Oral-History:Charles Maerfeld

About Charles Maerfeld

Charles Maerfeld.jpg

Charles Maerfeld was born on April 29, 1940 in Paris.

He got his engineering degree from “L’Ecole Supérieure de Physique et Chimie Industrielles” in Paris (1964).

He also got a master degree in Economic Science from Paris University. Later, he transformed an original work on SAW multistrip couplers into a PhD Thesis at Nice University.

He has a long history in SAW activities. His pioneering works started as early as 1969 as he made the first experimental demonstration of the Bleustein Gulyaev wave. He demonstrated the existence of a New Shear Interfacial Wave now called the Maerfeld-Tournois Wave. His detailed analysis of the functioning of the Multistrip Coupler led to the invention of a beam width compressor that he used to build an efficient SAW Convolver.

From this basic research position, he gradually moved into a management one and was in charge of the development of the SAW activity as well as the multi-elements probes for Ultrasonic Imaging systems inside his Company.

This Activity developed primarily components for military applications basically pulse compression radars. But at the end of the 80’s its central part switched to the telecom domain and produced hundreds of millions of SAW filters for the booming mobile phone market. Finally, he was the Chairman and CEO of a Company in charge of SAW and multi-transducer probes for Medical Ultrasound scanners: Thales Microsonics.

He was an active member of IEEE on Sonics and Ultrasonics. He was granted the Fellow grade at the beginning of the 90’s and was elected member of the AdCom in 1989. He organized the first Ultrasonic Symposium ever held outside America in Cannes in 1994, and was the recipient of the Achievement Awards of this section

About the Interview

Charles Maerfeld: An Interview conducted by Clemens Ruppel, Cannes/France, March 24, 2017. Interview #782 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:

Charles Maerfeld, an oral history conducted by Clemens Ruppel, Cannes/France, March 24, 2017

Interview

INTERVIEWEE: Charles Maerfeld

INTERVIEWERS: Clemens Ruppel

DATE: March 24, 2017

PLACE: Cannes/France

The Early Days

Ruppel:

Charles, you were born in Paris/France in 1940 in the days of world war II. What about that time and your early days?

Maerfeld:

I was born on April 1940, the 29th in Paris. This were the very last days of a period known as “the funny war” (in French “la drôle de guerre”) i.e. a surprisingly quiet and peaceful period of the war. But, a few days later, the Nazis penetrated into Belgium and invaded France. My parents, being Jewish, having emigrated to France from Poland to avoid persecution and antisemitism, were so afraid that they decided to flee from Paris towards Bordeaux without any locomotion means. Thousands and thousands of people did the same (not only Jewish) mostly by foot. It was awful. I was only 2 months old. We could see long ribbons of people walking along the roads of France and often got bombed by the Luftwaffe.

After the France defeat, the shamed armistice between France and Germany being signed, my parents came back to their little flat in the suburb of Paris. One evening of July 1942, a French police officer knocked on our door and said: “I received orders to arrest your whole family tomorrow at dawn. If you are still in, I will be forced to execute those orders”. So, the following morning, we were “on the road again”, and French people were so brave and helpful that we were protected everywhere we stayed.

I still remember the glorious days of September 1944 when the American troops pushed the German troops away from the place I was by then, 300 km south of Paris. I was in the crowd cheering a U.S. column of tanks moving northwards. Suddenly, the young lady I was with, lifted me up to the summit of a tank the top of which was open and I finished in a GI’ arms. He kissed me and gave me a marvelous present I had never seen before: a chewing gum!

So then, my family went back to the very small flat in the northern suburb of Paris, from where we had fled in 1942. At that time, my feelings against the German people were so strong that I refused to learn any word of German and even Yiddish seems to me too close to the German language. Therefore, I agreed entirely in 1954 the reject by the French parliament of the Treaty creating a European Community of Defence, referred to CED in France.

But 2 years later, being still a teenager, I changed my mind and I realized that in fact, the European had missed a great opportunity in rejecting this project, and the building up of the European Community appeared then as the best thing that could happen in my young life. And my vision of Germany changed completely. Germany is one important part of Europe which is a tremendous creation of a large community sharing the same values of democracy and tolerance, unique in the world. Despite its failure and rigidity, we should all work in the way of improving its mechanisms rather than trying to destroy it by leaving.

Education, Diploma and PhD

Ruppel:

How was your education, and which degrees did you earn?

