Tools for High Performance Computing 2015 Proceedings of the 9th International Workshop on Parallel Tools for High Performance Computing September 2015 Dresden Germany 1st Edition Andreas Knüpfer
Next-Generation ADCs, High-Performance Power Management, and Technology Considerations for Advanced Integrated Circuits: Advances in Analog Circuit Design
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Contents
Preface
Acknowledgement
Author biography
Introduction
The story of BA Flight 9—From the Introduction to the 1st edition
A few questions to Andrew Townley-Freeman
1 Introduction to MEMS and RF-MEMS: from the early days of microsystems to modern RF-MEMS passives
1.1 Introduction to semiconductor and microsystem technologies
1.1.1 The genesis of MEMS
1.1.2 Micro-fabrication technology platforms
1.1.3 Applications of MEMS sensors and actuators
1.2 Introduction to RF-MEMS
1.2.1 Switches and simple passives in RF-MEMS technology
1.2.2 Complex reconfigurable passives in RF-MEMS technology
1.3 Conclusion
References
2 Expectations versus actual market of RF-MEMS: analysis and explanation of a repeatedly fluctuating scenario
2.1 General considerations of the market in the technology sector
2.2 RF-MEMS on the market: vision of the early days
2.3 Fluctuating RF-MEMS market forecasts
2.4 Analysis of RF-MEMS market expectations (disappointment)
2.4.1 Intrinsic factors
2.4.2 Extrinsic factors
2.5 The RF-MEMS market
2.5.1 Evolution of the market in recent years
2.5.2 The market situation today and its future perspectives
2.6 Conclusion
References
3 The 5th Generation (5G) of mobile networks: challenges and opportunities of an impelling scenario with an outlook on the future 6th Generation (6G)
3.1 General considerations on mobile telecommunication networks
3.2 Evolution of mobile standards and services
3.2.1 The 1st Generation—1G
3.2.2 The 2nd Generation—2G
3.2.3 The 3rd Generation—3G
3.2.4 The 4th Generation—4G
3.2.5 Wrap up of mobile standards from 1G to 4G
3.3 The 5th Generation—5G
3.3.1 Massive MIMO
3.3.2 Interference management
3.3.3 Spectrum sharing
3.3.4 Device-to-device communication
3.3.5 Millimetre-wave solutions
3.3.6 Cognitive radio
3.3.7 Massive centralised RAN
3.3.8 Vehicular communications
3.3.9 Network slicing
3.3.10 Other technologies
3.4 Beyond 5G—an outlook on the emerging trends and early visions of the Artificial Intelligence (AI)-driven 6G of the future
3.4.1 A brief overview of 6G and Super-IoT/TI current visions
3.4.2 Emerging technology trends driving 6G
3.4.3 Potential limiting factors to the full disruption of 6G
3.4.4 Possible novel approaches to empower 6G
3.5 Conclusion References
4 RF-MEMS passives for 5G applications: case studies and design examples
4.1 An introduction to RF passives’ specifications trends in 5G
4.2 A few notes about the RF-MEMS technology platform
4.3 Electromechanical simulation of RF-MEMS devices
4.3.1 Static structural simulation of the pull-in/pull-out characteristic
4.3.2 Transient dynamic simulation of the switching (opening/closing) time
4.4 Electromagnetic simulation of RF-MEMS devices
4.4.1 Finite Element Method (FEM) analysis
4.4.2 Modelling based on equivalent lumped-element networks
4.5 Conclusion
References
5 A comprehensive approach to the compact multi-physical modelling and simulation of RF-MEMS
5.1 Introductive considerations on the compact modelling approach
5.2 Developed models and software library implementation
5.2.3 Mechanical constraints and force/displacement sources
5.3 Examples of library validation and exploitation in 5G-relevant RFMEMS components and networks case studies
5.3.1 Electromechanical and RF validation of a clamped–clamped RF-MEMS shunt switched capacitor
5.3.2 Electromechanical and RF validation of a clamped–clamped RF-MEMS series ohmic switch
5.3.3 Electromechanical validation of a cantilever-based RFMEMS series ohmic switch
5.3.4 RF simulation of a multi-state RF-MEMS power attenuator
5.4 Conclusion References
Appendix A Moving MEMS: Dynamics down in the micro-world
Appendix B How to set up, configure and exploit the MEMS behavioural models software library
This book is dedicated to the people below, without any relationship between the order of appearance and their relevance.
To Brando and Pietro and to their relentless energy and unconditional serenity, with the profoundly heartfelt wish of conserving such treasures to the largest and longest possible extents, across the extraordinary and endless journey unrolling ahead their limpid eyes.
To Moira, for making her way, our way, relentlessly, day after day, in spite of our adversities.
To Rossana and Pietro, with endless gratitude for their unconditional presence and for making everything possible.
To Luisa De Sanctis, in the awareness that wherever she is now, she is beautiful as always.
To Victor Manuel Caraballo, in the awareness that wherever he is now, he is dancing and smiling.
Jacopo Iannacci
Preface
The scientific area of microsystems, known as Micro-ElectroMechanical Systems (MEMS), has followed an evolutionary path intimately linked to that of semiconductors, albeit with relevant differentiation. MEMS and semiconductor technologies developed together, starting in the 1960s. While the manufacturing process of transistors was becoming more sophisticated, critical fabrication steps, like the patterning of buried conductive/piezoresistive thin-films and deposition of metals, began to be ventured to yield microstructures with mechanical properties. However, if transistors and semiconductors followed a relentless trend to miniaturisation (More Moore) across the last five decades and more, microsystems developed increasing and diversifying transduction principles, aiming at broad functionalities in the fields of sensors and actuators (More than Moore).
Within the scenario of microsystem technologies, RF-MEMS, i.e. MEMS for Radio Frequency passive components, started being investigated in the 1990s. Passive components for RF applications, such as waveguides, micro-relays, variable capacitors (varactors), as well as tunable filters, reconfigurable phase shifters, impedance tuners, and so on, were demonstrated in the literature. Their characteristics, in terms of low loss, high isolation and wide tunability/reconfigurability, were outstanding if compared both to standard RF/microwave components as well as to semiconductors.
Such remarkable performances triggered, in the early 2000s, inflated expectations around the massive absorption of RF-MEMS components in mass-market applications, especially referring to mobile handsets, which were growing particularly fast in those years, with the 2nd and 3rd generations of mobile communications (2G/3G). In actuality, market forecasts were systematically disappointed for more than a decade, and the foreseen revolution never took place.
More recently, starting from 2014, RF-MEMS commenced making their way into the market landscape, thanks to a need that other technologies
were unable to address effectively. Modern 4th generation (4G) smartphones, due to the integration of more and more components, triggered a degradation trend in the quality of communication, which has been mitigated by the wide reconfigurability of MEMS-based RF passives. As a result, adaptive impedance tuners are now the first successful example of the exploitation of RF-MEMS technology in the consumer market segment. Besides, other MEMS components, such as high-performance switches, are starting to consolidate in applications like high-linearity RF Power Amplifiers (PAs) and RF Front Ends (RFFEs).
If this is the quite reassuring recent market snapshot of RF-MEMS, in addition the 5th generation (5G) of mobile communications and services has begun to be deployed in the last few years. Despite the fact that 5G is stepping in compliance with the 4G Long Term Evolution (4G-LTE) and according to a smooth fashion, it will pursue fundamental drivers of network densification and diversification. Compared to 4G-LTE, the full deployment of 5G in the years to come will demand an increase of data volume, up to 1000 times, of connected devices, from 10 to 100 times, as well as reduced End to End (E2E) latency, massive Machine-Type Communication (mMTC) and operation in the millimeter wave (mm-wave) range.
