About Franz Seifert
Franz Seifert was born in Vienna, Austria on May 4, 1933. He joined the Vienna University of Technology in 1961 as a student and has been there ever since as a Research Engineer (1961-1967) at the Institute for Microwave Engineering, as a Senior Research Engineer (1967-1974) at the Institute for Physical Electronics Engineering, and following his habilitation in Electronics, as a Professor for Applied Electronics (since 1974). He received the Dr. techn. degree in 1965 under the supervision of Herbert König. Franz Seifert mentored numerous doctoral and habilitation students to become leaders in industry and academia in the field of electronics engineering, especially in the areas of (i) spread spectrum techniques, (ii) surface acoustic wave devices and their applications, and (iii) numerical modeling of fields and waves. Franz Seifert passed away in his house in Vienna on February 7, 2016.
In this interview Seifert describes his childhood in Vienna and in Mittersill, his education in Vienna, his family, his research work, and his cooperation with partners, especially with Siemens in the surface acoustic wave arena.
About the Interview
FRANZ SEIFERT: An Interview conducted by Clemens Ruppel and Robert Weigel, Vienna, August 24, 2015. Interview #753 for the IEEE History Center, the Institute of Electrical and Electronic Engineers, Inc.
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It is recommended that this oral history be cited as follows:
Franz Seifert, an oral history conducted by Robert Weigel and Clemens Ruppel, Vienna, Austria, August 24, 2015
INTERVIEWEE: Franz Seifert
INTERVIEWERS: Clemens Ruppel, Robert Weigel
DATE: August 24, 2015
PLACE: Vienna, Austria
The Early Days
Franz, you were born in Austria in 1933 right after Mr. Hitler had overtaken power in Germany. What about your early days?
Born on May 4th 1933, I had a happy childhood in the garden of my grandma’s inn, in woods and on skiing slopes at Vienna’s outskirts. I was pampered by sister, mother, and grandma and my father. Our house had been built in 1879 by my grandma’s grandpa. Its electrical installation needed repair often, which was done by my grandpa. I watched him at renewing fuses with thin copper wire and he taught me the taste of electric charge of a battery with the tongue at its copper brass contacts.
This exclusively happy time ended on September 15, 1939 when I was drawn into school and simultaneously WW II began. In school we had a kind of old teacher who showed us two different writings of alphabet and the art of multiplication by knocking on our heads with thin bamboo for each wrong result or poor attention or fallen asleep even. But beginning at the age of 8 for two days of the week we had to attend political indoctrination, taught by older boys with German national songs and tough sports. This, I didn’t like at all. When the US army had occupied Sicily, bombing of war-relevant factories and traffic centers in Austria started in autumn 1943. The school pupils were evacuated from the cities. My school class was sent to Mittersill in the Austrian alps on March 4th 1944. Here we were exactly on the trails of the US bombers to Munich. Usually the air raids started at 9 am with the exhaust gas trails of some hundred heavy bombers. Until noon the sky was clouded totally and bombing could be heard faintly. Most of the planes returned undamaged but some were burning.
On February 21, 1994 my sister was born in the hospital of Mittersill , I went to visit my mother a few days later. There, I watched 2 light wing double bridge fighter planes to collide in a huge ball of smoke. One pilot came down in parachute on a meadow, where only one broken tree was standing. The pilot fell exactly at the top of the tree. I ran to the farmer owning a telephone and met the farmer who laid the pilot on a ladder wagon stuffed with hay and brought him to the hospital. There, I saw a black man for the first time in my life. Next morning our English teacher told us that she was called to the dying pilot and he had asked her to write goodbye to his mother and sisters.
At the same time Vienna suffered from bombing, too. After each day of an air raid I was very anxious about my family since they did not send me a “sign of life card”, whereas the other boys got this small red post card one day after bombing of their home district.
How was your education?
War ended for me on my twelfth birthday, when the US Rainbow Division took over Mittersill without any fighting. Some tanks stopped on the marketplace in ring-shape. Although it was risky, we boys came out to the tanks and the young GIs climbed off the tanks. There, I got a chewing gum for the first time in my life. We were happy that the thread of war was gone but life was not easy at all. Food was sparse.
On the way from the Kinderlandverschickung (The sending of children to safe places in the country side to protect them from being bombed was called Kinderlandverschickung) to the house where my family lived, I met a GI named Snuffy. His name was painted white on his helmet and he had a paper bag in his hands and looked around. I asked him: “Snuffy what are you looking for?” He showed me what was in his bag: brown green underwear needing to get washed. In our house we had one small cooking stove with a big pot where the diapers of my sister were cooked together with all our and Snuffy’s clothes. When he fetched his underwear he brought us army food bags.
I had a year of valuable education in the school of Mittersill. Fundamentals of mathematics became familiar and my fascination of radios was enhanced by a good radio amateur booklet I found. A plenty of earphones, coils, tuning capacitors etc. was left behind by the German troops and the key part of my detector radio, a pyrite crystal I traded for a fishing loop from a friend in my class, whose father was working in a copper mine. My first detector radio worked well with a long wire antenna.
Next year our family returned to our house in Vienna, which had suffered only minor roof and window damages, though many neighbor’s houses were totally destroyed. Since in our garden we had chicken, rabbits, goats and even a pig we had enough to eat and my grandma operated her inn. My help was the supply of hay for the goats. In exchange I got a small room where I could improve my radio receiver with steel case radio tubes, which I had found on the waste deposit of the US army near our house. Vienna was sectorized into 4 occupation zones and we were lucky to be in the American zone. My most advanced radio was a super heterodyne with 4 steel tubes. I built some models for my friends and tried to sell one with no success at all. My performance was better in repairing of old radios and other electrical appliances and playing basketball in the Vienna league since at this time I was nearly 2 m tall.
Diploma and PhD
What was the topic of your PhD thesis?