Maerfeld:

I have my engineering degree from “L’Ecole Supérieure de Physique et Chimie Industrielles » de la ville de Paris. (1964). The French education system is very different from the Anglo-Saxon’s one. In Science, the most prestigious and rewarding path after Baccalaureat is not to enter a University, but to try to be qualified by one of the “Grandes Ecoles”. To do that, you have to prepare a competitive exam for at least 2 years, to succeed at this competitive exam (at average one out of 10 or 20 candidates are admitted to enter the selected “Grande Ecole”) and then you are educated by this Ecole.

I selected this one because it is the one which has the best results in research and has quite famous directors or professors: Pierre and Marie Curie, Joliot Curie, Langevin, .., and more recently, De Gennes, Charpak and.. Eugène Dieulesaint et Mathias Fink. After being admitted, the education process took 4 years. But no other diploma is needed to be hired in large Companies or at University, even a doctor degree is not considered as higher in qualification.

To be able to finish my studies, I accepted a scholarship from a Company called CSF (which became later Thomson CSF) with the obligation to work in this company for more than 2 years after my study and military service.

Having completed my scientific education, I decided to get an Economy degree, this time from University. I did this study during my military service and my first year at work as engineer at CSF, and then I got a Master degree in Economic Science.

Later, I transformed an original work on SAW multistrip couplers into a Thesis of Doctor from Nice University. But this event had strictly no impact on my career.

Early days at work

Ruppel:

Now let’s come to your early days in work!

Maerfeld:

I started my career in Paris in 1966, trying to develop a new type of accelerometer to be included in inertial platform. After 3 years, being freed from my scholarship contract, I joined in March 1969 a fascinating group led by Pierre Tournois in Cagnes/Mer, near Nice.

This group was a part of the Sonar division of Thomson CSF and was devoted to signal processing at least to improve the sonars performances. Pierre split the group in 2 parts, one using digital techniques, and the second analogue means. I was, with 2 other Engineers (Claude Lardat and Jean Desbois) member of the analogue group. The proximity between the workers in both technics was particularly fruitful. At that time, the performances of digital processors were limited, the first single chip microprocessor was just issued and the analogue processors, we were able to build, appeared to be ultra-fast processors.

At my arrival, the great priority was to develop pulse compression technics. One approach was to use dispersive acoustic waves in different media. Pierre Tournois thought to use Love waves and was developing with Claude Lardat a Love wave dispersive delay line for pulse compression radar. This wave is a Surface Acoustic Wave and the interest converged towards this type.

But the excitement rose significantly because 2 important papers were published, one written by R.M. White and F.W. Voltmer, and the second by Bleustein.

The start of the SAW adventure

Ruppel:

The SAW adventure start with the development of matched filters for pulse compression! Could you please detail the most important papers from the early days of the development of SAW technology!

Maerfeld:

The first paper is:

R.M. White and F.W. Voltmer “Direct piezoelectric coupling to surface elastic waves”, Applied Physics Letters, vol. 17, pp.314-316, 1965[1]

I am still very impressed by the impact of this paper which became the origin of an industry. The article is short: 2 pages only. It is hard to imagine that before this paper, launching a surface wave was quite tricky. The best known method was a wedge transducer. A bulk wave transducer bonded to a solid having a given angle with the surface of the solid where you expected the surface wave to propagate!

The direct coupling of an electric signal to a Surface Acoustic and vice versa changed the face of the world: the transducer is no more machined, but printed exploiting the photolithographic processes used in semiconductors, meaning high reproducibility and low cost. It means also no extra money was necessary to develop this printing technology. And effectively we kept using second hand equipment from semiconductor industry.

It means also that the surface is accessible for placing as many taps as you need for signal processing (transversal filters) and so having a great facility to implement the impulse response required for your processing. I have the feeling that Dick has not been rewarded correctly for his contribution. He is a simple and humble man more interested in photolithographic process than in signal processing. And he is also at the origin of another industry the micromachining engines or MEMS.

In a very short period of time, many teams switched their research to SAW. The community discovered all the possibilities related with this technic. To be able to exchange ideas lots of conferences, seminars, workshops... were organized. It was like a blast.

Other important papers and inventions in the early days of SAW technology are:

  • Tancrell et al [2] developed a dispersive delay line with an interdigital transducer which periodicity changed gradually from one side to the other side.
  • P. Hartemann et E Dieulesaint[3] weighted the electrode length of this type of filter for reducing the side lobes of the compressed pulse
  • Eric Ash[4] proposed a grating structure for reflecting the SAW and made the first SAW resonator.
  • Marshall et all[5] invented the multistrip coupler.
  • G. Kino et all[6] proposed an analog convolver computing analogically the convolution of 2 different signals.

