[sdiy] 90-degree phase displacement network calculations

Bernard Arthur Hutchins, Jr bah13 at cornell.edu
Mon Jan 11 00:16:45 CET 2021




David-you said:

“The reason for the steps is that you must transform the k and k' values using a simple formula until you obtain k = 0 and k' = 1."


The calculation of elliptic integrals is iterative, recursive if you insist, (not closed form) -  even in the most professional signal-processing language, Matlab (see ‘tol’ input variable). You have hidden the iterations by automatically running (non-stop) a large enough (just 8 here it seems) values of j in your for-loop.  It does not matter what you call it.

Your design objective (“output”) should not be the poles, but rather the plot of phase difference (error), of which you only show one final example (the correct 17 extremal frequencies).   If you plotted the error for the different j’s, I think the progression toward a unique-best solution (alternation theorem) might be evident.

I have already said that, as a practical matter, there was nothing wrong with what you did.

-Bernie

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