After successfully passing secondary school I matriculated in the Technische Hochschule (which was later named University of Technology (TU Vienna)), heard boring lectures in mathematics, physics, engineering, etc. and earned a little money with short jobs in building of houses, in telephone companies, and working for a music box loaner who imported used Seeburg and Wurlitzer juke boxes from New York. Here, I had heavily troubles to repair a stochastic disc selection malfunction: after total disassembly of the box I found at the bottom in a heap of glass debris a lead bullet of a revolver making the wrong disc selection. This was one way of earning money another was to give lessons in a repetition school. But more joy I got from working for two friends - Rudi Stampfl and Kurt Richter - who had asked me for. Rudi lived in a neighbor house and yet his grandpa was a friend of mine. Being 6 years older than me Rudi served in WW II and studied communication engineering at TU after his release from army. Now he was completing his PhD thesis: “ 4 Channel Pulse Position Modulation” and I helped him with the audio frequency and the digital part. After graduation Rudi worked for RCA and NASA in Princeton and died as a high NASA officer some years ago.
Kurt Richter I met in exhausting basketball matches and at matriculation of our common course of study at TU. We became friends chatting and playing cards between lectures at TU. Kurt was a bright and very effective student. Faster than I after passing his diploma, Prof. König offered him participation in his group of hopeful PhD students (most of them were very successful later) with a thesis on the investigation of the impedance of diodes up to 1 GHz. The diodes were fabricated at Siemens by removing the grid of microwave triodes, which Prof. König could achieve by friendly persuasion of former colleagues. In WW II König, working at Siemens had constructed the 1,3 GHz German radar klystron and analyzed the English 10 GHz radar captured by the German army near Dunkerque. So it was a great honor for Kurt to work at König’s institute. Kurt already had theoretical results for diode impedance, when he asked for help in its measurement. Kurt and his coworker Bimi Tögel tried to measure diode impedance with a slotted line. This didn’t work, since the diode impedance, I estimated at several kiloohms, was totally unmatched to the line impedance of 60 ohms. So I had to change the principle of measurement from slotted line to resonator measurement with the diode as the resonator’s capacitance. By applying a variable negative voltage to the diode, its impedance could be changed. Consistent with Kurt’s and Bimi’s calculation I even could observe a voltage range of negative resistance where the diode worked as a tunable generator. Prof. König didn’t believe this, because he knew publications where a filament power of 300 W was necessary to make a diode work as a generator. So he personally came into the laboratory room, had a look at my 1,8 W (6 V x 0,3 A) diode generator at 600 MHz and finally gave me his congratulation. The calculations of Kurt and Bimi had such a nice fit to my measurements that both got their PhD soon and left König’s institute. Bimi became director of a Viennese College of Technology and Kurt, after some years of work in the US came back to Austria as a full professor to the University of Graz. He is still giving interesting lectures for IEEE all over the world.
In spring 1961, I graduated as Dipl. Ing. and got a job offer connected with a PhD chance by Prof. König.
Now let’s come to your research, Franz.
Research, okay. Although music box repair would have paid better about 30 % more, I took this chance and started to measure semiconductor resistivity at microwave frequencies. Payment for this work came from Columbia Broadcasting System (CBS) in 3 months shares. We had to measure the resistivity of Germanium and Silicon slices fitted into an X-Band waveguide. This was relatively easy for high resistivity samples by slotted line method, but it was not possible for low resistive samples. For this I invented a wall replacement method: A resonator made of unusual X-Band waveguide was cut out along lines of current flow. So rectangular and nearly circular windows originated and for measurement were replaced by low resistive semiconductor plates. By quality measurements of the cavity the surface resistivity of the samples was determined. Due to the current flow cuts radiation losses were avoided, which were problematic in slotted line measurements. For this special cavity measurement I applied for a patent, having heard from a dramatic letter Prof. König got one morning from Siemens: they asked for his help, since the company Varian, the producer of reflex klystrons requested millions as patent fees for the claim of electron transit angle. Prof. König called us, his group of hopeful PhD students, to discuss this issue. Hans Pölzl, who at this time studied König’s work carefully told him that he himself had formulated mathematically throughout his habilitation at the TU Vienna in 1943 the transit angle property before Varian’s reflex klystron patent claim. Siemens could defend Varian’s claim and thankfully helped us all the years in our research work in Vienna very effectively. Prof. Heywang was the director of that Siemens lab.
Another very simple and short cooperation with my friend Gerhard Schiffner at König’s institute yielded one joint publication ranking highest on the citation index. Gerhard’s PhD task was the construction of a gas laser. He asked me to help him to adjust the two concave end mirrors for laser operation. This was difficult and took long. At this time I worked with reflex klystron for microwave generation and observed a jump in anode current when the tube began to oscillate. I proposed to Gerhard to apply my klystron current experience to CO2 laser current. It worked and since than several quantum mechanical explanations of laser current dependence on laser action were published with reference to our experiment. Gerhard’s PhD thesis was the first of some gas laser based developments at König’s institute, which yielded heavy machines for laser cutting and welding. Schiffner worked than as scientist in laboratories at Siemens and became full professor and dean at Bochum University. Before his death some years ago he proudly sent me a New Year’s cards showing at least 20 coworkers around him.
Additionally to my PhD semiconductor microwave measurements, I had to take care of two laboratory tasks for students in the last semester of their communication engineering diploma studies. Both were interesting: super heterodyne and television receiver. Since I had made experience with weak students at a repetition school before, I estimated the quality of the diploma student very high and gave them good marks for their laboratory tasks. Due to my reputation many bright students came to me to complete their diploma thesis under my helpful supervision. With some of them I became friend.
Franz, you have a family!
