Talk:Küpfmüller's uncertainty principle

Formatting[edit]

Greetings, since this is my first article and I have still some problems with the formatting, I would be grateful, if someone could make some minor changes, like for instance I had problems drawing the equation for a function with restricted preimage, which I tried to write as \u_{\big|_{\Delta f}}, but it looks strange.

I will put in pictures, when I find the time.

Best, Phil. — Preceding unsigned comment added by UnameAlreadyTaken (talk • contribs)

This is a joke, right? Optics researchers call this the time-bandwidth principle, Fourier-limit etc, but it applies to all waves, whether sound (short knocks need many frequencies), light (short pulses need many wavelengths) or electronics (same) and has been known about 200 years before Mr. Kuepfmueller. It is nothing but a fundamental feature of the Fourier transform. [1], [2]. — Preceding unsigned comment added by 174.47.22.18 (talk) 21:57, 9 April 2014 (UTC)[reply]

Küpfmüller was working at a time when the electrotechnology field was just starting to figure out how to apply serious mathematics to their problem space. He came up with a bunch of useful observations and methods by more or less re-inventing what mathematicians could say they already knew. I have not heard his observation on the relation between rise-time and bandwidth referred to as an "uncertainty principle" before, but it surely is related to other things called that, which derive from the Fourier transform characteristics as you note. I don't think the derivation given in the article is his; I will check his book (the 1932 first edition), when I get it un-boxed from my move soon (though this technical stuff can be a challenge to interpret in the math and notation of 1932 in German). He did have the integral of a sinc function in there somewhere as I recall (but not the sinc function itself, as he was more into the indicial response, or step response, than the impulse response). You can see in this paper translated into English that he also cooked up his own version of convolution and a feedback loop stability criterion, about the same time that Nyquist was doing such things, and a good way to analyze AGC loops about the same time as Wheeler; the mathematicians couldn't help you much with that, I bet. Dicklyon (talk) 05:57, 3 March 2016 (UTC)[reply]