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IIO Oscilloscope Distortion

Question asked by htorke on Apr 25, 2017
Latest reply on Apr 28, 2017 by mhennerich

We are seeing inconsistent output between the Evaluation Software branch and the IIO Oscilloscope branch of the AD9371 example designs.


When attempting to transmit a pulsed square wave using IIO Oscilloscope, this is the output we are seeing:


While the general pulse shape seems to be accurate, zooming in reveals additional distortions that should not be present


The local oscillator is accurate in frequency, and can be changed at will, so there are no problems with that. The issue seems to be with how the 9371 is handling direct IQ output.


Conversely, when using the same IQ data loaded into the Evaluation Software, this is the output:


The waveform is a clean pulse with no distortions.


It seems that the control lines are functioning properly, and the hardware is capable of transmitting appropriately, based on the TES output, so I imagine either a difference in the PL logic of the IIOscope platform or a difference in software is causing the distorted output.


For reference, we are using the most recent TES release and the December 2016 release of the IIO Oscilloscope image, without making any changes to the board/software.


What would be the cause of these distortions on the TX output?