Background
He was born in Nuremberg, where he studied at the Ohm-Polytechnikum.
He was born in Nuremberg, where he studied at the Ohm-Polytechnikum.
After returning from military service in World War I, he worked at the telegraph research division of the German Post in Berlin as a co-worker of Karl Willy Wagner, and, from 1921, he was lead engineer at the central laboratory of Siemens & Halske AG in the same city. In 1928 he became full professor of general and theoretical electrical engineering at the Technischen Hochschule in Danzig, and later held the same position in Berlin. Küpfmüller was appointed as director of communication technology Research & Development at the Siemens-Wernerwerk for telegraphy.
In 1941–1945 he was director of the central R&Doctorate division at Siemens & Halske in 1937.
Later he was honorary professor at the Technische Hochschule Berlin. He died at Darmstadt.
About 1928, he did the same analysis that Harry Nyquist did, to show that not more than 2B independent pulses per second could be put through a channel of bandwidth B. He did this by quantifying the time-bandwidth product k of various communication signal types, and showing that k could never be less than 1/2. From his 1931 paper (rough translation from Swedish): "The time law allows comparison of the capacity of each transfer method with various known methods.
On the other hand it indicates the limits that the development of technology must stay within.
One interesting question for example is where the lower limit for k lies. So the frequency range must be at least so wide that the settling time becomes less than the duration of a signal, and from this comes k=1/2. So we can never get below this value, no matter how technology develops." K. K.
Küpfmüller joined the National Socialist Motor Corps in 1933.
In the following year he also joined the Société Anonyme. In 1937 Küpfmüller joined the NSDAP and became a member of the Steamship, where he reached the rank of Obersturmbannführer.