Further ahead, 6G is already starting to gain shape, capitalising on the visions and high-level Key Performance Indicators (KPIs) that are being elaborated in the scientific literature. Keeping as reference the year 2030, 6G is expected to take over 5G, marking a further 1000× increase in terms of data rate and speed, apart from largely increased reliability of communications, and, most of all, massively leveraging Artificial Intelligence (AI) to trigger resilient and self-evolutionary network paradigms.
These harshly stringent system requirements will push for very-highperformance, widely reconfigurable and frequency-agile passive components. RF-MEMS technology holds the fundamental features to be a Key-Enabling Technology (KET) for 5G and future 6G. From a different perspective, 5G/6G could be the killer applicative scenarios for a massive consolidation of RF-MEMS in the mass-market landscape.
The aim of this book is to outline the outstanding intrinsic potential of RF-MEMS technology with reference to future 5G/6G mobile
communications and services. The way this objective is pursued is twofold. On one hand, the proper background concerning the characteristics of RFMEMS is built, together with a definition of target specifications of interest for future telecommunications protocols and standards. On the other hand, practical insight around the design and development of RF-MEMS passive components is provided, by reviewing a few case studies of design concepts, also including multi-physics simulation approaches and techniques. In more detail, the book unfolds, chapter by chapter, as reported in the following.
Chapter 1 develops a comprehensive discussion on MEMS technologies. First, the inception of microsystems is analysed with reference to the evolution of semiconductor technologies, highlighting common features as well as their differentiation. The most diffused technology platforms for microsystems manufacturing are reported. Examples of consolidated (market) exploitations of MEMS sensors and actuators are also provided. Then, RF-MEMS are introduced, explaining their working principles and listing diverse actuation mechanisms. Subsequently, the main categories of RF-MEMS devices are reviewed, focusing both on simple components, as well as on complex high-order reconfigurable networks.
Chapter 2 places the evolution of the RF-MEMS market, since the early days of the technology, under the spotlight. First, fundamental market analysis concepts, like the hype curve and technology push/market pull scenarios, are introduced. Then, the boosted prospects around massive market penetration of RF-MEMS, counteracted, in fact, by fluctuations and disappointments for over a decade, will be studied in-depth. Two sets of reasons, namely intrinsic and extrinsic to RF-MEMS technology, are identified and discussed. Bearing in mind the lesson learned across multiple forecasted and then missed breakthroughs, a sound overview addressing the current state of the RF-MEMS market for mobile applications is provided.
Chapter 3 focuses on present and future mobile communication protocols. Initially, the working principles of mobile networks are introduced. The evolution of services and performance are reviewed, starting from the 1st generation (1G) of mobile communications, launched in the late 1970s, to the 4th generation (4G). Subsequently, the frame of the under deployment and future 5th generation (5G) communications is
depicted. The expected performance and services offered to end users are discussed, along with a comprehensive recap of the current state of its rollout. Concerning the further development of the paradigm, the main drivers of network virtualisation, densification and diversification pushed forth by 5G will also be debated, covering challenges and KETs to make this vision real within a few years. A brief outlook will also be developed on future 6G, with reference to the timeframe of the next decade, highlighting the potential limitations of the current Hardware-Software (HW-SW) systems development approaches in making the current visions turn into reality.
Chapter 4 deals with a few RF-MEMS design concepts, discussed through a quite practical and hands-on approach. First, capitalising on system-level requirements unrolled in the previous chapter, a few classes of passive components and a set of target specifications critical for 5G/6G will be reported. Then, examples of RF-MEMS designs will be studied in detail, with the aid both of electromechanical and electromagnetic multi-physics simulations. Leveraging the aforementioned tools, case study designs will be altered, showing how this influences the RF-MEMS characteristics and how they can be tailored with respect to the requirements.
Chapter 5 builds upon the hands-on modelling and simulation of RFMEMS passive components. To this end, a purposefully developed software library of compact analytical models of basic MEMS structures will be reported and discussed in detail. The tool is based on the VerilogA programming language, and it can be exploited in any commercial or open source Integrated Circuits (ICs) development environment supporting Hardware Description Language (HDL) syntaxes. Apart from discussing the most relevant details of the implemented mathematical models, the chapter will also focus on practical exploitation examples of the mentioned tool, with reference to physical and experimentally characterised samples of RF-MEMS lumped components and complex networks.
Appendix A enriches the book’s content, showing the dynamics of a few RF-MEMS devices by means of experimental videos (acquired through optical microscopy techniques) and simulated animations.
Appendix B completes the book, gathering practical information and hints, according to a user guide fashion, in order to introduce the reader to the practical use of the MEMS compact model library, previously reported in chapter 5, which is also made available for download along with the
manuscript (available at https://iopscience.iop.org/book/978-0-7503-41998).
Acknowledgement
I want to express gratitude to the people below, without any relationship between the order of appearance and their relevance.
Dr John Navas, Senior Commissioning Manager at IOP Publishing, and all his colleagues at IOPP involved in the realisation and production of this book, for their availability and for building together a fruitful working relationship, based on reciprocal trust and esteem, which goes on since the early phase of the 1st edition’s preparation, back in late 2016.
Dipl.-Ing. Harald Pötter, Dr-Ing. Ivan Ndip and all the colleagues with the RF & Smart Sensor Systems Department at Fraunhofer Institute for Reliability and Microintegration IZM (Berlin, Germany), for providing access to the High Frequency Laboratory equipment, necessary to perform the experimental characterisation discussed in chapter 4.
Prof. Dr Gerhard Wachutka, Prof. Dr Gabriele Schrag and Dr Thomas Kuenzig (the latter, now with Infineon Technologies) with the Institute for Physics of Electrotechnology at Munich University of Technology TUM (Munich, Germany), for providing access to the characterisation laboratory and optical measurement facilities, discussed in appendix A.
Jacopo Iannacci
Author biography
Jacopo Iannacci was born in Bologna, Italy, in 1977. He received the MSc (Laurea) degree in Electronics Engineering from the University of Bologna, Italy, in 2003, and a PhD in Information and Telecommunications Technology from the Advanced Research Center on Electronic Systems ‘Ercole De Castro’ (ARCES) at the University of Bologna, Italy, in 2007.
He received the Habilitation as Associate Professor in Electronics from the Italian Ministry of Education, University and Research (MIUR), in 2017, and the Habilitation as Full Professor in Electronics from the Italian Ministry of University and Research (MUR), in 2021.
He worked in 2005 and 2006 as visiting researcher at the DIMES Technology Center (currently Else Kooi Lab) of the Technical University of Delft (www.tudelft.nl), the Netherlands, focusing on the development of innovative packaging and integration technology solutions for RF-MEMS devices. In 2016, he visited as a seconded researcher the Fraunhofer Institute for Reliability and Microintegration IZM (www.izm.fraunhofer.de) in Berlin, Germany, to conduct high-frequency characterisation of RFMEMS components jointly with the RF & Smart Sensor Systems
Department at IZM. Since 2007, he is researcher (permanent staff) at the Center for Sensors and Devices of Fondazione Bruno Kessler (www.fbk.eu), in Trento, Italy.
