Obituary for Alfred Fettweis

Obituary: Alfred Leo Maria Fettweis (1926–2015)

by Abdelhak Zoubir, Technische Universität Darmstadt, Germany

Professor Alfred Leo Maria Fettweis, one of the pioneers of digital signal processing passed away on August 20, 2015 in Bochum, Germany. Our community has lost a giant who made seminal contributions not only to engineering, but also to science. His ideas were visionary and far ahead of his time.

Influenced by the work of Wilhelm Cauer and encouraged by Professor Vitold Belevitch, Dr. Fettweis started his scientific career in the area of classical circuit theory. In his thesis, he wrote in French in 1963, Dr. Fettweis developed a new theory on resonant-transfer circuits that led to a completely new type of application of the resonant-transfer principle, namely, the realization of filters built of capacitances and resonant-transfer switches only; a good overview of this new theory appeared in [1].

Dr. Fettweis later introduced the concept of passivity into the field of digital filtering. With the publication of his seminal article in [2], Fettweis pioneered and paved the way for the most promising field of wave digital filters (WDFs). This attracted the interest of respected scientists from all over the world who started to work successfully in this area; Ruhr-Universität Bochum became the world-centre for research in the area of WDFs. More than 50 postgraduate students and scientists from all over the world (among whom were 13 Alexander von Humboldt Fellows) came to Bochum, some stayed for a few months while others stayed for a couple of years, to get acquainted with the research performed at the Communication Engineering Laboratory, headed by Fettweis. I remember very well the EURASIP Short Course “Wave Digital Filters: Theory and Practice,” held in Bochum, 7-9 March 1989. I was then a PhD student sitting in the course. The lectures given by Dr. Fettweis and other expert colleagues were accompanied by hands-on sessions held every afternoon. With an outstanding quality of both the lectures and hands-on sessions, this EURASIP short course became an unforgettable event.

Beyond the development and improvement of the novel concept of WDFs, Fettweis extended and generalised it to serve as a very powerful tool for the numerical integration of partial differential equations (PDEs). He demonstrated that the strongly nonlinear PDEs encountered in fluid dynamic could be dealt with through WDFs. Numerous papers on the treatment of PDEs by wave digital principles have been published by Fettweis, most of them after he became a Professor Emeritus. Until his death, he continued to work tirelessly on fundamental problems, such as the understanding of the theory of relativity through Kirchhoff theory, and the concepts of passivity and losslessness.

Professor Alfred Fettweis was not only an out-of-the-ordinary researcher, but he also was an outstanding academic teacher. I took undergraduate classes offered by Dr. Fettweis. It is remarkable how much emphasis and value Dr. Fettweis put on the physical relevance and interpretation of the rigorously derived mathematical results; he emphasised that the concepts of Fourier or Laplace transform should not be blindly applied by students, or their properties used as a recipe, but must be understood. One of Fettweis' quotes that I remember until today and mention it when introducing the important concept of causality to undergraduate students is, “causality is such an important physical property that even relativity theory did not violate it …” There was never a mixing between models and reality in his classes, a great attribute missed sometimes in engineering education.

A short bio of Dr. Fettweis:

Professor Alfred Fettweis received his engineering degree (ingénieur civil électricien) and his doctoral degree (doctor en sciences appliquées) from the Université Catholique de Louvain (Leuven), Belgium, in 1951 and 1962, respectively.

After a successful industry career as a development engineer with the International Telephone & Telegraph Corporation (ITT) in Antwerp, Belgium, he moved to academia where he took up the position of Professor of Theoretical Electricity at Eindhoven University of Technology, The Netherlands, and moved to the newly established Ruhr-Universität Bochum in 1967 as Professor and Chair of Communication Engineering. Despite many prestigious offers, Fettweis stayed in Bochum until he became Professor Emeritus in 1992. After a short stay as Distinguished Professor at the University of Notre Dame, USA, from 1994 until 1996, he returned to Bochum, where he was actively involved in research and teaching graduate courses. He also supervised PhD students during that time.

