SCIENTIFIC PRACTICES: In the previous post, your opinions on which parameters should be mandatory in an A/D-converter implementation paper were surveyed through a poll. In this one we will see what parameters actually get reported in scientific papers, and how the overall reporting practices have changed over time. We can also try to see how well Converter Passion reader’s opinions are in sync with harsh scientific reality 😉
Working with the ADC survey, I had noticed that the set of measured performance parameters authors choose to report or omit changed over time. I’ve gathered the statistics, and it will be interesting to hear what you think of it. Figure 1 shows the percentage of papers reporting signal-to-noise-and-distortion ratio (SNDR), signal-to-noise ratio (SNR), spurious-free dynamic range (SFDR) and total harmonic distortion (THD) each year. The good news is that dynamic single-tone performance is more frequently reported in today’s papers than ever before. In fact, SNDR was reported in 96% of all papers from 2011. Both SNDR and SFDR show noisy but steadily increasing trends, and SFDR is now reported in around 68% of all papers (2011).
At the same time, SNR is increasingly being abandoned in favor of simply reporting SNDR instead. We can also see that THD is becoming an endangered parameter. SNR and THD have been in a visible decline after year 2000, and THD was only reported in 12% of the papers in 2011. SNR went from 60% in year 2000 to 41% 2011. These numbers trouble me. If the trend continues, we will know less about the noise in our A/D-converters for each year. I can’t possibly see how that can be of benefit to “Science” or to the reader. If you can, be sure to post a comment below.
Above we looked at the reporting frequency for each individual parameter. Authors also choose which simultaneous combination or set of performance parameters they include in a paper. This is shown in Fig. 2. Many works report SNDR together with SFDR, and 67% of all papers from 2011 reported at least these two parameters. There is a strong positive trend, so within a decade we may see SNDR+SFDR reported in nearly all published papers. The second most popular parameter pair is SNDR+SNR, with 38% coverage in 2011. Unfortunately, its reporting frequency is limited by the negative trend for SNR.
A more complete single-tone characterization is achieved with the three-parameter combination SNDR+SNR+SFDR. Only 21% of all papers published in 2011 offer this much information about the circuit. Even if there is currently a positive trend, it might soon become limited by the decline in SNR reporting, and eventually reverse.
The practice to report a full four-parameter set is very unusual – only 9% of the papers did that in 2011. It has actually never been really common, and if THD continues to disappear from papers, the four-parameter performance will be increasingly rare. Lots of credit to authors that are still reporting a full set! It is much appreciated here at Converter Passion.
Finally, a few other rare species in the ADC parameter ecosystem are shown in Fig. 3. While the highly valuable parameter self-noise appears to be on its way to extinction, intermodulation distortion (IMD) as represented by the second– and third-order intercept point (IP2, IP3) seems to cling to life in the outskirts of the habitat.
So … what do you make of all this? Do you think it will have any long-term impact on our field of science? Does it matter to you what parameters are reported or not? Have your say in the comments below.
And, what happened around year 2000 to shift the trends so dramatically? Was it the dot-com boom or the Y2K bug? (I haven’t heard about that one for a while now)