One key analysis had not been published by the same way, but was written as a patent, the authors of which were P. Hartemann and E. Dieulesaint. The patent claimed that to make a bandpass filter you only have to print a transducer in form of the impulse response of the filter. I never thought it could be a patent since it is always the case: due to excitation mechanism, the form of the transducer is the sampled image of the impulse response of the SAW device. It could have been an excellent publication. However, the patent was recognized as legal and allowed the Company of those authors to receive royalties.

The excitement was maximum. The number of papers presented at the IEEE Symposium on Sonics and Ultrasonics exploded and this conference became the annual meeting of the SAW Community.

Ruppel:

Next important development of SAW technology is related to different wave types, which finally enabled microwave acoustic filters to be used in the RF stage of cellular phones. Could you please detail your view on this development!

Maerfeld:

Let me talk about New Shear Waves.

The second paper, more academic, written by Bleustein,[7] claimed the existence of a new shear wave propagating on the surface of some piezoelectric material. The discovery of a new acoustic wave was an exceptional event and during all the SAW conferences, workshops, Seminars, etc. the discussions were always coming back to that subject.

Once in a workshop held in Aviemore (Scotland), I met a young and slim Russian called Youri Goulyaev who considered himself as a theoretician. He was very often joking with the French attendees of this meeting since he had just spent one year in Paris making some research at the “Ecole Normale Supérieure”. He was claiming that he published the existence of this pure shear surface wave first, sooner than Bleustein but in a Russian Journal, and only published in Russia.

At that time, I had been charged by P. Tournois to try to make an amplifier using the acoustoelectric effect in semi conductive piezoelectric materials and we decided to try this with a so called Bleustein Wave. I observed a strong effect, higher than with a Rayleigh wave although I could not compensate the insertion loss of the transducer. We decided to present the result at the next Symposium held in San Francisco.

I prepared the following title for my presentation: “Bleustein surface wave amplification in CdS”. Before giving my talk, I met Youri again who was extremely critical with my work. I tried to understand why. And finally, remembering Aviemore’ discussions, I changed my title into “Bleustein-Gulayev surface wave amplification in CdS”. I was immediately rewarded by Youri who declared my presentation excellent and referred to this paper as the first experimental demonstration of his “wave”. The paper was published in “Applied Physics Letters” with the same new title.

Since then, this wave type has been called the Bleustein-Gulyaev wave.

Ruppel:

Please tell me about the Maerfeld-Tournois wave!

Maerfeld:

One day, Tournois came into my office.

“Since the piezoelectricity effect has modified the existing domain of a surface acoustic wave, don’t you think that similar effect could occur for an interfacial wave a so-called Stoneley Wave?”. One hour later, I went into Tournois’ office: “It is obvious, I said, take a 6mm crystal like CdS.; split it into 2 pieces by a face containing the C axis. Turn one piece 180° in order that the 2 C axes become aligned in opposite direction and then stick the 2 pieces together, then there is a shear surface wave propagating guided by this interface”. And I illustrated my talk by joining my 2 hands with the thumbs pointing in the same direction. And just after I turned one hand in order to have the thumbs in opposite direction. “There you have an interfacial wave” I said. “You should demonstrate it” he said.

To write down the equations probing the existence of this interfacial wave was very straightforward, and the same day we wrote the entire paper and sent it to “Applied Physics Letters”. The reviewer corrected some bad English spelling or sentences and it was published rapidly.[8]

And then, for 2 or 3 years we did not hear anything about the paper. So, I concentrated myself on the study the Marshall multistrip coupler (MSC) and developed a convolver using a MSC beam compressor which I invented.[9]

Later, we learned that Bert Auld, from Stanford University, was writing a book on Acoustics. He appeared to be deeply interested in this interfacial wave. He taught it to his students and named it the Maerfeld-Tournois Wave. The name was accepted by the Community.

The birth of an industry

Ruppel:

With all these achievements, the basis for starting the SAW industry was set!

Maerfeld:

The explosion of numbers of searchers produced a very sharp growth in the number of publications, but it was not sterile at all: in a relative short time, the SAW components were introduced in systems. Mainly in 2 applications: pulse compression in radars and IF filters for TV!

Let’s start with pulse compression in radar applications.

It should not be forgotten that at the end of the sixties, the so called “cold war” between western and communists countries was at its paroxysm. In 1968, the Soviet Union invaded Czechoslovakia. So, lot of efforts were made to improve electronic warfare performances. Pulse compression radar suggested by specialists of signal processing, was made possible and efficient thanks to the SAW technology. Many types of dispersive delay line were produced using not only interdigital transducers but also reflective arrays of grating on the surface and Love waves. All the RADARS, on ground, airborne or in satellite started to use SAW devices.

Next came IF filters for TV sets!