His research interests and experience fall in the areas of Finite Element Method (FEM) multi-physics modelling, compact (analytical) modeling, design, optimisation, integration, packaging, experimental characterisation and testing for the reliability of MEMS and RF-MEMS devices and networks for sensors and actuators, Energy Harvesting (EH-MEMS) and telecommunication systems, with applications in the fields of 5G, Internet of Things (IoT), as well as future 6G, Tactile Internet (TI) and Super-IoT.
Dr Iannacci has authored more than 100 scientific contributions, including international journal papers, conference proceedings, books, book chapters and one patent. Among them, a few items are going to be mentioned here. The monograph Practical guide to RF-MEMS, published by Wiley-VCH (https://onlinelibrary.wiley.com/doi/book/10.1002/9783527680856), in 2013, was adopted in several courses as a reference textbook. The monograph RF-MEMS Technology for High-Performance Passives—The challenge of 5G mobile applications, published by IOP Publishing (https://iopscience.iop.org/book/978-0-7503-1545-6), in 2017, along with the articles ‘RF-MEMS Technology for 5G: Series and Shunt Attenuator Modules Demonstrated up to 110 GHz’ (https://ieeexplore.ieee.org/document/7556311) and ‘RF-MEMS Technology for Future Mobile and High-Frequency Applications: Reconfigurable 8-Bit Power Attenuator Tested up to 110 GHz’ (https://ieeexplore.ieee.org/document/7726036), published on the IEEE Electron Device Letters (EDL), in 2016, were among the first contributions in the literature discussing the employment of RF-MEMS technology in the frame of 5G applications.
He was and is currently involved in several international conferences as symposium chair/co-chair, session chair, technical program committee member, international advisory board member, tutorial lecturer and invited speaker, among which the following few are mentioned: IEEE Sensors, SPIE Microtechnologies, ESSCIRC-ESSDERC, ESREF, MNDCS.
Jacopo Iannacci is Senior Member of the IEEE (www.ieee.org), and is currently Associate Editor of the Springer Microsystem Technologies (https://www.springer.com/journal/542) and of the Frontiers in Mechanical Engineering (https://www.frontiersin.org/journals/mechanicalengineering#).
Introduction
Driven by my passion for commercial aviation, I wrote the introduction to the 1st edition of this book, back in 2017, around the incident of the British Airways (BA) Flight 9. The text is entirely reported below, right at the end of this section. When the book was launched, after receiving the green light from Dr John Navas at IOP Publishing, on early December 2017, I decided to publish the BA Flight 9 story in a LinkedIn article, entitled ‘A Lesson Transcending Science’, available at the following link: https://www.linkedin.com/pulse/lesson-transcending-science-jacopoiannacci.
Nearly four years later, precisely on September 21, 2021, I received an email of appreciation regarding the LinkedIn article. My reaction was twofold. I was happy to read the message, and I jumped on the chair when I reached its end. The sender was Andrew Townley-Freeman, son of Barry Townley-Freeman, Senior Engineer Officer of BA Flight 9.
Since then, I started exchanging messages with Andrew, led by my curiosity for aviation and not only. Moreover, at that time I was working on the 2nd edition of the book, so I asked Andrew if he was available to answer some questions I would have then included in this Introduction. As a matter of fact, Andrew kindly accepted, so I report below my questions and his answers.
Closing the circle of coincidences, I am writing these words in February 2022, just a few months before the 40th anniversary of the BA Flight 9 incident. This is a further motivation for which I want to express my gratitude to Andrew Townley-Freeman for contacting me, as well as to his father, Barry Townley-Freeman, to Roger Greaves and Eric Moody, Engineer Officer, First Officer and Captain, respectively, of BA Flight 9, for what they did that night of June 1982.
Jacopo Iannacci
The story of BA Flight 9—From the Introduction to the 1st edition
On the evening of June 24, 1982, British Airways Flight 9, operated by the Boeing 747 named ‘City of Edinburgh’, was en route from Kuala Lumpur to Perth, in a multiple stopover haul from London (Heathrow), to Auckland. At around 20:40 (Jakarta time) engine number 4 started malfunctioning and failed straight away. According to standard drills, the crew shut it down and armed the fire-extinguishing system. Shortly after, engine number 3 failed for no apparent reason, followed by engines 1 and 2. In a matter of two or three minutes, all four engines were down. It was the first time in the history of aviation that a Boeing 747 lost all four engines.
Starting from the altitude of the engines’ failure, Flight 9 had approximately 23 minutes of gliding available before unavoidably touching down. Jakarta airport was within gliding distance, but a mountain in between had to be cleared; however, gaining altitude was not an option with no functioning engines. The only alternative was banking towards the open sea and trying an emergency ditching, even though, in the middle of the night and with no functioning engines at all, it was a very risky manoeuvre. On top of that, it would have been the first time that a Boeing 747 was trying to land on water.
After several minutes, just a steps before the point of no return in which the crew would have had to aim the Boeing 747 nose to the Indian Ocean, engine 4 came back to life. Two minutes later, all four engines were back on track. Flight 9 gained altitude, cleared the mountain and landed safely in Jakarta.
The reason for the failure remained unknown until scientific investigations were carried out. The cause was found to be a cloud of volcanic ash produced by an eruption of Mount Galunggung, in West Java. The particles engulfed the engines, killing their power. It was only when the aircraft significantly lost altitude and the engines cooled down, that the ash
solidified and broke off from the fans and rotating parts, allowing them to resume normal operation.
In summary, it was the first time a Boeing 747 had lost all four engines. The crew had absolutely no idea of the reason for such a failure, and found themselves faced with a critical decision: on the one hand, an emergency landing in Jakarta, impossible without engines; on the other, an emergency ditching in the Indian Ocean, at night, with no thrust, attempting a landing that had never been done before with a Boeing 747.
What Captain Eric Moody, First Officer Roger Greaves and Engineer Officer Barry Townley-Freeman kept doing in those endless minutes, was one, and only one thing. They repeated the engines’ in-flight starting procedure, time after time, and even with no response at all, they tried again, dozens of times, relentlessly, without caring about the unmistakeable ineffectiveness and uselessness of their actions; without paying too much attention to the hopelessness of the whole situation.
While studying averted and, unfortunately, in other circumstances, unavoidable aviation accidents, I unexpectedly found an invaluable source of cases from which important lessons can be learned. For instance, what the crew of Flight 9 did in a matter of less than 20 minutes, projected on the unrolling of a lifespan—of course without the pressure of imminent disaster —could be the key to success. Pushing forth and trying to do what one feels like doing, against unfavourable circumstances and adverse and sceptical people, as well as, on top of it all, a lack of confirmation, might be a way to reach the target, because, primarily, it is the proof of your own motivation, belief and passion.
In fact, immediately following landing in Jakarta, Moody, Greaves and Townley-Freeman, instead of having champagne (and celebrating) with the cabin crew and passengers, looked through the booklet containing all the flight procedures and emergency drills dozens of times, because they were concerned that the engines’ failure could have been their fault.
Now, if someone would ask me to unfold the concept of commitment, I think that this example would sketch quite effectively the meaning that such a term bears.
A few questions to Andrew Townley-Freeman
JACOPO IANNACCI (JI): Andrew, as you recently wrote me, you were the person at home picking up the phone call of Berry from Jakarta. Which is the most vivid memory you have of that moment and of the rest of June 24?
