Today's investment in and commitment to meaningful, commercially viable research will determine the shape and prosperity of tomorrow's microwave industry. Following its introduction in 2001 the second Microwave Journal guide to European research projects highlights the studies being undertaken by academic and commercial establishments to develop the innovations that will impact on the future of European and global technology.
Over the past 50 years, developments in microwave and high frequency engineering technology have made significant social, industrial and commercial impact. Global communications over microwave links, both terrestrial- and satellite-based, are commonplace. The boom in digital mobile communications saw new mass-market applications in the cell phone arena, Global Positioning Systems (GPS), satellite Digital Broadcast Services (DBS), etc., open up, and although the downturn in the telecommunications market has had a knock-on effect there is still significant development work being carried out.
A market that has survived a slump is the military sector, which is recovering well from cutbacks following the end of the Cold War. Here, the move towards electronic systems, with their associated size and weight reductions, has seen the microwave market benefit from system upgrades and modernization, and the development of new and increasingly complex systems.
Other areas which are advancing the exploitation of RF, microwave and millimeter-wave technology include intelligent transportation systems, RFIC tagging, radar, microwave heating, radio astronomy, and medical therapy and diagnostics. Work is also being undertaken to progress outwards in the frequency spectrum. There are moves downward to meet the upward shift in the traditional RF world and a push to make use of higher frequencies. For instance, a recognized new area of study is in the 0.1 to 10 THz range, where technologies for power generation, signal modulation and detection as well as system integration technologies have not been developed to any degree. Microwave techniques are also assuming increased importance in high speed digital electronics and optoelectronics.
Using the Guide
All of these sectors are developing through research and this supplement aims to highlight some of the current projects under investigation across Europe. It is intended as a representation of the depth and diversity of the research activity that is moving microwave technology forward and will play its part in shaping the future of the global microwave industry. The listing is by country within each section, and each entry has a short profile of current research studies. Contact information is also included to aid readers wanting further details.
As well as providing wide ranging geographical coverage the guide includes a diversity of work ranging from materials development, through broadband wireless systems, to military, satellite and space applications. In order to concentrate resources and expertise there is wide collaboration across academic and commercial institutes; therefore, complimentary commercial and independent test houses are highlighted, as are Pan-European projects.
Universities and Academic Institutes
Alphabetically ordered by country the following entries for each university name the main departments involved in microwave research, cover the extent of the work currently ongoing, outline the key areas of research, in some cases focus on a project of particular significance and provide contact details. To provide some continuity but also to introduce new work, the entries are a mixture of updates of academic departments featured in the 2001 supplement, where progressive and additional work is being undertaken, together with details of new research from universities not previously featured.
Technical University of Vienna
Research undertaken in association with Infineon Technologies in Munich, Germany.
Carrying on more than 12 years of cooperation, which began with a pilot project for a fully integrated direct conversion transceiver for a Digital Enhanced Cordless Telephone (DECT), the Institute of Communications and Radio Frequency Engineering, headed by Professor Arpad Scholtz, works in conjunction with Infineon Technologies, Corporate Research, under the direction of Werner Simburger. Concentrated in the field of RF circuits the joint initiative focuses on the design of high frequency circuits suitable for monolithic integration.
The main aim of the studies undertaken is to show that silicon and SiGe technologies are suitable for monolithic integration of high frequency circuits at frequencies approaching 100 GHz. This frequency regime used to be the domain of more expensive technologies like GaAs. The department develops circuits for analogue, digital and mixed applications, and although the work is in part devoted to basic research, it is primarily focused on developing future practical communications applications. Examples are wireless local area networks (WLAN) or point to multipoint systems.
Silicon and SiGe bipolar combine the potential to fulfil the technical specifications with the cost advantages, integration and manufacturing capabilities of standard silicon technologies. Due to Infineon's research potential circuits can be realized with state-of-the-art procedures. A new initiative focuses on the complementary metal-oxide semiconductor (CMOS) technology, especially for very high integration, and therefore circuits are being investigated on standard CMOS technologies.