To select a TV channel, a filter is necessary in the IF (Intermediate Frequency) band. At that time, these filters required a relatively high number of cells made of coils and capacitances. The filter occupied a whole PC board. Furthermore, this technology suffered from some instability of the coils.

As soon as engineers were able to synthetize the required filter on a single piezoelectric crystal, the mass production of it started. The planar lithography technology had been developed for the semiconductor industry and was fully available for the SAWs, the same for automatic assembly or pick and place machines. The only specific necessary development was to get large enough mono crystals of quartz or lithium niobate. A few companies were able to develop the technology and 3 inch crystal wafers were soon available.

Thus, IF TV filters started to be mass produced.

Analog versus digital computers

Ruppel:


SAW technology allowed devices with high time band width product! Therefore, engineers worldwide started thinking and researching about using SAW devices for signal processing.

Maerfeld:

To put this evolution in perspective, I usually express the SAW performances in digital specialist’s language. This approach was published in the 80’s by H. Gautier and P. Tournois[10] who made a detailed comparison between SAW and microprocessors. A SAW filter, either a dispersive one or a band pass one, give the convolution of its impulse response with the incoming signal. If B is bandwidth of the impulse response and T its duration, a digital computer would have to operate at least 2BT multiplications plus one addition to get one point of the convolution function. The filter does that in a time 1/B. Therefore, the equivalent digital operator must have a power of 2B2T FLOPS. If I take an example a dispersive delay line having a BT product of 1000 and a 100 MHz bandwidth it gives you a minimum microprocessor power of 200 GFLOPS. At the end of the seventies, beginning of the eighties the power of the microprocessors were 3 or 4 orders of magnitude lower than that.

By extending Moore’s law over a long period of time we predicted that the IF filters would only become non-competitive around the year 2000. That meant, that we had 20 years of IF business in front of us! Unfortunately, Moore’s law happened to be accurate and after the year 2000 most of the IF applications for SAW devices vanished.

A project of the 80’s illustrates that: The NATO considered that the IFF (Interrogation Friends and Foes) used at that time was not performing enough. Most of the losses of the Israeli aircraft fighters during the last war occurred when returning to their bases. A project was built to spread the IFF signal on a large bandwidth so that the signal level would be far below the noise floor and could only be detected by a friend having the appropriate demodulator. The ambition was so high, that in their view, only the beam width compressor convolver I had developed could be used. So, discussions started to get the patent as available as possible for the NATO members. But at the end, the project was modified and the ambition reduced by 2 orders of magnitude so that pure digital technology could be used and the contract we had, stopped. In 1981, a new French government went to power with 4 communist ministers. Was there a link?

Come back to my career

Ruppel:

Let’s continue to talk about our career!

Maerfeld:

As I said sooner I joined a signal processing research group led by P. Tournois and composed of 2 branches one for analog and the second for digital processing. In less than 5 years, the digital group moved to get closer to the rest of the Sonar developers and we stayed isolated. It appears that the work we were doing was more useful for the radar rather than for the sonar division of our Company. Then started a curious situation (It was such all along my career), of being in a group considered as producing key components for the Company but not for the division I was in. The only reason to stay in the Sonar division (if you do not take into account the location of this division on the French Riviera) was the fertilizing environment of acoustic and signal processing. I am also very grateful to the managers of this division who protected me and my group all the time.

But it was necessary in gratitude to accept missions out of the SAW domain. In the mid 70s I was asked to take in charge the antenna group of the sonar division who was encountering serious difficulties. I mention this event because I promised the management that we would develop a simulation program with which we would be able to anticipate accurately the performances of the antenna avoiding the difficulties we faced before. And so, before the end of the seventies, we developed a Finite Element Program for the design of bulk wave transducers. And of course, we used it for the SAWs later on.

Then the general manager of the Thomson CSF asked to help the medical ultrasound subsidiary which appeared to be beyond the competition. So, we developed multiple transducer arrays called electronic probes for ultrasound scanners. After having fixed the problem and a good engineer to head the antenna group had been hired, I asked to come back exclusively to the SAW activity and to keep the medical probe developers in my group.

So, at the beginning of the 80’s I was head of a group making strategic components for other subsidiaries of my mother Company, Thomson CSF. We were not allowed to sell our components outside the Company. At the end of the 80’s the situation was completely reversed and we were pushed to sell in OEM in order to reduce the cost of maintaining alive a structure producing key components.

This type of missions out of the SAW activity happened twice after this one: In 1982, I was managing director of the ultrasound scanner subsidiary and in 1989 I had to take in charge the airborne sonar division near Paris. Each time, I came back to the SAW activity

The 80s

Ruppel:

What happened with SAW technology in the 80s! Please give me your view on the development!

