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AD9361 Tx filter chain bit growth/data scaling

Question asked by obenj on Jul 20, 2015
Latest reply on Jul 21, 2015 by obenj

Is there information available for the management of bit growth in the AD9361 Tx filter chain? I'm having issues with distortion due to digital overflow in the filter chain. I'm attempting to maximize signal power without distortion.

 

I have a number of different FIR coefficient files generated from the Filter Wizard utility that have different levels of gain. Because of this when I use near-full-scale tone as input data, I see distortion at different levels of gain in my input data. There is roughly a bit and a half (~9dB) difference between some of these levels.

 

I was hoping that knowing the FIR, HBx, INT digital filter scaling could help me pre-calculate the necessary scaling of my input data and FIR coefficients to utilize the DAC's 12-bit dynamic range and avoid digital overflow.

 

Thanks.

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