Key Areas of Research
To illustrate the extent of the research undertaken, significant studies that have been or are ongoing will be highlighted, starting with the CMOS work referred to above. In this study a completely integrated 4:1 parallel-to-serial data multiplexer for high speed operation was realized in 0.12 mm CMOS. The circuit is composed from 2:1 multiplexer blocks. The multiplexer (MUX) works from DC up to 15 Gbps, which is the highest operating speed achieved by a 4:1 MUX in CMOS.
In another study a monolithic radio frequency power amplifier for 1.9 to 2.6 GHz has been realized in a 0.25 mm SiGe bipolar technology. The balanced two-stage push-pull power amplifier uses two on-chip transformers as input-balun and for interstage matching, and operates down to supply voltages as low as 1 V. A microstrip line balun acts as output matching network. At 1, 1.5 and 2 V supply voltages output powers of 20, 23.5 and 26 dBm are achieved at 2.45 GHz, with the respective power-added efficiency being 36, 49.5 and 53 percent.
In the field of oscillator development a 28 GHz monolithic quadrature voltage-controlled oscillator (QVCO) has been realized in a pre-production 0.4 μm SiGe bipolar technology with 85 GHz transit frequency. At 28.9 GHz, the circuit provides -14.7 dBm output power and phase noise of -84.2 dBc/Hz at 1 MHz offset. The two output signals are in quadrature with phase error of about 5°. Tuning of the QVCO may be done in the frequency range from 24.8 to 28.9 GHz, with nearly constant output power and the circuit consumes 25.8 mA from the 5 V voltage supply.
Other work concerns a 45 GHz SiGe active frequency quadrupler that claims to have the highest frequency based on reported silicon technologies. It represents a low cost and high performance alternative to common multipliers realized in GaAs and InP. It has a 3 dB bandwidth from 24 to 45 GHz and a maximum gain of +7.3 dB is achieved at 44 GHz.
Finally, a highly integrated 45 GHz phase-locked loop frequency synthesizer has also been realized. The monolithic circuit consists of a voltage-controlled oscillator with frequency doubler and divide-by-16 static frequency divider, and is manufactured in a pre-production 0.4 mm/85 GHz SiGe bipolar technology. The power consumption is 650 mW from the 5 V supply. External synthesizer building blocks are a commercially available PLL-IC, a passive loop filter and a reference oscillator.
Professor Arpad L. Scholtz, Technical University of Vienna, Institute of Communications and Radio Frequency Engineering, Gusshausstrasse 25/389, A-1040 Vienna, Austria; Werner Simburger, Infineon Technologies AG, Corporate Research, High Frequency Circuits, Otto-Hahn-Ring 6, D-81730 Munich, Germany.
Université catholique de Louvain, Louvain-la-Neuve
The Department of Electrical Engineering is one of the five departments of the Faculty of Applied Sciences that comprises four laboratories, including the Microwave Laboratory headed by Professor D. Vanhoenacker-Janvier. The laboratory is participating in the Research Center in Micro and Nanoscopic Materials and Electronic Devices (CeRMiN), and is a member of the Laboratoire Européen en Microélectronique et Microsystèmes with IEMN, Lille (France).
The Microwave Laboratory, established in 1966, began by global modelling passive and active waveguide structures, loaded with dielectric and magnetic materials. Two years later, the field of activity was extended to the evaluation of the impact of the troposphere on microwave communication systems. The late 1970s were marked by the increase of satellite communication systems, the launch of ESA test satellites and associated measurement campaigns in which the laboratory contributed. The rapid development of wireless-based systems in the 1990s led to a demand for mobile channel models, orienting the telecommunication activities. The collaboration with the university's Microelectronics Laboratory - a pioneer in silicon-on-insulator (SOI) technology - led to the extension of the microwave circuit activities to microwave SOI integrated circuits for low power, low voltage applications and included opto-microwaves. Around 1985, a third activity started, the investigation of the interaction between electromagnetic fields and the nervous system. Recently, this research has moved towards the analysis of biological effects of microwave fields and their social impact in the field of mobile phones.