Maerfeld:

For me, the 80’s had been transition years. Pulse compression radar with SAW delay lines were in production. So, we were producing and delivering them. And the production of IF TV filters was growing. However, the SAW convolver story for IFF seemed to become the rule. In all the new development of radars, the designers were trying digital processing technics rather than using SAWs. The achieved performances in term of range were lower but the designers claimed to have more versatility in having multiple waveforms for example and so on. We tried to promote the SAW oscillator, trying to prove that starting from a higher frequency clock, the noise floor at mm frequency would be lower, with no real success.

Finally, the decline of the use of SAW devices for pure signal processing seemed to be inexorable. But manufacturing them would last at least 1 decade and perhaps one more if you took into account the maintenance needs.

In my view, during the 80’s 2 events modified the nature of the SAW market.

One is a key milestone in human history, the second more local but important for us:

The first one is the fall of the Berlin’s wall.

The important consequences were a big change on the threats facing the Western Countries. It pushed the staff headquarters to redefine all the priorities and therefore, the need of components.

The second one is as follows:

In the mid 80’s (in 1983 or1984) the French Telecom Administration realized that France was far behind the USA in regards to cellular telecommunication. They wanted to react and to fill the gap. So, they built up a task force. It was called in French: le Groupe Spécial Mobile (GSM). The members of this group were very smart and ambitious. They decided to propose a digital transmission technic (the RF signal transmitted is made of successive bits + or - and to make all the trade-off necessary to get a phone highly mobile. When they were asked why a digital transmission technic, the answer was: “because by using analogue transmission, the network will be saturated” and immediately after we asked if the network was presently saturated, they said “not at all”.

To grant that all the necessary components would be available for the project, the French administration launched an invitation to tender. So, we started working on the component needed for the receiver of the mobile phone. 2 types of filters were in the circuit: the RF one and the IF one. But it was very clear that both could not accept high insertion losses even the IF one.

Fortunately, solutions were proposed. After trying the 3 phase-transducer technology we decided to concentrate on the SPUDT recently proposed by Hartmann et all.[11]

Before the end of the 80’s we knew that both a low loss IF filter fulfilling all the requirement of the band shape and a RF filter were easily feasible. Then I had to promise that my company would mass produce it. So, I did promise. But, at that time, it was a lie. Thomson CSF in 1988 claimed to be concentrated only on electronic warfare and would never let me invest outside this field.

Other SAW applications of the 80’s

Ruppel:

At the end of the 80s the decline of the defense market for SAW devices was visible. Which new applications did you look in?

Maerfeld:

Facing the forecasted decline of the defense SAW market, we had to look how we could replace it. Among those applications suggested in the 80’s, I selected those ones:

SAW sensors

I did not believe in the future of SAW sensors. The reason is not that they won’t perform well or their price would be excessive. The main reason is always the same: If it can be done on a slice of semiconductor and precisely on silicon, it will be done like that even if the performances are lower.

I make a strong exception for the SAW thermometer when associated with the tag technology.

SAW microbalance for measuring chemical or biological reactions

The idea is quite simple: the center frequency of a SAW oscillator implemented on the surface of a crystal is directly linked to the surface wave velocity. The latter, is changed by extremely thin deposition of matter on the surface. So, by measuring the frequency shift you get an information of the surface chemical modification. It is easily shown that the frequency shift is related to the mass of the material fixed on the surface. It is why, the device is called a micro balance. You can measure for example a biological reaction of a specific antigen. They are other means than the SAW of making a microbalance, and once again, if it is possible to implement it on a Silicon wafer it will be done that way. However, by associating the microbalance and the SAW RF technology of the SAW Tag you get a contactless sensor able to suffer severe environmental conditions.

SAW ID Tags.

Even today the SAW ID tag has specific advantages not achievable by semiconductor tags. First of all, it does not require any battery so you can use it for a very long period of time or put it in an out of reach position. And second its sensitivity is extremely high, so you can detect it at a long distance. For example, as used as a toll ticket on a motorway, the vehicle can be checked while running as fast as 80 km/h.

So, to explore those fields was very tempting. But finally, the telecom adventure appeared to be so demanding, that it was completely impossible to divert forces toward them.

The 90’s

Ruppel:

Let’s continue with the 90s!

Maerfeld:

The French administration and the “Groupe special mobile” made an excellent job. They managed to put the European label on the project: GSM became the European standard of mobile telecommunication, placing the European electronic industry in a leading position worldwide. Who dares to say that the European Community is useless?

