Indeed. You’d have to use an external calibration source at several places over your parameter space (frequency gain sample rate)
Sent from my iPhone > On Feb 19, 2020, at 1:54 PM, Alvaro Pendas <[email protected]> wrote: > > > Marcus thank your for your answer, > > First of all, you are right, the range is -1 to 1 (instead of 0 to 1 as I > said before). So, for example, in the receiving part, the values you get out > of the UHD Source have a linear relationship with the voltage of the analog > signal, but I understand there is no easy way to calculate that level with > the only information of the GNU Radio samples. Is that correct? > >> El mié., 19 feb. 2020 a las 19:22, Marcus D. Leech via USRP-users >> (<[email protected]>) escribió: >> On 02/19/2020 12:01 PM, Alvaro Pendas via USRP-users wrote: >> > Hello, >> > I am using GNU Radio and the USRP B200. I have noticed that for the >> > GNU block UHD: USRP Sink, the values you pass to the block must be in >> > the range 0 to 1. I guess that means if you do not want to lose >> > resolution you must ensure that you use the full range, that is to >> > say, your minimum is 0 or close to 0, and your max is 1 or close to 1. >> > Am I correct? >> > >> > On the other hand, what are the meaning of the values produce by the >> > block UHD: USRP Source? They must be related to the signal power, but >> > I am not sure about their range. Is the minimum value that block can >> > produce the min of the ADC output, and the max, the max of the ADC >> > output? With the USRP B200 the ADC resolution is 12 bits, are the min >> > and the max always set with the same value, or does it depend on the >> > USRP configuration? >> > >> > I am using GNU Radio right now, but probably, just knowing how this >> > works with UHD would be enough to understand the rest. >> > >> > Thank you for your time, >> > >> > Alvaro >> > >> Gnu radio generally likes to have baesband data streams scaled into >> {-1.0,+1.0} which are linearly related to instantaneous voltages at >> the antenna of the hardware. >> >> To a first approximation, a value near +1.0 or -1.0 will drive the ADC >> to its maximum +/- value. But that's only an approximation, since the >> signal is processed a fair amount (linearly) prior to reaching the >> ADC/DAC, and with analog hardware there's no way of ensuring that >> a max value wont' over-drive the analog hardware. >> >> Power of a sinusoidal signal is proportional to the I*I + Q*Q -- >> remember we're dealing with *voltages* here, so ohms law applies... >> >> >> >> >> _______________________________________________ >> USRP-users mailing list >> [email protected] >> http://lists.ettus.com/mailman/listinfo/usrp-users_lists.ettus.com
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