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AD9361 noise

Question asked by MarkusH on Jul 8, 2017
Latest reply on Jul 10, 2017 by mhennerich



we are using on a custom made PCB two AD9361 with a MicroZed board. For my opinion we see in our setup a to high noise level. Attached there is a screen-shot of IQ data without any signal (from 2800 to 3100) at the Input. 

Settings of the AD9361 are:


cat /sys/bus/iio/devices/iio\:device1/*rates*
BBPLL:1024000000 ADC:64000000 R2:32000000 R1:16000000 RF:8000000 RXSAMP:8000000
BBPLL:1024000000 DAC:64000000 T2:32000000 T1:16000000 TF:8000000 TXSAMP:8000000


The RX gain is 60dB and the frequency is 866.5MHz


So the idea was to use the FIR filter with some decimation to reduce the noise. I designed a filter with the "MATLAB Filter Design Wizard for AD9361" with the following amplitude and phase response.



Settings of the AD9361 are:

cat /sys/bus/iio/devices/iio\:device1/*rates*
BBPLL:1024000000 ADC:256000000 R2:128000000 R1:64000000 RF:32000000 RXSAMP:8000000
BBPLL:1024000000 DAC:256000000 T2:128000000 T1:64000000 TF:32000000 TXSAMP:8000000


Enabling the filter, reduces the high frequency pats of the noise, but the amplitudes are not dropping significantly.



What I have to do to get a lower noise level?




Regards, Markus