For my unity, the time of investments had arrived. We had no capacity to produce great numbers of low cost filters. But, Berlin’s wall had fallen a few years before, and now the priority in Thomson CSF was on “dual” activities. Dual means an activity embracing both the military market and the civilian one. SAW used to be in the military market, so in entering a big civilian market I was doing what the top management required. I got easily the money to invest. My former lie turned to be a perfect accomplishment of my promise.

Everyone knows that the GSM was and is a tremendous success. During almost one decade our activity grew by 40% a year, that means to double the sales every 2 years.

For all the SAW community, it was a second birth of the SAW business. During this period, as usual, all the market analysis turned to be wrong, but the error was not the common one. In fact, the reality was always beyond expectations.

But, within Thomson CSF, the SAW activity could no longer stay inside the Sonar division. A Subsidiary was created, named Thomson Microsonics and later Thales Microsonics, more simply named “TMX”.

The heart of TMX

Ruppel:

Creating a subsidiary for SAW devices was a necessary step!

Maerfeld:

The success of TMX in the telecom market was primarily due to the group of engineers who designed the filters. As said earlier, most of the properties of a SAW device is coming from a mask (or a group of masks) from which you reproduce the shape of the electrodes. The design of this electrode array shape is essential.

Furthermore, the SPUDT technology as well as the resonator filters one are not pure transversal filters.

We needed first to have an excellent simulation program able to predict as accurately as possible the technical characteristics of the filter to be developed. This is the foundation on which you accumulate knowledge. Of course, other software had to be developed to synthetize the electrode shape and so on. But it appears essential to be able to test your ideas by an excellent simulation program.

The basic structure of TMX simulation program is due to Jean Desbois. It was never published. He used a matrix approach, he called it the “mixed matrix”, giving the relationship between electrical and acoustical values of 3 port basic structure: 2 acoustic gates and one electrical. The result of the whole array was given by matrix multiplication of each individual cell. The quality of the model is entirely due to quality of the definition of each element of this matrix.

We made all our efforts to improve all the time the quality of the simulation. For example, we developed Finite and Boundary Element Method (FEM-BEM) or used of Green’s functions for that purpose.

The group in charge of developing this model grew around Jean Desbois. But Jean was only a spiritual leader not a managing chief. For the other aspect, a strong group was formed. I will not quote all the name of the key people who joined this group in order to avoid to miss one name. They were in charge of the mask design. Hierarchically, Jean was a part of this group.

I took special care in recruiting for this group and in training young engineers who joined in.

I was very pleased by the attitude of this group: they worked collectively, they were innovative and it was easy to incorporate new engineers as well as senior or famous ones.

The strongest request had always been to reduce the size of the filter. Size reduction means cost reduction. In this aim, the incorporation of resonant structures inside the transducer the so called the RSPUDT[12] was a major achievement of the team.

The Team

Ruppel:

I am sure that you remember many of your excellent engineers in your team! Let’s talk about the most outstanding engineers!

Maerfeld:

It is hard to tell who was more important. I was so happy to have a group working really like single team.

They all brought a part of our success:

I can quote:

Jean Desbois, Marc Solal, Jean Michel Hode, Pascal Ventura, Pierre Dufilie, Stéphane Chamaly

later: JF Gelly, Peter Wright, Victor Plesski

Martine Doisy, Pierre Alexandre Girard, Xavier Perois, Raphael Lardat.

Jean was at the origin of our basic software, he promoted a mix matrix method to predict the response of the filter, as well as our first model of synthetizing, the length, and the position of each electrode. The mixt matrix appeared to be the key stone of all our software. Pascal Ventura and Marc Solal, were at the origin of our Resonant Single Phase Unidirectional Transducer. Jean Michel organize the whole. All the others contributed efficiently.

But, I would like to stress a key and surprising experience:

Jean Desbois was more a theoretician. He worked very slowly, but very thoroughly. Pierre Dufilie, was innovative, very practical, and very performance oriented. Jean did not speak any English. Pierre could not say a single word in French. However, they understood each other. Pierre was able to transform Jean’s theoretical ideas into a practical and performing device. I have no idea on the way they communicated: it was black magic!

IUS 1994

Ruppel:

Tell me more about your activities inside IEEE on S&US!

Maerfeld:

I was elected at the AdCom in 1989. The only problem was that a few days before the election, I was asked to take care of an Airborne Sonar Department in Paris and to leave the SAW activities. I was very embarrassed. Finally, I decided to honor my elected responsibility and attended strictly all the AdCom meetings. It was not so difficult, since the main project of this Department was to try to win an airborne sonar contract from the US Navy and therefore I had to visit our American partner in Los Angeles regularly.

