[USRP-users] Signal harmonics in WBX output

Daniele Nicolodi daniele at grinta.net
Fri Oct 31 07:43:56 EDT 2014


On 30/10/14 18:15, Daniele Nicolodi via USRP-users wrote:
> The real trouble comes when in this configuration I increase the gain
> above 20 dB: also the 80 MHz carrier starts to be amplitude modulated ad
> frequency x. Of course this is not what I would like to see :)

The modulation is there also for gains lower than 20 dB, just its
amplitude is much smaller and it increases non linearly with the gain
for gains above 20 dB.

I understood its origin!  It comes from amplitude imbalance between the
I and Q mixers, and I found that you are supposed to calibrate that.
I'll be playing with the calibration now, to see how well this can be
cancelled.

The questions about the large harmonics I measure are still standing,
but I suspect that they are normal and expected. However I would really
like some explanation about the "mode_n=integer" parameter and when it
is useful.

Cheers,
Daniele






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