Key Areas of Research
Microwave and RF communications, wireless communications and satellite communications are key areas of research in which the microwave laboratory has more than 30 years experience of tropospheric radio wave propagation, from an experimental, as well as a simulation and global modelling standpoint.
In the field of satellite communications, models for depolarization and attenuation due to rain, as well as for scintillation due to clouds, have been developed and tested against measured data. Over the last few years, two specific problems have been handled: the use of time series to check fade mitigation techniques (FMT) for given satellite scenarios and the use of existing propagation data for nongeostationary satellite constellations.
For wireless communications, an original physical-statistical model based on the uniform theory of diffraction has been developed and validated with experimental data, in cooperation with the CCSR of the University of Surrey. It has been shown to be particularly useful for high altitude platform systems (HAPS) and fixed broadband wireless access.
The research projects in multiple input multiple output (MIMO) communications cover MIMO channel modeling and antenna coupling, together with the development of space-time algorithms. A physical scattering model has been derived in collaboration with the Smart Antenna Research Group of Stanford University and is used to simulate the impact of various mechanisms on the performance of MIMO communication systems.
In its work on microwave and millimeter-wave electronics, the laboratory is experienced in the wideband modeling of passive planar elements in microstrip, coplanar and slotline topologies. The main activity however is devoted to design, modeling and characterization of passive and active elements integrated in SOI technology, especially fully and partially depleted SOI MOSFETs. This activity has been developed in cooperation with IEMN (Lille), CEA LETI, ST Microelectronics and the former Alcatel Microelectronics, as well as various European universities.
Research has also considered the analysis and characterization of electro-optical and opto-electrical transducers and the optical control of microwave devices. Also, accurate analysis methods have been investigated for the modeling of narrowband and wideband planar radiating devices, especially for the design of wideband Vivaldi antennas.
The research activity in bio-microwaves is currently focused on bio-electromagnetic effects due to GSM networks, thermal effects induced on the human head due to 900/1800 MHz mobile phone fields, as well as standard protocol and genotoxic effects. An extensive epidemiological study on rats has recently been started.
In accordance with Moore's Law, MOSFETs have been rapidly scaled to improve both the cost and performance of integrated circuits. From today's point of view, mainly due to the increase of short channel effects, conventional silicon MOSFETs have limitations for minimum feature sizes of about 35 nm. Therefore, the laboratory is developing and systematically analyzing the analog performance of alternative MOS device structures over a wide frequency band. These include fully depleted (FD) SOI MOS, dynamic threshold voltage MOS (DTMOS), graded channel MOS (GCMOS) and double gate MOS (DGMOS), in order to be able to overcome the standard MOS limitations and make an appropriate device selection in baseband and RF design. Characterization techniques and models for active and passive elements implemented in silicon technology have been developed for successfully designing microwave oscillators as well as low noise amplifiers at 2.4, 5.8 and 12 GHz.
Three new research projects are being developed; the first investigates the characterization and development of microelectromechanical systems (MEMS) for low power RF applications. The second considers the synthesis, design and modeling of magnetic nanowire implants for tuneable integrated and hybrid passive planar circuits. Here, the substrate used for the circuits consists of an array of magnetic metallic nanowires embedded in a polymeric membrane. Third, ballistic nanodevices are being analyzed.
Professor Danielle Vanhoenacker-Janvier, Department of Electrical Engineering, Université catholique de Louvain, Louvain-la-Neuve. E-mail: email@example.com; Web site: www.emic.ucl.ac.be.
Helsinki University of Technology
Professor Antti Räisänen heads the Department of Electrical and Communications Engineering where the Radio Laboratory and Signal Processing Laboratory have collaborated to form the Smart and Novel Radios (SMARAD) research unit. Key figures in this unit are Professors Pekka Eskelinen and Sergei Tretyakov from the Radio Laboratory, and Professors Visa Koivunen and Timo Laakso from the Signal Processing Laboratory.