During those AdCom meetings I tried to promote the idea of holding the Symposium outside US. If other sections of IEEE had held, indeed, in some occasion, their Symposium abroad, it had never been such with Sonic and Ultrasonic. The main fear of the AdCom members was that too many US companies would refuse to send their researchers far away, for cost reasons. Finally, the AdCom voted a resolution asking me to make a proposal for a Symposium held in France. At the following meeting, I proposed Cannes for 1994 with Gérard Quentin as General Chair, since I had the feeling that in my position I would not be able to divert enough time to hold the position of General Chair. Therefore, I restricted my part to the local arrangements. It was accepted. Gerard accepted the Chair but did not help me much for the organization.

One important difficulty laid in the imposed format of the meeting. It was asked by the AdCom to select a hotel with enough rooms for the attendees and offering, for free, the required numbers of conference rooms. “We refuse to pay the rent of a Conference Center”, I was told. This type of organization was not common in France and most of the conventions were held in convention centers with separate recommended hotels.

I found only one hotel fulfilling this requirement: Hotel Martinez in Cannes, and this palace was available in November 1994.

Hopefully, we won the contract from the US Navy, and I could come back to the SAW activity and the creation of TMX before the Cannes Symposium.

I was far from anticipating all the difficulties I would have to face!

The first came from the success of the idea: despite all the AdCom member fears, we received much more abstracts than expected (about 20% more) and the technical committee asked to add one extra parallel session for avoiding being forced to reject too many papers. It meant extending the limits of the Hotel capacity! We rented a “marquee” to hold a poster session around the hotel swimming pool!

The second incident was:

During the meeting a special event, a big Dinner Party is to be organized. For that, I contracted a Cruise Company who promised to offer a fine dinner with an orchestra during a cruise in the Bay of Cannes. Unfortunately, 3 weeks before the Symposium, I received a phone call from the Judicial Court of Grasse claiming that this Company was in bankruptcy and that the Court had ordered to stop all its activity immediately. No other Cruise company in Cannes or Nice could provide that service. I found one in Saint Tropez who accepted to do something, but its Ship was much smaller than the one of the first contracted Company. And as you may imagine we had a record number of bookings for this special dinner. So, we decided to split the Party in two successive evenings and we hired a small music band for the 2 days.

But the worst was to come!

Usually, in our region, the weather in November is very sunny and mild. Not in 1994. It started raining at the beginning of October, and it went on for weeks and weeks. We had a bright interval on the first day of the Symposium, but on the second day, the rain started again and the cruises took place in very wet conditions. However, the Symposium went smoothly to its end, with its record number of papers and sessions.

We had organized a tour on the Saturday following the end of the Symposium. We filled up two buses with attendees. On that very Saturday, it did not rain, it poured, it was a downpour, all day long. Such an amount of water falling on a ground saturated by weeks of rain had a very clear effect: Tremendous quantities of water swept down the mountains and converged to the river which became HUGE. After having visited Monaco, Eze, and the “Corniches”, the busses came back to Cannes. One bus managed to cross the Var river just before this river overflowed the motorway. But the second being delayed for some reason was blocked on the left bank of the river and its passengers could only reach Cannes very late in the evening, by train.

The Nice Airport is just located at the mouth of the Var River. For the first time (and the last one till now) in its history, it was flooded. The computers were covered with mud, completely useless. Therefore, the Authority could not control the air traffic and had to close the Airport for one week at least. The attendees who had decided to stay one day more after the symposium for touring reasons were stuck in Cannes.

We spent the following days helping people to reach by train or by rented cars the other nearest airports: Marseille, Lyon or Paris.

This type of weather conditions has never happened in Nice since!

After these events, we were totally exhausted and ashamed, such a bad experience happening for the first symposium abroad!

Hopefully, despite all that, most of the attendees considered this symposium as a success and the AdCom decided to renew the experience abroad on a regular basis.

The end (of my career)

Ruppel:

The end of your professional career was a little bit disappointing for you! Would you like to share some of your impressions?

Maerfeld:

At the end of the 90’s TMX activity was no longer dual, the electronic defense part was very small compared to telecom and medical probe activities. It could not stay inside Thales Group (the new name of Thomson-CSF) anymore. I disagreed with my management on the way TMX should take to leave Thales. The first crisis in the mobile market happening in 2001, weakened my position, and I had to leave the Company even before presenting a joint venture project ready to solve that.

I still disagree with the decisions taken by my successor. For me, what he did turned into a sheer disaster.

Is there any future for the SAW/BAW industry?

Ruppel:

For sure SAW industry has a future today! Do you see applications beyond cellular phones having high potential for the SAW industry?

