D. Leech <=