TX characterisation of USRPN210 with SBX daughterboard

Hi,

I am trying to characterize the TX and RX characteristics of USRPN210
with a
SBX board.
I have tried one test : Amplitude Variation effects, by varying the
amplitude in steps and finding out the o/p power through spectrum
analyser.
The foll are the readings I got.
Amplitude level 921.25 MHz 2.45625 GHz
0.0625 -49.18 -60.97
0.125 -43.2 -55.05
0.25 -37.25 -49.09
0.5 -31.24 -43.05
1 -25.38 -37.13
Amplitude change 921MHz 2.456GHz
1 to 0.5 5.86 5.92
0.5 to 0.25 6.01 6.04
0.25 to 0.125 5.95 5.96
0.125 to 0.0625 5.98 5.92

when i ploted the graph in excel, (O/p power Vs amplitude), i got two
almost
linear curves, but their was a big difference in the 2 lines @ 921.25
MHz
and 2.45625 GHz (as seen above) at the start and if extrapolated could
converge at a higher ampl and o/p power.
I was not sure about my results and was looking to see if some one could
let
me know if these values look within the normal expected behaviour? if
not,
please let me know what is the normal expected behaviour.
I am new to USRP and GRC programming and doing this for a project.
http://gnuradio.4.n7.nabble.com/file/n47157/Oppower_vs_ampli.png

Thanks in advance


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On 03/24/2014 05:56 AM, Gayathri Ramasubramanian wrote:

I am trying to characterize the TX and RX characteristics of USRPN210
with a SBX board. I have tried one test : Amplitude Variation
effects, by varying the amplitude in steps and finding out the o/p
power through spectrum analyser. The foll are the readings I got.
Amplitude level 921.25 MHz 2.45625 GHz 0.0625 -49.18 -60.97 0.125
-43.2 -55.05 0.25 -37.25 -49.09 0.5 -31.24 -43.05 1 -25.38 -37.13
Amplitude change 921MHz 2.456GHz 1 to 0.5 5.86 5.92 0.5 to 0.25 6.01
6.04 0.25 to 0.125 5.95 5.96 0.125 to 0.0625 5.98 5.92

Gayathri,

how did you measure? Did you use an antenna, or cable connection to the
spectrum analyzer?
Also, what were your gain settings? And your tx signal?

Martin

Hi Martin

Thanks for looking into my post.
I used a cable to connect to the spectrum analyzer ( united microflex
150
with 15 db/ft attenuation, my cable length was 1 ft). However before
connecting to the spectrum analyzer, I had an attenuator set to 50 dB.
These readings were taken with a gain set to zero. I used
tx_waveformsprogram provided in the examples with:
BB freq: 6.25MHz
Sampling rate : 13 MHz
I just varied my amplitude in these steps.

Thanks
Gayathri

On Mar 24, 2014, at 11:22 AM, “Martin B.-2 [via GnuRadio]” <
[email protected]> wrote:

On 03/24/2014 05:56 AM, Gayathri Ramasubramanian wrote:

I am trying to characterize the TX and RX characteristics of USRPN210
with a SBX board. I have tried one test : Amplitude Variation
effects, by varying the amplitude in steps and finding out the o/p
power through spectrum analyser. The foll are the readings I got.
Amplitude level 921.25 MHz 2.45625 GHz 0.0625 -49.18 -60.97 0.125
-43.2 -55.05 0.25 -37.25 -49.09 0.5 -31.24 -43.05 1 -25.38 -37.13
Amplitude change 921MHz 2.456GHz 1 to 0.5 5.86 5.92 0.5 to 0.25 6.01
6.04 0.25 to 0.125 5.95 5.96 0.125 to 0.0625 5.98 5.92

Gayathri,

how did you measure? Did you use an antenna, or cable connection to the
spectrum analyzer?
Also, what were your gain settings? And your tx signal?

Martin

when i ploted the graph in excel, (O/p power Vs amplitude), i got two
almost linear curves, but their was a big difference in the 2 lines @
921.25 MHz and 2.45625 GHz (as seen above) at the start and if
extrapolated could converge at a higher ampl and o/p power. I was not
sure about my results and was looking to see if some one could let me
know if these values look within the normal expected behaviour? if
not, please let me know what is the normal expected behaviour. I am
new to USRP and GRC programming and doing this for a project.


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The graph doesn’t match your numbers.

Ron

On 03/24/2014 05:44 PM, Gayathri Ramasubramanian wrote:

Thanks for looking into my post.
I used a cable to connect to the spectrum analyzer ( united microflex
150 with 15 db/ft attenuation, my cable length was 1 ft). However before
connecting to the spectrum analyzer, I had an attenuator set to 50 dB.
These readings were taken with a gain set to zero. I used tx_waveforms
program provided in the examples with:
BB freq: 6.25MHz
Sampling rate : 13 MHz

BTW, that’s an unusual sampling rate… are you running off of your own
clock?
Still, the differences are pretty big. I’m not surprised to see less for
the higher frequency, but the magnitude does surprise me.

I just varied my amplitude in these steps.

Can you play around with the gain (say, set it to mid-point in dB) and
see if the differences are still that big?

M

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