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 (<
usrp-users@lists.ettus.com>) 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...
>
>
>
>
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