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From: | Kyle Zhou |
Subject: | [Discuss-gnuradio] wbx usrp1 sampling spectrum distortion |
Date: | Tue, 20 Apr 2010 19:51:27 +1000 |
User-agent: | Thunderbird 2.0.0.24 (Windows/20100228) |
HiI use WBX + USRP1 to capture a DAB+ digital radio broadcast signal at frequency 204.64MHz and bandwidth 1.4MHz.
Sampling rate is 2Msps (decimation=32)The spectrum shown by usrp_fft.py is normal and clean. However, after capturing the data using usrp_rx_cfile.py and loading the data to Matlab and show the spectrum, I found an unexpected portion of spectrum around the Nyquist frequency (1MHz in this case). The parameters I use for usrp_rx_cfile and usrp_fft are the same: -f 204.64M -d 32 -g 6.
I uploaded a snapshot of the spectrum: http://lh4.ggpht.com/_ozkfEhDY6Mg/S81p3QihHkI/AAAAAAAAAsE/KJ8vtRo4EI4/spec_samp.jpgI can filter out the undesired part easily but that cost computational resource and I do want to find out the cause.
Regards Kyle
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