ANDREW TOWNLEY-FREEMAN (ATF): I was getting ready to go to my part time job for the evening and the house phone rang—there were no mobiles then—and, to my surprise, it was my father. Probably because the telephone line wasn’t that good, he was speaking very quickly. He said that they had had an incident and when the news breaks, don’t worry, they are all ok! I had to go find mum, who was out shopping, and tell her, and also phone the homes of the Captain and First Officer. I didn’t think much more about it until I got home from work and mum said that British Airways had called her, and there was a little more to the full story. The next morning, I was sent to the newsagent to buy every newspaper!
JI: Did the spread-out of the BA Flight 9 case, on media and among people, interfere on your daily life and on that of your family, in the weeks/months after it happened?
ATF: No, not at all. I think that in those days, news reporting was a lot less sensational and where this would be a massive story in this era, I don’t really recall much being said after the first day or two.
JI: As at the time of this interview it is early 2022, we are very close to the 40 years anniversary of BA Flight 9. Wrapping together these four decades, what is the most relevant lesson you learned, in your personal and/or professional life, from what happened on June 24?
ATF: I don’t know if this is driven by the events of that night, or just the sort of person that my father is in general, but what I learned (especially in my professional life) is that you stay calm and do things the right way. Panicking when things get tough is an unhelpful emotion and wastes time—
you have to put that aside and solve the problem. I think that it has also instilled the value of team working.
Above all, we all know the difference between being professional and being unprofessional, and I strive to be professional every day. My father’s approach to this guides me every day.
JI: Probably I can’t help sticking to the idea that in June 1982 I was barely 5 years old, i.e. in that period of life when my father, police officers and airplane pilots were all heroes. If I think to this and to what I am today, the feeling that a lot of time passed, gets stronger and stronger. Differently, if I think that 40 years ago planes were flying as they are today, it seems like yesterday. Having said this, thinking of all the time gone, and reasoning in very general terms, is there one item that gives you the feeling that a huge time has passed, and something else that, on the contrary, makes you think that the journey from 1982 to 2022 was not so long, after all?
ATF: When the event happened, I was just 18 years old so, on the one hand, it’s (almost) a lifetime ago. Things have changed, especially in flying. Flight Engineers are no longer needed on today’s airplanes and if you look in a flight deck from those days to now, they are hugely different. Closer to your field, when dad called me from Jakarta, they had had to book a telephone line to call the UK and then they were able to call. Today, they would call on their mobile … in fact, the passengers would probably be live streaming the incident!
On the other side, there are things that haven’t changed. When problems happen, we still need quick thinking humans to address them. If we think about Covid, the scientists that developed the vaccines have done a modernday equivalent of the crew of BA009. They stayed calm, evaluated the information that they had available, used the processes that they were familiar with and adapted to the situation.
JI: Lastly, still recalling the common way of attributing the role of heroes to the piloting crew of BA Flight 9, is there a little thing, like a daily habit or anything else, you always observed in Barry, that makes him absolutely human?
ATF: This is difficult to answer because you are asking if there is something that makes the hero seem human, but for me, the human that I
had known for 18 years became the hero – my hero. But, that wasn’t a different role, it was an additional role. After the event, he returned from his role as a Flight Engineer to his role as a father and husband and really he kept the two as different worlds. Maybe that is the answer to your question —he remained the same person that he always was. Also, he feels that he didn’t do anything particularly special—to him, he was just doing the job that he was trained to do.
Publishing
RF-MEMS Technology for High-Performance Passives (Second Edition)
5G applications and prospects for 6G
Jacopo Iannacci
Chapter 1
Introduction to MEMS and RF-MEMS: from the early days of microsystems to modern RF-MEMS passives
1.1 Introduction to semiconductor and microsystem technologies
Thinking of electronics and wondering about the intricacy of paths through which it has modified our habits, expectations and way of living in the last few decades, linking all these facts to the invention of the transistor (by John Bardeen, Walter Brattain and William Shockley at Bell Labs in 1947) seems quite spontaneous, both to people holding technical skills in semiconductor technologies, as well as to the general public. It is unequivocal that the transistor, as an elemental building block of any electronic circuit, was and is still today, the key element enabling the implementation of more complex and increasingly smart function/functionalities carried out by smaller, more integrated and less power-hungry devices.
Nonetheless, a quite critical consideration must be dragged into the spotlight before moving the discussion to the world of microsystems. In a rather effective attempt to reduce the complexity of a highly branched scenario, the transistor, according to a rather strict and classical definition, realises a limited set of main functions, as it can be exploited as a relay, i.e. an ON/OFF switch, as a varactor (i.e. variable capacitor), or as an amplifier, i.e. a device able to increase the amplitude of an electrical signal according to a certain proportionality law. None of these functions were enabled or invented by the transistor. The first electrically operated switch, or relay, is
attributed to the American scientist Joseph Henry in 1835. Its development was driven by the advancement of telegraph technologies. On the other hand, the first thermionic valve for amplification purposes was invented by John Ambrose Fleming in 1904. Bearing in mind this scenario, it is straightforward that transistors and, more generally, semiconductor technologies, have been playing a key role in the development of electronic devices for decades, with no leverage on the novelty or complexity of the function implemented by a single device, with respect to its vacuum valve traditional counterpart. The actual key-enabling feature of semiconductorbased components is miniaturisation, closely linked to the ease of integration. Just to provide a simple visual interpretation of the latter concept, it is sufficient recalling that the computational capacity of a modern smartphone, 55 or 60 years ago, would have required a mediumsize apartment full of thermionic valves, relays, wires and power cables, to be implemented. As a matter of fact, miniaturisation and integration enabled by semiconductor technologies, triggered a relentless trend in increasing the implemented complexity, counterbalanced by a moderate and, therefore, affordable spread in manufacturing and production costs, as well-framed by Moore’s law [1]. As a matter of completeness, the latter states that with the advancement of technology, the number of transistors that can be integrated in a square inch of silicon doubles roughly every two years.
On the other hand, the development of microsystem technologies has followed a path that exhibits several factors in common with semiconductors, yet marking fundamental differences from such technologies for many other critical aspects.
Microsystems, which are universally referred to with the MEMS acronym (Micro-ElectroMechanical Systems), are millimetre/submillimetre devices, realising a certain transduction function between two (or more) distinct physical domains, among which the mechanical one is always involved. More simply, regardless of the specific function it is conceived for, a MEMS device always features tiny structural parts that move, bend, stretch, deform and/or contact together. These peculiarities make microsystem devices particularly suitable for the realisation of a very wide variety of micro-sized sensors and actuators.
Provided with these basic concepts, a few considerations around the differences and similarities of MEMS versus semiconductor technologies can now be developed. Commencing from the most obvious diversities, while semiconductor devices are active, i.e. able to amplify an electrical signal, MEMS are exclusively passive, i.e. can just attenuate an electrical signal. However, transistors do not feature any movable or deformable part, i.e. they do not exploit the mechanical/structural domain to realise transduction functions.
From a technological point of view, MEMS and semiconductors share most of the same micro-fabrication steps, as will be discussed later in more detail. Both feature selective deposition/removal of conductive/insulating thin-films by means of lithography, despite a few peculiar steps and sequences of fabrication that are typical of MEMS only.