He published extensively in various areas, including circuits and systems, communications, and digital signal processing. His archival work is found in the four languages he mastered, i.e., Dutch, English, French, and German. He also published in the areas of numerical integration, physics, as well as science-related general topics. He held 30 patents.

With his visionary and seminal research, Fettweis earned the highest international reputation, as witnessed in the numerous prizes and awards, which include “the IEEE Centennial Medal” in 1984, the “VDE Ehrenring” in 1984, the “IEEE CAS Technical Achievement Award” in 1988, the “ITG/VDE Karl-Küpfmüller-Preis” in 1988, the “Basic Research Award of the Eduard-Rhein-Stiftung” in 1993, and the “IEEE Millennium Medal” in 2000. He was the first recipient of the “IEEE CAS Society Vitold Belevitch Award” in 2003, and recipient of the “IEEE Gustav Robert Kirchhoff Award” in 2008.

His outstanding scientific achievements have also been recognised through numerous honorary doctorates. He was awarded in 1986, Teknologie Doktor h.c., Linköping, Sweden, in 1988, Docteur Honoris Causa, Faculté Polytechnique de Mons, Belgium, in the same year, Doctor Honoris Causa, Katholieke Universiteit Leuven, Belgium, in 1995, Doctor Honoris Causa, Budapest University of Technology, Hungary, in 2004, Doctor Honoris Causa, Poznan University of Technology, Poland, and in 2011, Doktor der Ingenieurwissenschaften Ehren halber, Universität Paderborn, Germany. He was a member of multiple academies: the German Academy of Science and Engineering – acatech, the Rheinisch Westphälische Akademie der Wissenschaften (Germany), the Academia Europaea (London), and the Academica Scientiarum et Artium Europaea (Salzburg/Vienna). He was a Life Fellow of the IEEE, and a member of EURASIP, ITG of VDE, Sigma Xi, Eta Kappa Nu, SITEL, and GAMM.

His longtime colleague and friend, Dr. Joos Vandewalle, provided an in-depth summary of Professor Fettweis’ professional life:

http://ieee-cas.org/dr-alfred-fettweis

He wrote about Fettweis, “His love for science, art and people, and deep respect for the art of teaching and worldwide involvement in the professional society are reflected in his many international recognitions and social contributions. He leaves us with a lasting legacy."

Sankar Basu, Anton Kummert, and Klaus Meerkötter also wrote an Obituary that appeared in the October 2015 issue of the Springer Journal, Multidimensional Systems and Signal Processing

DOI 10.1007/s11045-015-0360-5

They wrote: “Today, we are living in a digital world of smart phones, tablet PCs, compressed video and audio files that are devices and techniques which appear to be an afterthought for the younger generation. All of these developments are based on advances in digital signal processing going back at least 50 years ago, in which the first steps had indeed been deeply influenced by Alfred Fettweis.”

An oral history of Alfred Fettweis conducted on 24 April 1997 by Frederik Nebeker for the Centre for the History of Electrical Engineering of the IEEE can be found in

http://ethw.org/Oral-History:Alfred_Fettweis

We will remember Prof. Alfred Fettweis as a great scholar and academic teacher, but also as a humble and a congenial person.

Professor Fettweis is survived by his wife, 5 children, and 16 grandchildren.

[1] A. Fettweis, Theory of Resonant-Transfer Circuits, in “Network and Switching Theory, ” Giuseppe Biorci (Ed.), Academic Press in 1968.

[2], A. Fettweis, Digital Filters Related to Classical Filter Networks, AEÜ International Journal of Electronics and Communications, vol. 25, pp. 79-89, 1971 (also available in Digital Signal Processing Committee, IEEE ASSP Society, Selected Papers in Digital Signal Processing, II (IEEE Press Selected Reprint Series, 1976)).

Acknowledgement: I wish to thank Prof. Klaus Meerkötter for his invaluable support.