There are two mathematical forms commonly used for ADC figures-of-merit (FOM) – the linear form, and the equivalent base-10 logarithmic expression. As an example:
is the logarithmic equivalent of
and both are used in the literature. The mapping between the two is derived as follows: Assume that B is a performance measured in “bits”, and that B is determined by a performance (e.g., SNDR) as
Then
If a generic FOM [1] has the linear form
then we get the equivalent logarithmic form through the transformation
which yields
The scaling with gives the most natural expression for G, starting with an unscaled “dB-performance” term rather than a scaled one in case . For FOMs that does not include a “bits” or similar resolution-related performance, the scaling with is omitted.
A strict mapping between F and G requires , but is usually omitted and M is used to handle various scaling permutations.
References
[1] B. E. Jonsson, “A generic ADC FOM”, Converter Passion blog, On-line, https://converterpassion.wordpress.com/a-generic-adc-fom/, Jan., 2011.
[2] B. E. Jonsson, “Generic ADC FOM classes”, Converter Passion blog, On-line, https://converterpassion.wordpress.com/generic-adc-fom-classes/, Jan., 2011.
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