Both MEMS and semiconductors pursue the concept of miniaturisation. However, if semiconductor devices, beyond down-scaling, implement in the electrical/electronic domain the multi-physical function of traditional components, MEMS often miniaturise classical objects, keeping their transduction across physical domains. To this regard, the example of the aforementioned relay is quite explanatory. The traditional electrically operated switch exploits the transduction between the electrical and mechanical domain to realise the ON/OFF function. The transistor (when exploited as a switch) realises such a function entirely in the electrical/electronic domain. In contrast, a MEMS switch commutes between the ON/OFF state by coupling the mechanical and electrical domains, likewise the traditional device, despite the former being typically two or even three orders of magnitude smaller compared to the latter.
Also, importantly, the concept of miniaturisation is inflected in a radically diverse fashion when referring to semiconductor and MEMS devices. In the first case, as mentioned earlier, the trend in down-scaling has been continuous for decades. In order to build a more circumstanced idea, in Complementary Metal Oxide Semiconductor (CMOS) technology, the reference geometrical feature characterising the transistor is the channel length. In the mid-1980s such a length was around 4 μm, in the mid-1990s it was roughly 600 nm, in 2010 it reached 30 nm, while nowadays it is well below 20 nm [2]. This trend is, broadly speaking, addressed by the turn of
phrase ‘More Moore’, indicating the substantial hold of validity of Moore’s law.
The concept of miniaturisation played by microsystem technologies, is completely different with respect to the aforementioned sketched scenario. First, there is no such thing as a trend in evolving technologies and processes in order to make the same MEMS device smaller, from one year to the next. Instead, a strong driver exists in implementing more and more functionalities, possibly bringing them from the macro- to the micro-world. In other words, if the transistor was the same device over a number of decades, benefiting from being smaller and becoming, in turn, faster, less power consuming, more integrated and so on, the MEMS is a miniaturised object that benefits from implementing more and/or diverse sensing/actuating/transducing functions, by means of a device roughly of the same size. Because of these characteristics, microsystems, as well as other non-standard technologies not mentioned here for brevity, are generally labelled by the turn of phrase ‘More than Moore’ [3], indicating that their evolution through time does not follow Moore’s law, as they cannot be standardised according to a development trend exclusively built upon the continual shrinking of dimensions.
Eventually, from a different perspective, the concept of miniaturisation is radically dissimilar in quantitative terms, as well, when referring to semiconductors rather than microsystems. While CMOS transistors, as mentioned before, are framed today in the range of nanometres, a MEMS sensor/actuator can span from a few micrometres (in-plane dimensions), to hundreds of micrometres, or even to a few millimetres. Therefore, if a MEMS switch is nearly invisible to the naked eye when compared to a traditional relay, it is massive when placed beside a CMOS transistor.
In the following subsections, a few key considerations will be developed around the early days of MEMS, the most diffused microfabrication techniques and their market applications. Such concepts will help one to understand the core topic of this work, which will be introduced immediately after, i.e. MEMS for Radio Frequency applications, universally known as RF-MEMS.
1.1.1 The genesis of MEMS
As already discussed, the non-standard underlying peculiarity of microsystems with respect to semiconductors has emerged. Due to this reason, development of MEMS as a whole has not followed a wellestablished path, making it difficult to determine an exact point in time corresponding to the conception of microsystems.
From the point of view of technology, the key fabrication steps developed concomitant with the growth of semiconductor technologies starting in the 1950s. Nonetheless, the exploitation of such techniques aimed towards the manufacturing of microsystems commenced later, in the early 1970s. The advancement of silicon-based semiconductor technology motivated the scientific community to investigate, beside critical aspects related to the electrical/electronic characteristics, the mechanical properties of the materials involved in the manufacturing of semiconductors. In this regard, significant contributions can be found, for instance, in the valuable work of several authors concerning the mechanical properties of both bulk materials [4] and deposited thin-layers [5–7], dating from the mid-1950s to mid-1960s. Nevertheless, the exploitation of such techniques aimed towards the manufacturing of micro-devices with movable parts and membranes emerged later, in the period from the second half of the 1970s to the beginning of the 1980s.
Examples around how to exploit anisotropic etching to obtain a variety of 3D suspended structures from a silicon substrate are provided in [8]. Such techniques, together with those typically exploited for the fabrication of transistors and Integrated Circuits (ICs), led to the realisation of miniaturised pressure sensors [9], accelerometers [10, 11], switches [12, 13], and other devices for various applications, such as in the optical and biomedical fields. A remarkable article summarising the state-of-the-art microsystem technologies, and providing a comprehensive outlook around diverse applications, was authored by Petersen [14] at the beginning of the 1980s.
Nonetheless, it was with the further maturation of the surface micromachining fabrication technique [15] that the development of microsystems started to receive a significant boost, leading to the concepts of MEMS sensors and actuators as we know them today. A relevant contribution is represented by the work of Howe and Muller [16] in 1983, in which micro-cantilevers and double-supported beams were realised in
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regularly curved outline from north to south, looking like the segment of an immense circle.
The iron horns at the top are in place of bullocks’ horns usually placed on such memorials
About twenty miles to the east of our route, although perfectly hidden by the intervening rugged country and lines of forest-covered hills, is a very strongly defended Tanàla town called Ikòngo, a place which maintained its independence of Hova domination until the French conquest. With considerable difficulty and some personal risk, my friend, Mr G. A. Shaw, managed to gain
“BOUND BY BLOOD”
M S , B P
permission to visit this stronghold and introduce Christian teaching. The native chief, who became very friendly, wished to become closely allied to him by the custom of fàto-drà, or fàti-drà. This is a curious ceremony, in use among many Malagasy peoples, by which persons of different tribes or nationalities become bound to one another in the closest possible fashion. The name for it of fàto-drà i.e. “bound by blood”—denotes that its object is to make those entering into the covenant to become as brothers, devoted to each other’s welfare, and ready to make any sacrifice for the other, since they thus become of one blood.
The ceremony consists in taking a small quantity of blood from the breast or side of each contracting party; this is mixed with other ingredients, stirred up with a spear-point, and then a little of the strange mixture is swallowed by each of them. Imprecations are uttered against those who shall be guilty of violating the solemn engagement thus entered into. A few Europeans, who have overcome their natural disgust to the ceremonial, and to whom it has been a matter of great importance to keep on good terms with some powerful chief, have occasionally consented to make this covenant. Thus the celebrated French scientist, M. Alfred Grandidier, became a brother by blood with Zomèna, a chief of the south-western Tanòsy, in order to gain his good will and help in proceeding farther into the interior. But in his case the blood was not taken from the contracting parties, but from an ox sacrificed for the purpose; the ceremony is then called famaké. In this case, a pinch of salt, a little soot, a leaden ball, and a gold bead were put into the blood, which was mixed with water. Sometimes pulverised flint, earth and gunpowder are added to the mixture. In the case of Count Benyowski, who in 1770 was made king of a large tribe on the eastern coast, he and the principal chiefs sucked a little blood from each others’ breasts. The Hova formerly followed a similar custom, but with some variations; and so lately as 1897 a high French official made a somewhat similar covenant, with a principal chief in the extreme south of the island. The fàto-drà has doubtless been observed by the various tribes in all parts of Madagascar, but there appears to have been a good deal of difference in the details of the ceremonial attending it.