The year 1962 was the most important in my life. My sister, who already was married, invited the girls of her office to a party in spring. Since there were many girls she persuaded me to come. So I made a ride over the mountain with my motorcycle and met Susanne at the party and fell in love with her instantaneously. I think she also had a good impression about me, since the day before I had returned from a sunny skiing week in Kitzbühel. The following weeks were filled with joint motorcycle riding and being together. The vacation in July she spent with her parents at the Cote d’Azur and I had an accident in the Swiss mountains with my motorcycle in bad weather at Grimsel pass. When coming home Susanne and me found our vacation letters and had good and long dialogues. I learnt that she liked to walk in the woods and on mountains and was singing in a jazz band. This reminded me to my dear grandma, who had been a singer too. I still like jazz more than folk songs.
In October we married. Since than in the past 53 years we got 3 sons, their wives, and 6 grand children. In the past 53 years Susanne has learnt to cope with my slackness so for us the 1962 marriage still works well.
Continuation of Research Work
Hans Pötzl was very important you’re your career, wasn’t he?
Definitely he was! Further developments around 1962 became important for me: Hans Pötzl, who was the scientific leader of the group of hopeful PhD students working for Prof. König excellently defended his habilitation thesis on streaming of electrons. Based on this work Hans Pötzl got the invitation to become professor in Electronics in Karlsruhe, but Prof. König convinced the Austrian Ministry for Science and Education that at TU an institute for transistor technology was absolutely necessary. So, applying the Austrian rule of Berufungsabwehr (defense of foreign call) the Institute for Physical Electronics was created for Hans Pötzl as full professor and some positions of assistant professors, technicians, etc. later. In the meantime Hans got a positive impression of my work, being examiner of my diode measurement diploma thesis and the first microwave resonator measurements of low resistive semiconductor slices. So he asked me to become his assistant which was not necessary at all, since I had a grand opinion about his human and scientific qualities and would have taken this job for half payment. Soon we became friends and remained friends for 30 years until his deplorable death by cancer in 1993.
When Hans Pötzl was appointed professor for Physical Electronics in 1966 he was the youngest full professor of TU at this time and he fulfilled his job very seriously. The preparation of a lecture on semiconductor physics and transistor applications was very time consuming. Nearly each day in the week up to Friday he left the institute not before 9 o’clock in the evening and on Saturday at noon. The effect of his demanding lectures on students was twofold. One group was enthusiastic in learning the applications of new solid state devices and the other group had to study intensively for examination. But no student ever was treated unfair or impatiently by Hans.
For the position of assistant professors at Physics Electronics remarkable PhD candidates were selected: Peter Russer, Erwin Hochmaier, Ditram Kranzer, Erich Gornik, etc. We all became friends soon. Like me they are standing at the end of their professional career. Erich Gornik is professor in microelectronics in Vienna and gives lectures still. Erwin Hochmaier met his wife Inge, a clever and beautiful girl in our lessons, then developing together with her the first wireless cochlea prosthesis. For this she has built a worldwide operating company for doctors who implant it behind the ear. Now they have several hundred employees around the world. Erwin is professor of physics in Innsbruck and Inge gained the title Austria’s Business Woman of the Year 2003. Ditmar Kranzer worked very successfully in semiconductor research and fabrication at Siemens in Munich, and Peter Russer became university professor and director of a renowned radio frequency institutes in Munich and Berlin.
For me the creation of the Physical Electronics Institute was a lucky event. For the first time in my life I had an employment lasting longer than 6 months.
The director of the institute, Hans Pötzl was my friend and had a lot of ideas for future research due to his comprehensive knowledge of physics and microwave tube calculations. At this time transistors became very interesting, the special research issue of Hans was electric field induced “hot” electrons in semiconductors. Our first PhD student made long calculations of charge transport in semiconductors and I tried to supply measurements of this effect with my microwave cavity wall replacement method, dreaming of habilitation after PhD.
John Whinnery, the author of many good microwave books invited Hans to the University of Berkley. Hans, his wife Edith and their little son Georg spent this time among Berkley students and long haired “beatles” coming from nearby San Francisco. After his return to Vienna Hans told me about his meeting with Dick White, who together with his student Voltmer had published the idea of surface acoustic wave (SAW) applications for signal processing two years before. But we didn’t have the technological possibility to fabricate such fine interdigital structures yet.
But my microwave cavity wall replacement method in the bands X (10 GHz) and Q (35 GHz) became known. So I got the invitation to come to the University of Sheffield by Peter Robson, the main professor there. This February 1969 was very cold. Thick powder snow gave students the possibility to slide down the hill on menu trays they had borrowed from the restaurant. Talking about my measurements I found friendly interested colleagues and Peter gave me the chance to visit Royal Radar Establishment in Great Malvern. At RRE I met Ted Paige and E. Marshall who showed me their first SAW directional coupler and chirp filter. On my travel back over the Channel I became seasick but returned to Vienna full of good ideas. My microwave resistivity should yield active regions, if strong electric and magnetic DC fields were applied to the sample. To this end I built a 500 V pulse generator and a 500 kg DC magnet was elevated to the 4th floor by a crane. The power supply for the magnet was built by a diploma student. In order to investigate a semiconductor with really high mobility an n-type Indium-antimonide sample bar (about 23 x 6,5 x 1,4 mm3) was measured, which was cooled down to 77 K with liquid nitrogen. This InSb bar covered a whole circular cut out of the top wall of a 35 GHz TE210 cavity. Here at the bottom face of the sample a linearly polarized microwave at 35 GHz was excited which on its way through the sample became circularly polarized at its top face due to the perpendicularly static magnetic field B0. Both circular polarizations of these “helicon” waves could be separately analyzed means a normal TE10 waveguide with a small hole in its broad wall at the point of circular polarization of TE10 mode (diesen Satz verstehe ich überhaupt nicht!). Counter rotating circular helicon waves produce counter propagating TE10 modes. These were observed and showed interesting effects of electric and magnetic field dependence for both helicon waves propagating through InSb at 77 K. Erwin Leitner, my diploma student, who became my friend later, helped me with the interpretation of my charge carrier model by the application of a 56 year old calculation method.
All this is published in British J. Phys. C. Solid St. Phys. 1971, pp 1519-1533 and contains results, which were really difficult to get through against the questions of the reviewers.
