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[Discuss-gnuradio] Large spurious in data obtained from USRP2+DBSRX


From: Thomas Hobiger
Subject: [Discuss-gnuradio] Large spurious in data obtained from USRP2+DBSRX
Date: Fri, 15 Oct 2010 18:21:12 +0900
User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.12) Gecko/20100907 Fedora/3.0.7-1.fc12 Mnenhy/0.8.3 Thunderbird/3.0.7

Hi all,

I am implementing a GPS receiver based on the USRP2 with a DBSRX daughterboard equipped, whereas the software is only using the URSP2 C++ interface, the rest is done without GNURADIO. The receiver works quite well, but I noticed that whatever I do I get really huge spurious signals in the obtained spectra. In order to make clear what I mean, I am attaching a plot of direct sampling at 1.0 GHz with a decimation of 4 and gain=1. There is no signal going in the URSP2 so what you should see is something like instrumental noise. Nevertheless, there are these huge spurious signals. These spurious signals don't change their amplitude nor their relative position w.r.t. the center frequency independent of which RF I choose.

Is this a problem of the DBSRX or is it related to the FPGA, firmware, etc?

Any comments highly appreciated.

Best regards,
  Thomas Hobiger


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Dr. Thomas Hobiger
Space-Time Measurement Project
Space-Time Standards Group
New Generation Network Research Center
National Institute of Information and Communications Technology
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Attachment: spurious.jpg
Description: JPEG image


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