BÉTSILÉO HOUSES
We spent a day at Imàhazòny, the last Hova military post in this direction, before plunging into the unknown route across the forest to the coast. The people from the little vàla (homesteads) came running out to see us as we went by, most of them having never seen a white face before. We noticed how different the Bétsiléo dialect is from the Hova form of Malagasy; the n in the latter is always nasal (ng) in the former; while numerous words are shorter than their equivalents as spoken in Imèrina; and the consonantal changes are numerous. Besides this, the vocabulary is very different for many things and actions. About two hours’ ride on the following morning brought us to the large village of Ivàlokiànja. We went into a house, the best in the village, for our lunch; it was the largest there, but was not so large as our tent (eleven feet square), and the walls were not six feet high. The door was a small square aperture, one foot ten inches wide by two feet four inches high, and its threshold two feet nine inches from the ground; so that getting into most Bétsiléo houses is quite a gymnastic feat, and it is difficult to understand how people could put themselves to so much needless inconvenience. Close to it, at the end of the house, was another door, or window (it was difficult to say which, as they are all pretty much the same size!), and opposite were two small openings about a foot and a half square. The hearth was opposite the door, and the fixed bedstead was in what is the window corner (north-west) in Hova houses. In this house was the first example I had seen of decorative carving in Malagasy houses; the external faces of the main posts being carved with a simple but effective ornament of squares and diagonals. There was also other ornamentation, much resembling the English Union Jack. The gables were filled in with a neat plaited work of split bamboo. The majority of the houses in this and most of the Bétsiléo villages are only about ten or twelve feet long by eight or nine feet wide, and the walls from three to five feet high. Hereabouts, the doors seem generally to face the north or north-west, and the house runs nearly east and west. Hova houses of the old style, on the contrary, are always placed with their length running north and south, and their single door and window facing the west—that is, on the lee-side of the house.
T B M
AN UNPLEASANT RIDE
As Ambinàny, the Tanàla[28] chief, whose village we were bound for, did not make his appearance, we went off in the afternoon to another village, Iòlomàka, about three or four miles away to the south-east. It was a cold unpleasant ride in the drizzling rain. We reached the village, which is situated on a bare
hill, in an hour and a quarter, and with some difficulty found a tolerably level place on which to pitch the tent, but everything was wet. The rain came down faster than ever, and began to come through the canvas in some places. During the afternoon we in our tent formed for the villagers a free, and evidently popular, exhibition, which might have been entitled, “The Travelling Foreigners in their Tent.” We and our belongings, and our most trivial actions, were the subject of intensest interest to the people. They came peeping in and, uninvited, took their seats to gaze. I suspect they thought we travelled in a style of Oriental magnificence, for my companion’s gorgeous striped rug evidently struck them as being the ne plus ultra of earthly grandeur. But we did not look upon ourselves this evening quite in that light; for the slightly higher ground on two sides of the tent led the water into the structure, and there was soon a respectable-sized pool on my friend’s side of the tent, above which the boxes had to be raised by stones and tent-hammers; while the drip upon our beds raised the probability that we might be able to take our baths in the morning before getting up. It was our dampest experience hitherto of tent life.
The following evening found us at Ivòhitròsa, after one of the most difficult and fatiguing journeys we had ever taken in Madagascar. It was quite dark when we arrived here, wet, weary, muddy and hungry, having eaten no food since the morning.
But to begin at the beginning. Bed was so much the most comfortable place, with a wet tent, a small pond at one end of it, and a mass of mud at the other, that we did not turn out so early or so willingly as usual, especially as there was a thick mist and heavy drizzle, as there had been all night. The general public outside, however, evidently thought it high time the exhibition opened for a morning performance; and so, without our intending it, there was a performance, which, if there had been a daily paper at Iòlomàka, might have been described as consisting of five acts or scenes, as follows:—Scene first: Distinguished foreigners are seen lying in bed, so comfortably tucked up that they feel most unwilling to get out on to the wet and muddy floor. Curtains only half drawn (by an eager public) during this act. Scene second: Somewhat of a
misnomer, as D. F were, by the exercise of some ingenuity, not seen during the operations of bathing and washing. Scene third: D. F. seen by admiring public—who again admitted themselves—in the act of brushing their hair and performing their toilet. Scene fourth: D. F. seen at their breakfast; the variety of their food, dishes, plates, etc., a subject of mute amazement. Scene fifth and last: D. F. seen rapidly packing up all their property for their approaching departure. N.B.—Probably their last appearance on this stage. We packed up in the heavy drizzle, and fortunately, just as we were about to start, three or four Tanàla came up and agreed to be our guides. We had to wait until they had their rice, but at last we got away, soon after ten o’clock, rather too late as it turned out.
Our way for more than two hours was through the outskirts of the forest: a succession of low hills partially covered with wood, and divided from each other by swampy valleys. In these we had two or three times to cross deepish streams by bridges of a single round pole, a foot or two under water, a ticklish proceeding, which all our luggage bearers did not accomplish successfully. After crossing a stream by the primitive bridge of a tree which had fallen half over the water, we entered the real forest, our general direction being to the south-east.
And now for an hour and a half we had to pass through dense forest by a narrow footpath, where no filanjàna (palanquin) could be carried (at least with its owner seated on it). Up and down, down and up, stooping under fallen trees, or climbing over them, soon getting wet through with the dripping leaves on either hand, and the mud and water underfoot—we had little time to observe anything around us, lest a tree root or a slippery place should trip us up. At two-fifteen we came to an open clearing, and thought our difficulties were over, but presently we plunged into denser forest than ever, and up and down rougher paths. Notwithstanding the danger of looking about, it was impossible to avoid admiring the luxuriance of the vegetation. Many of the trees were enormously high, and so buttressed round their trunks that they were of great girth at the ground. The tree-ferns seemed especially large, with an unusual number of fronds; and the
creeper bamboo festooned the large trees with its delicate pinnate leaves.
A
DEEP GORGE
It soon became evident that we were descending, and that pretty rapidly. For a considerable distance we had a stream on our left hand, which roared and foamed over a succession of rapids, going to the south-east; and every now and then we caught glimpses of the opening in the woods made by the stream, presenting lovely bits of forest scenery in real tropical luxuriance. The sun shone out for a few minutes, but presently it clouded over, and heavy rain came on. The increasing roar of waters told of an unusually large fall, and in a few minutes we came down an opening where we could see the greater part of it, a large body of water rushing down a smooth slope of rock about a hundred feet deep, and at an angle of forty-five degrees. Three or four times we had to cross the stream, on rocks in and out of the water, with a powerful current sweeping around and over them. We found after a while that we had come down to the side of a deep gorge in the hills which rose hundreds of feet on each side of it, and down which the stream descended rapidly by a series of grand cascades to the lower and more open country which we could see at intervals through openings in the woods.
At half-past four we emerged from the forest and came down by a steep slippery path through bush and jungle. And now there opened before us one of the grandest scenes that can be imagined. The valley, down which we had come, opened out into a tremendous hollow or bay, three or four miles across, and more than twice as long, running into the higher level of the country from which we had descended. The hills, or, rather, edges of the upper plateau, rise steeply all round this great bay, covered with wood to their summits, which are from two thousand to three thousand feet above the lower country. Between these bold headlands we could count four or five waterfalls, two of them falling in a long riband of foam several hundred feet down perpendicular faces of rock. Between the opening points of this great valley, three or four miles apart, could be seen a comparatively level undulating country, with patches of wood and the windings of the river Màtitànana. On a green hill to the north side of
the valley was a group of houses, which we were glad to hear was Ivòhitròsa, our destination. This hill we found was seven hundred feet above the stream at its foot, but it looked small compared with the towering heights around it. At last we reached the bottom of the valley, crossed the stream, and presently commenced the steep ascent to the village. It was quite dark before we reached it, muddy, wet and tired out; we had been eight hours on the way, and five and a half on foot over extremely rough and fatiguing paths. The native chief and his people had overtaken us in the forest and went on first to prepare a house for us.