The amplitude and phase of the helicon waves and their distribution over the samples shows that
- Carriers of charge (high mobility electrons) are excited by the electric field at the cathode.
- They travel to the anode in bunches shape.
- On their travel these bunches are acousto-electrically amplified and fade away at the anode.
- This causes acousto-electrically excited oscillations of helicon transmission and of the pulse current through the sample.
Invention of Acoustic Charge Transport Devices
Hearing about this, let me ask how were your interactions with Bill Hunsinger?
From the observation of the acousto-electrically excited charge transport in InSb I got the idea of signal processing devices based on acoustic charge transport (ACT) in piezo-electrical semiconductors. For these ACT devices I filed a patent at the Austrian patent office in Vienna on the last day of 1971. It was clear for me that ACT needs strong SAW excitation on the surface of the semiconductor together with diodes to collect the travelling carriers. The next ten years some poor PhD students had to suffer from my idea to realize ACT devices at first with 2 simple interdigital transducers on GaAs plates.
The ACT idea spread under colleagues. At first in the Siemens research laboratory in Munich, with its director Walter Heywang I could demonstrate the signal processing capabilities of ACT so promising, that they filed my Austrian patent in all relevant countries. For the US patent 3,792,321 my drawing remained as they were in my Austrian patent, but the text required half the time of my summer vacancies and a lot of work for Mr. Bartels, the Siemens patent attorney in Munich, and that in Chicago equally. In talks at semiconductor conferences, meetings and discussions with colleagues especially from Purdue University I tried to find co-investigators of ACT. In 1983 M.J. Hoskins submitted his PhD thesis “Acoustic Charge Transport in Gallium Arsenide (GaAs)” to the University in Illinois. Together with his professor Bill Hunsinger he published the theory of acoustic charge transport in GaAs in the J. Appl. Phys. and in the IEEE Ultrasonics Proc. 1986. Since at this time Ronald Reagan’s Space Defence Initiative (SDI), the golden age of university support by DoD was at its summit, Bill Hunsinger got a lot of money to develop the ACT devices for SDI. I met him at the 1986 IEEE Ultrasoncis Symposium and said slightly exaggerated that seven PhD students are working on GaAs ACT. He said something I couldn’t hear clearly so I asked him: “Seventeen of your people work on ACT?”
“No” he said, “seventy”. This impressed me intensively. Even more I became upset when in 1990 announcements appeared in newspapers of Electronic Decision Incorporated (Bill Hunsinger’s company EDI) offering ready for use ACT signal processing devices. My partners at Siemens sent me to their patent attorney in Chicago. On May 11, 1990, I came to the 70th floor of the Sears Tower, a beautiful attractive black lady welcomed me and then I discussed with patent attorney Brett A. Valiquet the patent infringement letter to EDI. Then Bret invited me to a good dinner. He sent the infringement letter to EDI and their attorney and had a lot of telephone calls. From my attorney I got 2 invoices with US $ 1823,43 together, but no answer from EDI. At the 1990 IEEE Ultrasonics Symposium in Honolulu I met Bill Hunsinger and we spoke about ACT. He acknowledged the priority of my 1971 patent and promised to send to Vienna 2 ACT microprocessor modules. This promise he repeated in his letter of January 9, 1991 when he explained the necessity of an export license from the U.S. Department of State, to get within 90 days. This was the last information from Bill Hunsinger since then. EDI went down completely. Compared to present day digital signal processing circuits ACT devices were too complicated and expensive due to manual fabrication.
More Research Work
What about Fritz Paschke?
Fritz Paschke began his career as König’s PhD student, had successful employments in the US electronics industries, then became professor of electrical engineering and elected rector of TU Vienna 1972 to 1975. Together with Hans Pötzl and me he initiated the construction of a technology laboratory for electronic device research. He gained Dr. Wolfgang Fallmann from the University of Newcastle, where he had worked in the semiconductor lab. Wolfgang was one building architect of our technology lab and Fehti Olcaytug the other. The lab was used to assemble many research devices, e.g., ear prostheses of Erwin and Inge Hochmaier and SAW filters for many PhD students.
Franz, you had so many PhD students, do you remember?
In Vienna my ACT idea requested at first a transducer to generate strong acoustic impulses. Our first PhD student Hans Reichard built a single-phase impulse transducer by synchronous coupling of an electrical delay line to a multi-finger structure at a plane GaAs surface. At the same time Gerald Tobolka elaborated and published his P-matrix model for the design of common interdigital SAW transducers, which was cited very often. Each year in March he arranged for the professors, assistants and PhD students a scientific workshop in Kleinarl. It started in the morning with lectures, as snow was very icy until about 11 o’clock. Then skiing began and lasted as long as ski lifts were operative. In the evening we had lectures and discussions.
The superior quality of SAW chirp pulse compression in a blood flow-meter based on Doppler analysis was demonstrated by Gerd Riha. He fabricated two SAW chirp filters on Bismuth Germanium crystals. Thanks to the low SAW velocity on this substrate a time-bandwidth product TB=80 could be achieved. Doppler analysis of the compressed impulse yielded the blood flow in the vain. At this time (around 1970) this analysis was new, now it is standard. After finishing his PhD Gerd went into the rising SAW lab of Siemens in Munich and after some time became a leading scientist there.
The original design method for SAW filters was based on Fourier transform of the required transfer function, measurement and empirical corrections of the finger structure. In this way the first TV intermediate frequency (IF = 36 MHz) filters were produced and replacing coil and capacitor filter became profitable soon. The number of different SAW applications increased and for these the perfect numerical design should replace cut and try methods. For this PhD job Siemens paid for the first time the employment for Wolfgang Mader. Wolfgang took into account wave diffraction and electrical charge distribution on the transducer fingers. By compensation of these secondary effects his filter design brought an improvement of 20 dB compared with former methods. Wolfgang achieved a promotio sub auspiciis praesidentis as the first of 4 of my 40 PhD students in my university career. The promotio “sub auspiciis” award of honor originally in the Austro-Hungarian monarchy was “sub auspiciis imperatoris” and now and then given to promoting PhD candidates if in all exams the best achievable result were reached. As a gift the promoting PhD gets an engraved gold ring and a dinner with the imperator (now president of the republic). The assisting professor has to give a laudation in the university festival hall. In our physical and applied electronics group Hans Pötzl had the first sub auspiciis candidate. My candidate Wolfgang Mader had his promotio sub auspiciis about 2 years later.
