Re: TX characterisation of USRPN210 with SBX daughterboard

Hi Ron

Sorry about that. Please find attached the modified graph.
The two curves seems more consistent in this graph.
I am assuming the DAC should have reached saturation at Ampl =1. However
my
reading don’t seem to depict that so well.
Would it have been better to started at such lower values of Amplitude?
I understand for a SBX board, the Tx’d o/p power range is +16 -20 dbm (
1.5
to 2.2 V) with a 32 dB gain control range, which I understand that I can
vary the Tx’d power from -16 dBm to +16 dBm (0.035 V ~ 1.5 V). Is my
understanding correct?. So should I vary my ampltude from 0.035 V untl
1.5
V? is that within the usrpN210’s working levels?

Thanks

On Mon, Mar 24, 2014 at 3:48 PM, Ron E. [via GnuRadio] <
[email protected]> wrote:

SBX board.
Amplitude change 921MHz 2.456GHz
converge at a higher ampl and o/p power.

http://gnuradio.4.n7.nabble.com/TX-characterisation-of-USRPN210-with-SBX-daughterboard-tp47157p47165.html

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Tx_waveforms_plot1.PNG (32K)
http://gnuradio.4.n7.nabble.com/attachment/47168/0/Tx_waveforms_plot1.PNG

I took a look at the SBX schematic. The final output
uses a Mini-Circuits PHA-1+ MMIC amplifier that’s
rated at +22 dBm output power at 1 dB compression.

It would seem that the gain distribution of the SBX
is arranged so that the PHA-1+ cannot be overdriven,
even at DAC full-scale and 0 dB attenuation. That is,
you cannot saturate the SBX.

So your measurements are showing that the SBX is
quite linear over it’s operating range.

BTW, I’m not really familiar with the USRP (I’m a bladeRF
user), but the amplitude value in tx_waveforms is most
likely just a relative amplitude (with 1 equal to DAC
full-scale), and not an actual voltage.

Ron

Ron,

thanks for the input!

On 03/25/2014 12:02 PM, Ron E. wrote:

quite linear over it’s operating range.

BTW, I’m not really familiar with the USRP (I’m a bladeRF
user), but the amplitude value in tx_waveforms is most
likely just a relative amplitude (with 1 equal to DAC
full-scale), and not an actual voltage.

That is correct. If you were using GNU Radio, and connected that to a
USRP, this would be amplitude of the digital signal going into the USRP
sink.

Martin

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