We found that the best dwelling in the village was ready, and a bright fire blazing on the hearth. It was with some difficulty that we got all our baggage arranged inside, for, although the largest house available, it was rather smaller than our tent, and nearly a quarter of it was occupied by the hearth and the space around it. At one side of the fire were sitting four young women, the daughters of the chief. A glance at these young ladies showed us that we had come into the territory of a tribe different from any we had yet seen. They were lightly clothed in a fine mat wrapped round their waists, but were highly ornamented on their heads, necks, and arms. A fillet of small white beads, an inch or so wide, was round their heads, fastened by a circular metal plate on their foreheads. From their necks hung several necklaces of long oval white beads and smaller red ones. On their wrists they had silver rings, and a sort of broad bracelet of small black, white, and red beads; and on every finger and on each thumb were rings of brass wire. In the glancing firelight they certainly made a striking picture of barbaric ornamentations; and notwithstanding their dark skins and numerous odd little tails of hair, some of them were comely enough. We had soon to ask them to retire in order to stow away our packages and get some tea ready. The house was raised a foot or so from the ground, the inside lined with mats, and so was a pleasant change from our damp lodgings of the previous evening.
A STRIKING PICTURE RICE-HOUSES
Next morning, on opening our window, we had before us, two or three miles across the great basin or valley, three waterfalls, one descending in a long white line and
almost lost in spray before it reaches the bottom. The sunlight revealed all the beauties of the scene around us, and made us long for the power to transfer to canvas or paper its chief outlines. Were such a neighbourhood as this in an accessible part of any European country, it would rapidly become famous for its scenery. We found the village of Ivòhitròsa to consist of twelve houses only, enclosed within a ròva of pointed stakes; but besides these are several ricehouses or tràno àmbo (“high houses”) mounted on posts five or six feet above the ground, each post having a circular wooden ring just under the flooring rafters, and projecting eight or nine inches, so as to prevent the rats ascending and helping themselves to rice. I sincerely wished last night that the dwelling-houses had a similar arrangement, for the rats had a most jovial night of it in our lodgings, being doubtless astonished at the number and variety of the packages just arrived. The house we are in, as well as others in the village, has carved horns at the gables, not the crossed straight timbers so called in Hova houses, but curved like bullocks’ horns. The people appear to have no slaves here, for the daughters of the chief, in all their ornaments, are pounding rice, four at one mortar.
At this part of the island the high interior plateau seems to descend by one great step to the coast plains, and not by two, as it does farther north; for our aneroid told us that we came down twenty-five hundred feet yesterday, and that the stream at the foot of this hill is only five hundred or six hundred feet above sea-level. And the two lines of forest one crosses farther on are here united into one.
The men and many of the women wear a rather high round skullcap made of fine plait; the women wear little except a mat sewn together at the ends, so as to form a kind of sack, and fastened by a cord round the waist, and only occasionally pulled up high enough to cover the bosom. Those who are nursing infants have also a small figured mat about eighteen inches square on their backs and suspended by a cord from the neck; this is called lòndo, and is used to protect the child from the sun or rain, as it lies in a fold of the mat above the girdle. Some of the men wear a mat as a làmba, and only a few have làmbas of coarse rofìa or hemp cloth. The people here
blacken their teeth with a root, which gives them an unpleasant appearance as they open their mouths; not all the teeth, however, are thus disfigured, but chiefly those at the back, leaving the front ones white; in some cases the lower teeth are alternately black and white.
The morning of one of our four days at Ivòhitròsa was employed in trying to get a good view of the largest of the waterfalls which pour down into the large valley already mentioned. Mounting a spur of the main hills, we had a good view of this chief fall up a deep gorge to the south, and so opening into the main valley as not to be visible from the village. This is certainly a most magnificent fall of water. The valley ends in a semicircular wall of rock crowned by forest, and over this pours at one leap the river Màtitànana. Knowing the heights of some of the neighbouring hills, we judged that the fall could not be less than from five hundred to six hundred feet in depth, and from the foot rises a continual cloud of spray, like smoke, with a roar which reverberates up the rocky sides of the valley; even from two or three miles’ distance, which was as near as we could get, it was a very grand sight.
MALAGASY RASPBERRIES
While on this little excursion we had a feast of another kind. On our way home we came across a large cluster of bushes full of wild raspberries. This fruit is common on the borders of the forest, but we never before saw it in such quantities, or of so large a size, or of so sweet a taste. The Malagasy raspberry is a beautiful scarlet fruit, larger than the European kind; and while perhaps not quite equal in flavour to those grown in England, is by no means to be despised; and we were able on that day to enjoy it to our heart’s content.
A G T G F D
During our stay at Ivòhitròsa we were surprised and delighted with the brightness and intelligence of many of the native boys. Although the dialectic differences of the Tanàla speech are many as compared with the Hova form of Malagasy, we obtained a large vocabulary from them as well as names of the forest birds and animals, and also those of trees and fruits. And as these forests and their vicinity are the home of several of the lemurs which have not yet been noticed in these pages, I will here give some particulars of four or five species.
The ring-tailed lemur (Lemur catta) is perhaps the best known of all the lemuridæ, from its handsomely marked tail, which is ringed with black and white bands, thus clearly distinguishing it from all the other species of the sub-order. And while almost every other lemur is arboreal, this species lives among the rocks, over which they can easily travel, but can be only followed with great difficulty. The palms
T G S C H
of their hands are long, smooth and leather-like, and so enable these animals to find a firm footing on the slippery wet rocks. The thumbs on the hinder hands are very much smaller than those of the forestinhabiting lemurs, as they do not need them for grasping the branches of trees. Their winter food is chiefly the fruit of the prickly pear; while in summer they subsist chiefly on wild figs and bananas. This species bears a sea voyage fairly well, so that they are often seen in Mauritius and Réunion, and even more distant places.
Another species of lemur, which inhabits the south-eastern forests, is the broad-nosed gentle lemur (Hapalemur simus). This animal is found among the bamboos, and it appears to subsist in a great measure on the young shoots of that plant. For biting and mincing up the stalks its teeth seem admirably adapted, as they are nearly all serrated cutting teeth, and are arranged so as mutually to intersect. It eats almost all the day long, and has a curious dislike of fruit. It is furnished with a remarkably broad pad on each of the hinder thumbs, so that it is able to grasp firmly even the smallest surfaces.
MOUSE-LEMURS
Perhaps the most beautiful and interesting—as well as the smallest—lemuriæ animals inhabiting Madagascar belong to the group called Cheirogale, or mouselemurs, of which there are seven species. As their name implies, they are very small, the dwarf species (Cheirogaleus minor) being only four inches long, with a tail of six inches. This pretty little animal is remarkable also for its large and very resplendent eyes, for the eye admits so much light at dusk that quite an unusual brilliancy is produced. The brown mouse-lemur ( Cheirogaleus major) is larger than the last-named species, being seven or eight inches long. Most, if not all, of the species live in the highest trees, and make a globular nest of twigs and leaves; they all appear to be nocturnal animals, as one might suppose from the structure of their eyes. The smallest, or dwarf, species, is said to be very shy and wild, very quarrelsome and fights very fiercely. Some of these little animals, if not all of them, have a time of summer sleep; and the tail, which is grossly fat at the beginning of that period, becomes excessively thin at its close, its fat being slowly absorbed to maintain vitality. The two (or three) species
of mouse-lemur here noticed inhabit the south-eastern forest region; others appear to be confined to the north-western woods.