Before 1980 chirp filters were developed by Gerd Riha on Bismuth Germanium substrate and on quartz by Helmut Stocker for IFF88. Both went to Siemens Munich. For Wolfgang Mader’s computational thesis and many similar ones one fact was important for which I have to thank Austria. Great computation facilities and all software were provided by our university for scientific use without of charge, in this IFF88 and SAW filter calculations were included.
In discussions of our military work with chirp SAW filters came out that security of deception is lost whenever an enemy gets knowledge of the filter structure. But for the military defense of trustee in cold war, a three weeks period of security was considered by officers to be enough. But in Munich, NATO defense considered that this has to be much better. So, a device, which was a programmable SAW correlation filter with some MHz bandwidth, a convolver, was developed by Hans Graßl, while we in Vienna implemented our simple chirp IFF in Goldhaube. After successful tests of the convolver and good exams Hans was promoted in the biggest lecture theater of TU. To this he and his family (wife and 2 daughters) came from Munich and stayed in our house. When they came to dinner after promotion, my wife Susanne asked the 4 year old daughter:” How was the doctor celebration?” She answered in Bavarian slang: “We were thrown out!” This was true, since her little sister wept loudly during promotion. Two weeks ago now Hans has sent me an invitation to his retirement speech. As director the of the Landshut Electro-technical College he retired last week. The perfection of the convolver design was a several years PhD thesis of Leonhard Reindl. When he jumped into the footsteps of Hans Graßl, first comprehensive design procedures for chirp filters were known in 1985. When he was promoted in 1997 many important steps to a perfect SAW design had been made by him. Many inventive ideas are realized in his impressive convolver, which at this time was superior to all digital signal processing. The main field of cooperation between the world leading SAW development and fabrication laboratory at Siemens Munich and my group of diploma and PhD students in Vienna was SAW filter design. The description here is a compilation of my chronological records.
In 1986 Clemens Ruppel, who had studied Mathematics at the Ludwig Maximilians University in Munich, submitted his PhD thesis “Design of SAW Filters” to TU Vienna. Its assessment had to come from both universities: Munich and Vienna. Prof. Sachs from the mathematical institutes of the Munich university writes in his votum informativum that Clemens, based on his many years experience had solve that very complicated problem in several steps of optimization, splitting it into a linear and non-linear phase, applying coordinate transform, sampling theorem and factorization. Knowing the outstanding design result of Clemens and having very poor mathematical education myself all I could do was to give Clemens the best possible judgement.
Oswald Männer gave a new method of SAW filter design, which also takes the ohmic resistance of the metal fingers into account in his fine PhD thesis.
Because of a relatively long cooperation and his headstrong behavior I became a good friend with Alireza Baghai Wadji. After his diploma he joined my group with employment in our SAW research project and teaching. With the university recommendation the application for Austrian citizenship was treated positively for him and his family. But nearly without delay Alireza had to become a soldier for half a year in the Austrian army and to water the lieutenant’s garden in the morning. At noon he came to the institute and proceeded with his PhD and habilitation thesis respectively. In this work he treated the excitation of SAWs by the electric charge distribution on transducers and other metallizations on the substrate surfaces comprehensively employing Green’s function. He became Dozent in Vienna and had Mohammed Manzuri and Morteza Chehrehrazi after their diploma in Vienna as PhD students. Both were promoted in 1996 and Ali went to Motorola in Scottsdale, Arizona. Later he became professor in Australia and then improved his position to professor in South Africa.
Giuliano Visintini who came from Southern Tyrol to Munich takes the Green’s function approach, which was introduced by Alireza and attained an outstanding agreement between the computational and measurement plots. He owns now an electronic company in Munich.
Karl Wagner coped with the prior disturbing problem of bulk waves in SAW filters. He began with known solutions for Green’s function at substrate surface and extended this into a 3D wave field within the substrate. This is verified by measurement. This method can be used as well for SAW as for bulk wave devices. Karl has submitted the best PhD thesis of my 40 years university teacher career and achieved the best achievable marks throughout his college and university study. He is one of my 4 out of 40 students promoted sub auspiciis praesidentis. Now he works as chief scientist in the Munich SAW laboratory, which after Siemens was called EPCOS and now TDK.
Christian Kappacher opened the new aspect of time-frequency (Wigner) distribution for the addressable correction of errors in the interdigital structure.
Gilles Sindic treated the development of a dispersive SAW filter on lithium niobate for a compressive receiver with very large TB >> 1000. He used finger width rather than overlap weighting.
Wolfgang Wallnöfer presented an investigation of Galliumorthophosphate for all kinds of acoustical wave applications. He worked at Prof. Benes institute of Physics at TU Vienna.
Helmut Bachl’s thesis on efficient modeling of the electric source distribution in SAW devices delivered an appreciable increase of accuracy of design.
An outstanding thesis was submitted by Bernhard Jacoby: “Analysis of Electro-Magnetic Fields in Stratified Complex Media”. It was a great scientific description and solution of this problem, where SAW applications are only special cases. For me, the review of the second reviewer, Gottfried Magerl brought a negative critic as responsible professor for this work as a single case among about 50 PhD reviews I gave: Gottfried writes, that I should have asked for more nearness to practical electrical engineering than for a chosen demanding complexity. Maybe this is due to my character, preferring a sloppy smile to a serious frown in talks with PhD students. Gottfried retired last year as very important professor of our TU Vienna and Bernhard Jacoby is a very important professor of the university of Linz.
