[USRP-users] XCVR2450 measurements

Jorge Miguel jmiggal at gmail.com
Tue Nov 16 17:24:26 EST 2010


Hello all,

I tested both transmitter and receiver path of XCVR2450 on a USRP2 under
Matlab r2010b. Here some comments about details I found and I don´t
understand.

TX path: (I transmit a 100KHz single tone modulated at 5.5GHz) to a spectrum
analyzer. The expected spectrum is two components at 5.4999GHz and 5.5001GHz

1) Besides the expected spectrum, I can see a powerful (20dB less that the
modulated signal) component at 5.5GHz (Leakage from the MAXIM Local
oscillator?)

2) I see how after 20 or 30 seconds the signal spectrum suddenly (a fast
change) becomes very degraded (a lot of noise in my whole band of interest
appears and the signal is very degraded. The only good news is that the
component at 5.5GHz becomes smaller)

3) From the setting I specify on my USRP TX software I can see about 8KHz
frequency offset in the spectrum analyzer received signal. I connected a
signal generator (a good one) to the same spectrum analyzer and the offset
was 0.2 KHz at the same frequency (5.5GHz). Furthermore there is an
instability over time. (The signal is moving over time around 0.2KHz)

4) How is configured the bandwidth of the TX filters (Of the MAXIM)? (I know
that several values are possible) I wonder that because sometimes when I
change the transmission 5GHz from 5.5 GHz, I get a signal very very weak
that cannot be the case when running again the USRP2.


Can anybody explain some of these issues?

Many thanks,
Jorge.

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