[26] A writer in a defunct newspaper, The Madagascar Times, of 10th August 1889, describes in so true and graphic a fashion the old style of Malagasy filanjàna bearers, in the following rhymes, that I think they are well worth preserving in these pages:
Bearing their burdens cheerily, laughing the livelong day, Pacing o’er dale and mountain, wending their toilsome way; Puffing and panting, up hills steeply slanting, Skilfully bearing the filanjàna canting, Grumbling not at the sun’s scorching ray Wading through swamp and brooklet, splashing their course along, Bounding through plain and forest, thinking the track not long.
Chattering and pattering, with tongue ever clattering, Joyous if of it the Vazàha has a smattering; Growling not at the rain’s stinging thong Pacing with even footsteps, never losing time, Changing places racing, like the measured beat of rhyme Lifting and shifting, but never desisting, Always each other with pleasure assisting; Happy through all the toiling daytime.
Tramping with wondrous vigour, moving with easy grace,
Pausing not in their journey, dashing as in a race; Smiling and wiling, for a present beguiling, Ever joke-cracking, if the Vazàha is not riling
Such is the life of our native mpilànja, This is the marvellous way that they keep up the pace!
Note. “Vazàha” is the native word for Europeans; mpilànja means a filanjàna bearer.
ORNAMENTAL PATTERNS
[27] My friend, Mr G A Shaw, who was connected for several years with the Bétsiléo Mission, made a number of “rubbings” of this peculiar ornamentation. On exhibiting many of these at the Folk-lore Society, when I read a paper on this subject, one of the members expressed a strong opinion that these patterns must have had originally some religious signification; and another member remarked that the patterns closely resembled those on articles from the Nicobar Islands.
[28] The word “Tanàla,” which simply means “forest dwellers” (àla = forest), is a name loosely given to a number of tribes of the south-east, who inhabit the wooded regions and the adjacent
country. All, however, have their proper tribal names and divisions.
CHAPTER XIX
IVÒHITRÒSA
OUR Sunday at Ivòhitròsa was such a novel and interesting one that I shall depart for once from my rule of omitting in these chapters mention of our religious work. It was a wet morning, so that it was after eleven o’clock before the rain ceased and we could call the people together. A good many had come up from the country round on the previous day to see us, and we collected them on a long and pretty level piece of rock which forms one side of the little square around which the houses are built. When all had assembled, there must have been nearly three hundred present, including our own men, who grouped themselves near us. It was certainly the strangest congregation we had ever addressed, for the men had their weapons, while the women looked very heathenish. Some few had put some slight covering over the upper part of their bodies, but most were just as they ordinarily appeared, some with hair and necks dripping with castor oil, and with their conspicuous bead ornaments on head, neck, and arms. One could not but feel deeply moved to see these poor ignorant folks, the great majority of them joining for the first time in Christian worship, and hearing for the first time the news of salvation. And remembering our own ignorance of much of their language, the utter strangeness of the message we brought, and the darkness of their minds, we could not but feel how little we could in one brief service do to quicken their apprehension of things spiritual and eternal. We had some of our most hearty lively hymns and tunes, our men assisting us well in the singing; after Mr Street had spoken to the people from a part of the Sermon on the Mount, I also addressed them, trying in as simple a manner as was possible to tell them what we had come for, what that “glad tidings” was which we taught them. On account of the rain,
work in the afternoon had to be confined to what could be done in our tent, which was crammed full, and in our house.[29]
That there was great need for enlightenment may be seen from what we heard from the people themselves—viz. that there are (or were) eight unlucky days in every month, and that children born on those days were killed by their being held with their faces immersed in water in the winnowing-fan. So that on an average, more than a quarter of the children born were destroyed! The Tanàla names for the months are all different from those used in Imèrina; they have no names for the weekdays, and indeed no division of time by sevens, but the days throughout each month (lunar) are known by twelve names, some applied to two days and others to three days consecutively, and these day names are nearly all identical with the Hova names for the months. Each of the days throughout the month has its fàdy, or food which must not be eaten when travelling on that day
After our four days’ stay at Ivòhitròsa, we managed to get on our way towards the coast, not, however, without having considerable difficulty with our bearers, who were afraid of any new and hitherto untried route, for we were the first Europeans to travel in this direction. By tact and firmness we managed to secure our point; and on the Thursday afternoon we came down to the river Màtitànana, which is at this point a very fine broad stream, with a rapid and deep current. It flows here through a nearly straight valley for four or five miles in a southerly direction, with low bamboo-covered hills on either side, and its channel much broken by rocky islands. To cross this stream, about a hundred yards wide at this place, no canoes were available, but there was a bamboo raft called a zàhitra.
THE ZÀHITRA
Of all the rude, primitive and ramshackle contrivances ever invented for water carriage, commend me to a zàhitra. This one consisted of about thirty or forty pieces of bamboo, from ten to twelve feet long, lashed together by bands of some tough creeper or vàhy, which said bamboos were constantly slipping out of their places and needed trimming at every trip, and the fastenings had to be refixed. The zàhitra would take only two boxes and one man at a trip, besides the captain of the raft,
and when loaded was from a third to a half of it under water The civilisation of the people about here seemed to have not yet produced a paddle; a split bamboo supplied (very imperfectly) the place of one. Owing to the strong current and the feeble navigating appliances available, not more than about four trips over and back again could be made in an hour. And so there on the bank we sat from a little after two o’clock until nearly six, watching the ferrying over of our baggage, and then of our bearers. At sunset a good number of our men were still on the wrong side of the water, and so, as there was no possibility of getting them all over that day, and neither Mr S. nor I relished the prospect of a voyage on a zàhitra in the dark, we crossed at a little after sunset. We made a safe passage, but got considerably wet during its progress; Mr S. took an involuntary foot-bath, and I a sitz-bath. The rest of our men returned to a village overlooking the river, while we went a little way up the woods and, finding a level spot, pitched the tent there, our bearers who had crossed occupying two or three woodcutters’ huts which were fortunately close at hand.
A VILLAGE BELLE
During the three or four hours’ waiting on the river bank we had a good opportunity of observing the people from the village just above, who came down to watch our passage over the water. Amongst them was a girl whose appearance was so striking that I must attempt a description of her. She was a comely lassie, although a dark-skinned one, and was so ornamented as to be conspicuous among her companions even at some distance Round her head she had the same fillet of white beads with a metal plate in the front which we had observed at Ivòhitròsa, but from it depended a row of small beads like drops. On each side of her temples hung a long ornament of hair and beads reaching below her chin, several beads hung from her ears, and a number of white and oblong beads were worked into her hair at the back. Round her neck she had six strings of large beads, and another passing over one shoulder and under the arm. On each wrist were three or four silver bracelets, while on every finger and thumb were several coils of brass wire. Her clothing was a piece of bark cloth fastened just above the hips, over a skirt of fine mat, and on each toe was a brass ring. Thus “from top to toe” she was got up
regardless of expense; she was probably the daughter of the chief; anyhow, she was evidently the village belle, and seemed well aware of the fact.
T S
Note the wooden shields covered with bullock’s hide, and the charm on a man’s breast. They are very expert spearmen
Our route towards the sea was now over a comparatively level country, but not without many steep ascents and descents, and generally following the valley of the Màtitànana. As I took with me a