Herbert Zidek, in his thesis “Modeling and Analysis of SAW Finite Aperture Transducers”” takes in his model the real transducer geometry, thus making approximations unnecessary. Two examples demonstrate the efficiency of his method.
Heinz Reichinger wrote the thesis “ Mass Loading Effects in SAW Devices”. With increasing frequency the ratio of finger height to width ratio increases, i.e., bulk acoustic waves gain more importance compared to SAW. With his physical concept of BAW, Heinz achieved improvements of SAW simulation and design.
The TDMA (time division multiple access) thesis of Zhongping Zhang was a transition of a device oriented to a system oriented research period in my life. This began with the work of Alois “Ossi” Goiser who originally worked in my lecture “Introduction to electrical engineering for computer technology students” with up to 400 students attending. Ossi loved mathematics and submitted a thesis “A Stochastic Method to Suppress Interference in Digital Direct Sequence Spread Spectrum Systems”. It was an impressive application of probability calculus to disturbed transmission systems and it was a fundament to the TDMA system I suggested to Zhongping.
With Hans Graßl’s convolver available and a radar measurement project in the huge foundry halls of VOEST in Linz we tried to get wireless transmission in this hall full with a lot of interference. In his thesis “A Convolver Based Spread Spectrum System” Werner Pietsch presented a good solution of this problem. In a signal to noise ratio of -6 dB he got a bit error rate of 10-4. It should be mentioned what he measured in this factory hall in Linz. My old friend Julius Grabner, whom I knew from my 3rd semester mathematics lectures, to which he came with his yellow Puch TF motorcycle whereas I only had a black bicycle for the 20 km way distance, was employed at VOEST Linz and told me about his problem. Some melting processes of the air blast furnace had an overcooking of the furnace, which was not observable. A man was burnt by the molten iron. Julius and me thought about radar observation of the level of the molten iron in the furnace. At first a 3 cm (10 GHz) radar was developed by my PhD student Roman Turba. This could not look through the hot iron steam. So we increased the radar frequency to 35 GHz. The molten iron level was observable and blast was switched off if it became to high. No person burnt anymore and Roman got his PhD.
Austria paid appreciable contribution to CERN, the European Center for Nuclear Research in Geneva. The money partially came back in funding to our physics faculty research at the Large Hadron Collider (LHC). For this work Austrian electrical engineering students got certain tasks for development of particle detectors, synchronization integrated circuits and track finder processors in the Compact Muon Solenoid (CMS) and high density digital links. In contrast to my job in SAW design theses, where I took care from the start of the work, for these four theses I got the work ready and reviewed by competent colleagues at CERN. In order to see what had been done, I was invited to CERN. Susanne together with me had a beautiful ride to Geneva. At CERN the elevator carrier me down 100 m below ground to the collider experiment tunnel where I saw the 3 m diameter magnet solenoids and the 8 m diameter particle detector rings. I learnt that CERN experiments were only possible in the night hours when no train ran causing vibrations of the 28 km long circular acceleration tunnel. The EE students were Christoph Posch, Thomas Toifl, Alexander Kluger and Martin Mandel. They all were promoted at EE faculty of TU. Günter Kleindl and Thomas Toifl, both were promoted sub auspiciis praesidentis.
Because I was examiner in “Electrical Measurement Technology” also I had students with theses in this field. Franz Winkler submitted “Contactless Determination of Electric Current in Wires”. Michael Wiesinger “Development of an Exhaust Gas Mass Flow Sensor”, and Rahimi Shakmirzadi “Range Measurements by Means of Electro-Magnetic Waves”.
Two officiers of the signal battalion of the Austrian army investigated in their work an important question for the Austrian army: “Quality Analysis of the VHF Frequency Hop Multipath Channel in Alpine Environement”. These measurements became feasible for the first time because accurate relative timing was possible employing GPS (global positioning system). Two GPS receivers were used, each mounted on a four-wheel truck. Over night the two receivers were synchronized to the at a time visible satellites of the GPS system and synchronization kept measurements of the delay and quality of the FH radio channel with one truck moving over mountains and woods, etc. The two officers were Gerald Berger and Helmut Safer.
An experimental work which began at Siemens Munich and was finished in the Paul Drude Institute in Berlin, Prof. Fröhlich. Was the daring attempt “Realization of a Segmented Acousto-Electric Amplifier on n- and p-Galliumarsenide” by Faris Kalabic. Two interdigital SAW structures for 200 MHz and 1,2 GHz respectively were photolithographically made on n-GaAs and p-GaAs substrates. Acousto-electrical amplification could be shown for the first time on p-GaAs.
Herbert Knapp: “Realization of Optimized, Monolithically Integrated Oscillators and Frequency Divider for Microwaves in Si and SIGe Technology (1999)”.
Hans-Dieter Wohlmuth: ”Monolithic Integration of RF-Oscillstor in Silicon Bipolar Technology (2000)”.
Klaus Anfinger: “Silicon-Germanium Microwave Frequency Bipolar Transistors (2001)”.
Talking with these ambitious and clever colleagues gave me good insight in actual rapid growth of semiconductor frequency limits and device quality.
But more fun and interest I had with a new aspect of SAW technology in my applied electronics laboratory. It was started with the work of Alfred Pohl “Wireless SAW Sensor Devices”. When Alfred began in my group he already had a lot of industrial experience, having worked for Siemens Vienna after his diploma. So he had many ideas for applications and in our group climate of invention and new device from experimental work testing ruled our work until my retirement in 2002. This climate also was enhances by a good financial help from EPCOS, the successor of Siemens Munich for experiments in railways trains, RF transmission systems, car tire test sites.
Alfred Pohl was the first one who became aware of the possibility to make sensor systems with SAW devices only employing the technological fabrication methods that Siemens mastered perfectly. An example of a new sensor system was the brake temperature measurement for the disc brake of railway wagons. The SAW sensor identification (ID) tag with its antenna was mounted on the disc and the request transmitter with antenna for an 856 MHz request impulse on the outer bottom of the wagon. With LiNbO3 transponder tags the system worked up to 1600 C and we tested for train speed up to 140 km/h.
