ADC32RF80: Why data truncation can produce a DC spur in noise floor?

user5959213

Part Number: ADC32RF80

Hi all,

We know the ADC32RF80 is a 14bit IC,but the fpga has trunccated the14bit data that received from the ADC output to 12bit for power calibraion.We see there is a large dc in the center of the spetrum when FFT analyse the noise floor of the adc output.

over 3 years ago

0 Kang Hsia over 3 years ago

TI__Guru 74619 points

Hi,

Truncation cuts off the LSBs without rebalancing the bits. This by default create a DC offset because you are basically adding signals to make the last 2 LSBs to go to zero. This is the reason for the DC offset.

You will need to perform rounding process to more accurate remove the two LSBs while minimizing DC offset.

There are many discussions on various DSP topic sites like below

https://www.dsprelated.com/showthread/comp.dsp/73634-1.php

RF & microwave

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ADC32RF80: Why data truncation can produce a DC spur in noise floor?