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AD9371 Rx FFT spurious

Question asked by RoyG on Jun 7, 2017
Latest reply on Jun 30, 2017 by mhennerich

Hi,

I'm using the ADRV9371 with a ZC706. I'm using the AD 2016_R2 branch of Linux and the HDL as suggested in recent posts. On boot-up I don't see any kernel issues associted with the AD9371/AD9528.  I've generated a profile using the Matlab Profile Generator for AD9371, using the defaults apart from <deviceClock_kHz=122880> as suggested in other posts (profile attached).

 

Currently, we are only interested in using the Rx capability (not TX or RxObs) and I'm using IIO Oscilloscope to understand the device before writing our own software application, but I have an issue with the observed FFT output. I'm using a 30.72MHz reference and injecting a signal (-50dBm) into the Rx1 port at around 400MHz and the Rx LO is set to 400MHz.  When the injected signal is at 400MHz the FFT look OK (attached plot Rx400M.png), but when I move the injected signal away from 400MHz e.g. 410MHz (attached plot Rx410M.png) the FFT shows a large number of spurious.

 

I've also used TES with the AD supplied SD card image and don't see the same problem (the FFT looks OK) for the same injected input signal.

 

Do you know what I'm doing wrong? Many thanks in adavnce for any help.####

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