Gerald Ostermayer submitted “Multiple Access in SAW Sensor Systems”. Following Alfred’s ideas Gerald investigated the possibility of readout of 4 simultaneously addressed LiNbO3 SAW sensor chirps with different chirp codes. The system was simulated and tested employing a SAW convolver. Calculations and measurements yielded an accuracy of temperature readout of 1 degree temperature for all 4 chips.
Reinhard Steindl’s thesis “ Impedance Controlled SAW Transponder for Sensor Systems” extended the method of wireless SAW ID readout to commonly used sensor devices. At the Hörbiger company, who make gas pumps for the natural gas industry, the wearing of a piston ring with a diameter of 50 cm was measured employing a capacity sensor connected to a SAW ID transponder. Similar measurements were made for Continental tire pressure and rubber wearing at speed up to 200 km/h.
Martin Brandl made his PhD with “Data Transmission System with Chirp Modulation” in the industrial scientific and measurement frequency band (ISM) working in a multipath disturbed environment normal data pulse wireless transmission with allowed 10 mW power and suffered from a low bit error rate (BER). He used Siemens produced linear chirp filters with B=80 MHz, T=0,5 s to built an SSS for the ISM band at 2,4 GHz with 3 variations.
- normal binary on off keying with up and down chirps
- position modulated (CPPM) single chirp system
- frequency coded CPPM system with taperd SAW chirp filters
He theoretically and experimentally showed that BER can be improved using sophisticated coding schemes. Selectively it can be improved with method 3). All this SSS work was accompanied by the habilitation of Ossi Goiser, who is now professor at the institute were I began in 1959 at Prof. König. Ossi wrote a renown thick book of the mathematics in SSS.
From his productive and inventive life at TU, Alfred Pohl came into the school and political business. At first he founded an electrical engineering college in Mistelbach, his home community with 350 students at present and Alfred is the director. Alfred also won the election as major of Mistelbach twice with absolute majority. An increasing part of this 350 students came from the neighbor country Czech Republic and all have to learn electro technical English.
The SAW Based IFF System
Franz, you had a very good collaboration with the Austrian Army. Can you tell us about it?
Additionally to the Siemens funding my group got help by an enjoyable military SAW chirp project. One day, a former diploma student, Otto Franz, came to me to chat about secure wireless communication. He had got an employment at the Austrian ministry of defense. I explained to him the advantage of SAW chirp systems and invited the interested gentlemen to visit our laboratory. They came, one morning and our seminar room was full of officers in shining uniforms, with the highest Austrian officer GTI Othmar Tauschitz leading them. Having learnt from many IEEE military electronic articles I tried to explain to them that wireless transmission using TB=1 pulse is not secure in principle independent of cipher encryption, the reception, storing and repetition of signaling pulses allows deception by not authorized person. But if pulses with TB>>1 are used, the eavesdropper needs a matched filter. So our SAW chirp filters are good for wireless communication with pulse expansion at the transmitter and matched filter pulse compression at the authorized receiver. Since we could show such filters, we got paid Helmut Stocker and Max Kowatsch as PhD students for a secure transmission system development. All project employees had to sign a secrecy promise. Otto Franz came and told me a rumor: In the Jom Kipur war 15 % of downings were by friendly fire. So the ministry of defense extended our project: Develop an IFF (identification friend or foe) system for the new fighter planes (Swedish Draken) and the Austrian defense system, called Goldhaube (gold hood). For the demonstrating project I got paid 4 PhDs, 2 technicians, a seem sealer (which did cost the equivalent of 5 years PhD wages), necessary conference visits and all instruments and materials, devices, etc.. A happy time began with visits of my group to IEEE conferences (Ultrasonics Symposia) all over the world in the same field of electronics. I even got the admittance to military laboratories in California and New York, which also were in their golden SDI period.
We worked in the laboratory together with several diploma students and had our “brain storming” session on Friday morning. This meant: everybody should talk freely about his working problems and idea for the future. It is forbidden for everybody, inclusively myself to say: No it will not work. Helmut Stocker and Max Kowatsch were the first PhD candidates. Helmut built his well working SAW chirp filter on a quartz substrate and Max calculated the limits of chirp pulse compression and the analysis of the surface movements means a synthetic aperture radar with extremely high TB. Hans Lafferl investigated and built the circuits of our secure SAW chirp IFF system. Bernd Eichinger and Manfred Sust went into the details of the system. Manfred tried to design a digital solution for a secure IFF, which came out to be too big and heavy (50 kg). Georg Penny together with our technician Klaus Donschachner, Hans, Bernd and Manfred made the changes of the secondary radar of Goldhaube to the chirp compression IFF system. The original 1kW radar request impulse had to be changed since a TB=20 yielded the same communication range of 300 km for Goldhaube as installed originally. My good nerves and electrical engineering experience also were necessary to make this IFF88 system flowless operating. We had built up the system with small (20 x 10 x 5 cm3) immersible transponder boxes to be exchanged with the everyday boxes containing the transponder for civilian or cipher encoded military use in the body of the Draken fighter planes. For Goldhaube radar towers we had built switchable secondary IFF88 radar drivers in microwave coaxial tubing circuitry and tested the system in enjoyable flights within the 300 km range over Austria as far as possible. It operated perfectly and even listening to eastern neighbors radio intelligence gave no indication of disturbance by IFF88 for them. (In 1968 this had given an early picture of the occupation of Czechoslovakia for our military intelligence.) Then IFF88 was transferred to the Schrack company, which was in charge of the Goldhaube system to be built in professionally in all radar towers.