SMARAD specializes in research into RF, microwave and millimeter-wave techniques and data communications signal processing. Areas of special interest include RF techniques for wireless data communications, radio channel modeling and measurement, new and smart materials and structures, smart (adaptive) antennas, receiver structures and architectures, and the signal processing algorithms they require. The results will impact particularly on future wireless communication systems. Significantly, the "Smart" of the research unit's acronym refers to adaptability of antennas or materials to RF signals or fields. To this end, in antenna measurement, work is being carried out on a novel method based on a radio hologram, which has already been successfully applied in testing the Odin satellite radio telescope.
Key Areas of Research
Three key topics will be highlighted here. First, under the auspices of Professor Räisänen is the study of radio holograms referred to above. Computer-generated holograms (diffractive elements) can be used for shaping millimeter-wave beams and for producing complex field configurations. The radio holograms being considered are of two distinct types, either amplitude or phase holograms. The former has been proven to be a feasible alternative as a focusing element in a compact antenna test range (CATR) in the mm-wavelength regime. Amplitude holograms have also been studied in other mm and sub-mm applications. In particular, the first experiments have been carried out in the mm-wave regime on the creation of nondiffracting radio wave Bessel beams, and on the creation of an electromagnetic vortex (a topological singularity that propagates with the electromagnetic field) in the radio wave field. The radio vortex could find applications, e.g., in direction finding and target ranging. New research on the design and fabrication of phase holograms for sub mm-wave applications has also commenced.
Professor Vainikainen is heading the study of antennas and radio wave propagation for mobile communications, particularly the antenna technologies required for future mobile radios. The research concentrates on developing small, multi-system, multi-element but low cost antennas that also have lowered radiation directed at the user of the mobile terminal. Another important area of antenna research is improved methods for characterizing the performance of the antennas, based both on laboratory measurements and the information on the propagation environments.
The propagation research deals with measurements of the multidimensional propagation channel and development of improved models of the radio propagation channel for system simulations. The latest models can be used to evaluate and design future adaptive antenna systems like MIMO antenna configurations that are expected to significantly increase the capacity of mobile radio systems.
Professor Tretyakov is investigating artificial composite layers and materials for use in radio engineering. As the artificial impedance surface near an antenna changes the distribution of the near field, less power is lost in the user's hand and head. The study optimizes the antenna so that the advantages of the artificial surface are most effectively utilized and new exotic composite materials (e.g., media with negative parameters) are being studied for microwave applications. Properties of waveguides containing exotic layers are studied. New wave solutions have been found: nondispersive waves, super-slow waves and periodical media with layers of "negative materials" are being considered. The possibility of designing a stop-band material with extremely wide stop bands has been found. Possible practical realizations of exotic materials are also being studied, as are metamaterials and layers with active and electrically controllable properties. Applications may be in wideband microwave absorbers and in antennas.
Professor Antti Räisänen, Helsinki University of Technology, Radio Laboratory, PO Box 3000, FIN-02015 HUT, Finland. Tel: +358 9 451 2241; e-mail: firstname.lastname@example.org.
University of Lille
The Institut d'Electronique, de Microélectronique et de Nanotechnologies (IEMN) - Institute for Electronics, Microelectronics and Nanotechnologies - is headed by Professor Alain Cappy. It was founded in 1992 and is the result of the fusion of three laboratories: the High Frequency and Semiconductors Center, the Laboratory of Optoacoustic Electronics, and the Laboratory of Studies on Surfaces and Interfaces. Forming the Department Hyperfrequences et Semiconducteurs (Devices and Microwave Department) under the direction of Professor Paul-Alain Rolland, the former is the largest, employing 160 permanent staff, and is where the majority of microwave research is carried out.
