Re: [Discuss-gnuradio] phase noise of RFX900 daughter board

[Marcus Müller]

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Hi Pengyu,

could you elaborate on your measurement procedure? What did you send
on tx? 46dB attenuation does make sense in a output to input
configuration, yet it is "only" about 30dB stronger than what I'd
expect of crosstalk. Also: Did you use or bypass the SAW filters?
What are the units on your graphs? An average amplitude of 3700 looks
strange to me for such a measurement...
also: scale! You're using 250px for 1e6 samples, that's 4000 samples
per pixel, so if there was but a single sample that would have a high
phase deviation, it would look the same as if all of the 4000 samples
were phase jumping unceasingly. Anyway, your constellation diagram
looks relevant, it shows the typical rotational widening of a
constellation point that would appear in a communication receiver due
to channel influences, inperfect synchronization and phase jitter.
Maybe you should share the software you used to measure this, so that
we can get a better understanding of what's happening :)

Greetings,
Marcus


On 10.02.2014 23:18, Pengyu Zhang wrote:
> Hi,
> 
> We have tried to measure the phase noise of RFX900 daughter board
> when the daughter board is mounted on a USRP 1 mother board. When
> we directly connect the TX/RX port to the RX2 port through a 46dB
> attenuation signal, we still observe significant amount of phase
> noise as shown in the attached figures. Those figures suggest that
> the phase noise is about 8 degrees which cannot be tolerated by
> many communication systems. Would be great if you guys can provide
> some suggestions on reducing the phase of the USRP platform.
> 
> Pengyu
> 
> [image: Inline image 1]
> 
> [image: Inline image 2]
> 
> [image: Inline image 3]
> 
> 
> 
> _______________________________________________ Discuss-gnuradio
> mailing list address@hidden 
> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
> 
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