On Feb 19, 2020, at 1:54 PM, Alvaro Pendas <[email protected]
<mailto:[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]
<mailto:[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...
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