On Mon, Nov 30, 2009 at 07:53:11PM -0600, neha kochar wrote: > (i) I saw the option of digital amplitude in benchmark_tx.py. Could someone > tell me the gain of which component on the USRP board is controlled by this > digital amplitude.
None is. Have a closer look at transmit_path.py, and you'll see this controls the signal level before the ADC. When you set amp == 1, the full ADC scale will be used -- however, this will also cause the saturation effects (when you run the ADC at full scale, you will get spurious signals, which is why you should back off a bit). I guess that also explains the rest... Cheerio MB > (ii) Also I tried to connect two USRP1 in a wired fashion and put one to > transmit using benchamrk_tx.py and the other to receive using benchmark_rx.py > with the default gain of 45. I noticed that at digital amplitudes (at the > transmitter) of 0.64 to 1, the BER suddenly increases inspite of wired > connection. At values 0.63 and below, the bit errors are zero as expected. I > was wondering if someone could explain this behaviour. > > > (iii) In addition, I measured power levels at each digital amplitude in > increments of 0.1 (i.e. 0.1, 0.2, 0.3, ....., 1) and I observed the following > values using a spectrum analyzer: > > > Digital Amp Power(dBm) > > > 0.1 -8 to -4 > 0.2 -2 to 2 > 0.3 1 to 5 > 0.4 4 to 7 > 0.5 5 to 8 > 0.6 5 to 9 > 0.7 6 to 10 > 0.8 7 to 9 > 0.9 8 to 11 > 1 8 to 11 > > > As can be seen, > at larger > digital > amplitudes, > there is not > much difference > in power levels > between > adjacent values > of digital > amplitudes. It > seems like > something at > the transmitter > is saturating, > not allowing > more than a > particular > amount of power > to be > transmitted. > Could someone > please > elaborate on > this behaviour > and its > reasons? > > > Thanks in > advance. > > > Regards, > > Neha. > > _______________________________________________ > Discuss-gnuradio mailing list > [email protected] > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio -- Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin Braun Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-3790 Fax: +49 721 608-6071 www.cel.kit.edu KIT -- University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association
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