After that, several months later the technician of Schrack came to me at the institute and reported that IFF88 secondary radar worked incorrectly due to feedback from the SAW matched filter. I estimated at this time, that IFF88 had costs of many millions of Austrian shillings but trusting the eternal laws of electricity, I didn’t become nervous when he drove me out to the Goldhaube radar tower. Here, a look into the secondary radar driver circuitry gave me a hint on the error; they had replaced our microwave tubing circuitry by a printed board “professional” driving circuit and that the driving pulses of the chirp filter ran along the edges of the PCB print board. Due to an insertion loss of some 60 dB of the chirp filter the critical feed through originated. This in mind I asked the Schrack technician: “Where does current flow?” He answered bewildered: “Everybody knows where current flows in a PCB, but nobody cares for that”. Then I showed him the edge of feed through and ordered to take our microwave tubing circuitry again. Since than the Schrack people greeted me with the question “Where does current flow?” and IFF88 is okay. Until 28th January 1991 I believed that we had developed IFF88 for the museum only because cold war was over in 1990. But on this day the secession war of Slovenia from Yugoslavia came into action with an air raid against the Slovenian fortifications along the Austrian border. Evidently the Yugoslavian MIG pilots flew this attack with the cold war deception system switched on. The Goldhaube observed the starting of one Draken and suddenly it became 4 Drakens because our Drakens had their commercially available cipher encrypted IFF box immersed. On this Friday, 28.06.1991, the second highest ranked Austrian political people’s party had its session for election of a new party leader in the gorgeous hall of Hofburg castle. As members of this party both, the minister of defense and the governor of Corinthia were present. When the election was over and the gentlemen of the people’s party just left the Hofburg it was announced, that low level flying MIGs are over Graz. One secretary of the people’s party told my wife Susanne, that never before she saw the two gentlemen becoming such pale, since both were opponents of the Draken. Then IFF88 was immersed, 400 soldiers mobilized along the Slovenian border and one MIG pilot landed in Corinthia because he preferred to land in Austria rather than in Yugoslavia. All losses of this war where Austria was prepared to defend its neutrality was the broken leg of one soldier who fell from an army truck. Regrettably 80 soldiers and civilians were killed in Slovenia on both sides. Recently I bought a funny book about Austria’s participation. The construction of IFF88 and its implementation in Goldhaube had a strong positive influence on the uprising of my friends in Applied Electronics at TU.
How was the transition to retirement?
At last I report about two interesting journeys and two enjoyable festivities. Robert Weigel and I were invited to an international IEEE conference in Jerusalem. We got a friendly welcome there and then visited companies, getting a strong impression of the technological progress Israel had made. Susanne and I were surprised by the strong lifting force of Dead Sea and by the heroic defense of Masada against Roman siege.
The second interesting journey was to New York. Susanne watched the beginning career of the Bulgarian mezzo-soprano Veselina Kasarova in Vienna and liked her singing since she herself had studied singing in her youth and sang jazz and lieder. 1999 before Christmas Veselina had her debut at Metropolitan Opera (MET). On my side, I was interested to talk with the president of the IEEE Communications Society about the SSS work of Zhongping Zhang, Alfred Pohl, Martin Brandl and Gerald Ostermayer and the applicability of SSS and SAW ID tags to industrial systems. So I bought 2 MET tickets and a phone call to the ComSoc president who gave me a date near the MET performance. Having arrived in New York in the nice and inexpensive hotel Seventeen on 17th street I came to the ComSoc president to his house, a one storey single house with a friendly dog. The president also was very friendly and explained to me, that all my positive experimental and simulation results together with my good relation to Siemens in Munich and Vienna don’t help to come into the 802.11b SSS standard with our SAW devices and systems. All that would have helped here would be a majority of votes within the IEEE 802.11 committee, achievable by lobbying only. Since I didn’t understand a bit of that I came to Susanne in Hotel 17. At evening we went to the MET. When the performance “The Barber of Sevillia” began, a well dressed gentleman appeared on the stage and announced that Veselina Kosarova can not sing this evening because of health problems and will be replaced by another mezzo soprano (I don’t remember the name). This lady sang very affected and the mostly Italian speaking spectators correctly laughed at the jokes and became enthusiastic at the final.
Susanne suffered from the strong air condition making her hair flutter and remarked that the acoustic in Vienna’s Staatsoper is better than the MET acoustic. Later we were informed about Veselina’s health problems. It was a boy who is now 16 years old Susanne explained. Veselina became famous but Susanne doesn’t like her lieder singing anymore.
The rest of our New York journey was interesting and comfortable since it didn’t snow, but we both returned to Vienna a bit disappointed.
One totally fine festivity was the 2002 IEEE International Ultrasonics Symposium in Munich. My friends, Robert Weigel and Clemens Ruppel had organized this together with Leo Reindl, Ken-ya Hashimoto, Helmut and Astrid Ermert, Herman van de Vaart, and Reinhard Lerch. All I knew from prior meetings and discussions I was glad since SAW activities had developed so widespread and I was impressed by the magnificent room where the social event took place in Munich castle.
Another enjoyable event was the festivity for my 80th birthday in the splendid rooms of ÖVE, the Austrian union of electrical engineering. Max Kowatsch and Manfred Sust, who are now the leading scientists in RUAG, the successor of Schrack Aerospace who had inherited our IFF88 and now develop space electronics with 200 people, have organized a birthday party with scientific contributions of 10 of my friends. I couldn’t understand all what they spoke about but I had much pleasure to hear of their work in the universities and laboratories in Munich, Freiburg, Nuremberg, USA, Capetown, and Vienna. The Duke Ellington song “Take a Train” was played by a saxophone player hired by Susanne. After the short lectures a good buffet took place in the newly adopted ÖVE sitting rooms and I was happy to observe my family and friends eating at good health.
Susanne reminds me to report my decorations. I have got 2 financial prizes and one silver star from Austria’s catholic church, Chamber of Commerce and Ministry of Education.
Eventually, looking in my record of PhD students I found my gold life member card No. 07903792.
Franz, I’m sure the number is still active, as you are!