Non-linearity testing Algorithm
The heart of the co-testing of the DAC-ADC pair is the algorithm that will be able to decipher which non-linearities comes from which component under test. Although the development and verification are not directly a part of this project, it seems useful to give a basis to the algorithm. The algorithm is made possible by running a nonlinear source, or nonlinear DAC, through two different filters and then digitizing the signal with a nonlinear ADC. The non-linearities from the source will be attenuated differently with the filters, but will gain the same nonlinearities from the ADC. Therefore the differences in the two output signals can be contributed solely to the difference in the filter’s attenuation of the source’s non-linearities. By knowing the transfer function of the filters, it is possible to retrieve the non-linearities of each device under test individually. The block diagram of this process can be seen below as well as described more thoroughly in the attached PowerPoint.
| adc_nonlinearity_testing_algorithm.pdf |