Confidence Level and Test Time Excel Calculator at Specified BER and Data Rate

     For those who have the experience of receiver jitter tolerance (RXJTOL) test using a bit error rate tester (BERT) build-in function are mostly likely familiar with the configuration parameters such as the measurement BER depth, confidence level, error gating time or transmitted bits. On the one hand, most of the industry standards will specify these test requirements explicitly such as "test at a BER value of 1E-12 with 95% confidence level" and leave you with no choice but to follow. But some will not specify explicitly, thus you need to make a wise engineering judgement for BER, confidence level settings considering the data rate of the DUT to strike a balance between test accuracy and test time. On the other hand, when there is a requirement of DUT and BERT interactions during the RXJTOL test, you have to write your own test codes instead of using the BERT build-in test function. In this case, you again need to have a good understanding of the relationship among BER, CL, data rate and measured error numbers so that your test algorithm can be properly implemented.

    To serve the above-mentioned purpose without sweat on the mathematics, you can actually make use of some online calculators such as the one from JitterTime. You can input target BER, data rate, measured errors and test time to calculate the confidence level. However, if you has a target CL in mind and want to know the test time or number of bits transmitted, then you need to "play with" the test time iteratively until you hit your CL target if use this online calculator. Alternatively, you need to look at the graph on the same website to find your answer indirectly.

    To make life easier, I implemented similar calculators in Excel based on the same Poisson equation. It not only provides the flexibility of using the calculator without the access of the Internet but also provides the capability of calculating the test time and transmitted number of bits for specific CL targets using bisection root finding method with a 0.01 second accuracy. It can be downloaded here and hopefully can be of some use for you.

    Take note, if you find that the Excel calculator doesn't response to your input. It's most likely because of your Excel disabled the Macro.  If that is the case, you need to enable the Macro by going to "Options..." to "Enable the contents" first.