Maerfeld:

The answer is easy for RF filters for mobile phones. The volumes are growing every year, due to increase number of RF frequency bands, and the introduction of carrier aggregation”

But I do think that some other SAW activities could have a future, even in the consumer market as for example:

The SAW thermal sensor:

For me there is still some specific advantage for this technology compared to semiconductor sensors. It is the possibility to be read contactless, remotely using the SAW tag technic without battery. And you can read simultaneously a large number of sensors. This is clearly demonstrated in the professional business for some difficult environment (Temperature control of the electrical power network for example). But even in the consumer market, SAW sensors are small, rugged and do not need any battery. I do not understand why they are not used on large scale.

The bio sensor:

It is same point in fact, i.e. the delay time of the wave crossing the reaction area can be measured remotely or contactless without battery and this is for me a key advantage.

The SAW RFID.

Clinton Hartmann demonstrated the advantages of the SAW RFID. Indeed, it suffers from a lack of flexibility, but its sensitivity is largely greater (the device can be detected at a range of a few tens of meter, instead of a few tens of centimeter), and it does not require any battery. For a long time, I thought that the SAW RFID would be used for the protection of masterpieces of Art. Precisely, if you manage to imbed a SAW label in the valuable object, you would be able to read the label remotely without trying to take it out (in fact without knowing where it is embedded) and for the eternity. And we have up to 1016 different codes available. Therefore, the identification will be certain. I already patented an acoustic seal to detect if someone had tried to remove the SAW label.

Late Career

Ruppel:

How was the transition to retirement?

Maerfeld:

I do not like to speak about that period. I tried to develop a start up in ultrasound imaging based on studies started in TMX. But Thales management did not help.

Retirement

Ruppel:

Do you still have contact with your friends in the SAW community?

Maerfeld:

Of course, from time to time, I meet former colleagues from TMX.

You know that TMX collapsed two years after I left.

Different parts are still alive but separately. One group is working on SAW sensors and succeeds to develop thermal SAW sensors used in very hard environment and particularly in the development of a new generation of power distribution known as “smart grids”. A large number of designers joined your former group of EPCOS, which became NTK and more recently a part of Qualcomm. And finally, the medical probe group was acquired by GE. They are still located here in Sophia Antipolis. Surprisingly, the SAW designers and the ultrasound probe team are in the same building (but different from the one we were at TMX). For me, it is easy to visit both

Other individual engineers were engaged abroad and particularly in Orlando.

Our relationships with some other members of the SAW community are very strong like the one we keep with Eric Ash and Gerry Farnell’s families.

But we are getting old and some close members left us such as Pierre Tournois, Gerry Farnell or Clinton Hartmann.

Ruppel:

We did not talk about your family! Could you please tell me a little bit more about your family?

Maerfeld:

You have already met my wife, Emma. We have been married for more than 50 years (we celebrated our gold wedding almost 2 years ago). We have 3 children, 2 girls and one boy. They all have children so we count 7 grandchildren. We enjoy visiting them and since they are living in different parts of France we cross regularly this country, driving back and forth from Nice to Nantes or Quimper, stopping in Paris. Fortunately, 2 of our grandchildren live in Nice and we can meet them more often.

Short bibliography

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  3. P. Hartemann, E. Dieulesaint. “Intrinsic Compensation of side lobes in a dispersive acoustic delay line”. Electronics Letters,5, p 219- ,1969
  4. E.A. Ash “Surface Wave Grating Reflectors and Resonators”; Proc. IEEE G-MTT, pp. 385-386, 1970
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  8. C. Maerfeld, P. Tournois, ”A pure shear surface wave guided by the interface of two semi-infinite media,” Applied Physics Letters Vol. 19, n°4, pp. 117-118 (1971)
  9. Ph. Deranould, C. Maerfeld. “Acoustic Convolver Using Multistrip Beamwidth Compressors”, Electronic Letters, vol. 10, n° 11, pp. 209-210 (1974)
  10. H. Gautier, P. Tournois, "Very fast Signal Processing as a result of the coupling od Surface Acoustic Wave and digital technologies,” IEEE Trans. On Sonics and Ultrasonics, 28 (3), 126-131, (1981)
  11. C.S. Hartmann, P.V. Wright, R.J. Kansy, E.M. Garber: “Analysis of SAW interdigital transducers with internal reflections and the application to the design of single-phase unidirectional transducers”, Proceedings of the IEEE Ultrasonics Symposium, 1982, pp. 40–45
  12. P. Ventura, M. Solal, P. Dufilie, J. M. Hode and F. Roux, “A new concept in SPUDT design: the RSPUDT (Resonant SPUDT),” IEEE on Sonics and Ultrasonics Proceeding, pp. 1-6, 1994.