Abstract
The accuracy of AD conversion can be improved usin g the post-correction of digitizer non-linearity. In principle two methods could be applied – look-up table or an analytical inverse function of integral non-linearity curve (INL(n)). Look-up table can be easily implemented but it demands huge memory space particularly for high resolution ADCs. Inverse function offers flexible solution for parameterization (e.g. frequency dependence) but it also requires fast DSP for real-time correction. The data or coefficients for bot h methods are frequently determined from a histogram of acquired pure sinusoidal signal. Non-linearity curve can also be gained by another procedure demanding significantly less samples – approximation from a frequency spectrum. The correction of ADC nonlinearity by means of inverse function of INL(n) curve is analyzed in this paper and the results are presented.
Highlights
Non-linearity curve can be gained by another procedure demanding significantly less samples – approximation from a frequency spectrum
The ADC non-linearity is inherently described by the Integral Non-linearity curve INL(n) which is defined as the difference of ADC output and input as the function of the input level
If an approximation of the INL(n) curve using polynomials is applied, the third order polynomial is mostly sufficient for the following integral non-linearity correction
Summary
The ADC non-linearity is inherently described by the Integral Non-linearity curve INL(n) which is defined as the difference of ADC output and input as the function of the input level. If an approximation of the INL(n) curve using polynomials is applied, the third order polynomial is mostly sufficient for the following integral non-linearity correction. H =1 where ah are the nonlinearity coefficients up to the maximum order Hmax, which is the highest harmonic component considered, n is the normalized ADC code with a bipolar range, and x the ADC input. Having the coefficients ah and the approximation of INL(n) curve, the non-linearity of digitizer can be corrected. If the transfer function TF is monotonical, its inverse exists For this case, let’s propose that the approximation of the inverted transfer function TF-1 will be a polynomial of the same order (Kmax = Hmax) defined as. In the first method the coefficients b1, b2, b3 are determined from 3 loworder equations, the equations with polynomials nl, l > 3 are neglected. The coefficients b1, b2, b3 can be calculated by applying the Cramer’s rule based on determinants det(C1) det(C)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
