Guys, I managed another comparison test last night. http://zoolu.co.kr/episodes/6
*. Test tone signal quality I used a siggen as good as I could get. :-) According to the spectrum analyzer, it seemed that the siggen did not generate any noticeable harmonics(1st and 2nd pictures). Actually, I raised the power level up to 0 dBm when I tested last night. But took the snapshots with -34dBm level. *. Signal level I reduced the signal level down to -34dBm just to avoid any possible input level saturation. I believe it is low enough. :-) My questions 1. Still get spurs As you can see in 3rd and 4th pictures, I still have quite significant spurs in band. However, when I match the local oscillator frequency with that of test signal like picture #5, all spurs were gone away. So, I am still suspicious if those spurs came out of the LO leakage from the FPGA CORDIC. (I don't believe that happens in the digital domain. Probably, the digital switching noise spilled over to the analog part and it was fed to ADC input. That's my best guess.) Is there any comments, corrections, or suggestions? I probably have to figure out Kyle Pearson's work on rounding in FPGA that Frank mentioned before. 2. Automatic signal level scaling I made comparison between different FFT sizes and the peak level varied. As you can see, The Peak level was -11dB with FFT size of 8192 and -19dB with 1024 while the absolute signal power level was -34dBm. The differences are about 8 dB and it explains because the FFT size scale is 8(=2^3) times. Which part of the code does the automatic scaling? Ilkyoung. _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