The key areas of research undertaken at IEMN include studies on modern electronics, innovative materials, microelectronics and nanoelectronics, microwaves, optoelectronics, electromagnetics, acoustics, ultrasound, microsystems, sensors and instrumentation. A key factor influencing the scope and effectiveness of the development work undertaken is that the department has at its disposal 1,500 m2 of clean rooms devoted to III-V micro and nanoelectronics (from epitaxial growth to characterization) and to silicon microsystems and microtechnologies. Key Areas of Research The research at IEMN is organized around seven scientific themes, all except one of which, acoustics, have microwave applications. The first of these concerns material and nanostructures where studies include both experimental intensive activities - molecular beam epitaxy (MBE), near field microscopy - and theoretical work, from highly prospective fields (frontier between semiconductors and biological molecules) to domains close to applications such as increasing frequency and power of microwave transistors. A significant achievement here concerns a study on the relaxation of strained epitaxial layers, which has led to state-of-the-art metamorphic InP type high electron mobility transistors (HEMT) grown on GaAs substrates.
One of the major areas of activity is the study of microelectonics and microwave devices, which covers four main areas: the physical simulation of III-V devices to optimize their technological fabrication; the realization of III-V devices for operation at millimeter-wave frequencies, which includes high gain, low noise and ultra fast digital circuits (heterostructures InAlAs/ InGaAs on InP or GaAs substrates) as well as power devices (GaInP/GaInAs power channel and GaN HEMT); silicon microelectronics devices, which encompasses the elaboration of electrical physio-chemical models to simulate the process and the electrical behavior of advanced CMOS and BiCMOS devices, and the study and realization of new CMOS architectures with Schottky source drain on SOI substrates; and quantum and terahertz devices, involving the design and fabrication of quantum wells nonlinear devices for the generation and transposition of sub-millimetric wavelength.
The main achievements of the work include: the realization and characterization of state-of-the-art metamorphic HEMT on GaAs with fts higher than 200 GHz for 100 nm gate length; the development of a 3D technology simulator for advanced components integrated on silicon; and the realization of a 290 GHz frequency tripler with 7 mW output power based on HBV diodes.
In the field of microtechnology and microsystems investigations are being carried out into MEMS for optical and microwave microsystems, on Si or III-V substrates, and microfluidics, with the latter being a new but growing area of activity.
Research into circuits and communication systems ranges from baseband signal processing to opto-milletric devices for local loop applications. The main challenges are to increase the frequency of operation by reducing the critical dimensions of active and passive components, and to develop new solutions for integration (mounting, interconnects, propagation structures and packaging).
Also being investigated are new telecommunication system architectures for local loop and ad-hoc networks to cover the last mile of the installation (interconnection of power lines, optical fibers, and 60 GHz radio channel for indoor and outdoor short-range high data rate applications). Significant achievements include: the design and realization of a two-stage 94 GHz InP low noise amplifier with 3.3 dB NF and 12 dB associated gain; an indoor fiber-radio link communication system at 60 GHz with a 155 Mbps data rate and lower than 10-5 raw BER; and a 1 V, 14 bit sigma-delta A/D converter using 035 CMOS technology.
Work in the optoelectronic and photonic circuits arena is mainly oriented towards optical communications and includes opto-millimetric device fabrication, optical switching, filtering and routing as well as optical modulation and photodetection up to 60 GHz. A new study concerning wavelength division multiplexing (WDM) is being carried out, based on add-drop multiplexers using photonic band gap (PBG) structures. Some significant results are the design and realization of a PBG add-drop multiplexer using a gallery mode resonator, a 1 x 4 "cascade" optical switch and a HBT-like three terminal edge-illuminated photo-detector (GaInAs/InP) with RF cut-off frequency greater than 60 GHz.
The wide topic of microwave sensors and instrumentation mainly concerns the biomedical domain, food industries, transportation systems, passive imaging and signal processing. An area of microwave activity concerns radiometric systems, where 3 GHz multiprobe systems for mammography and thermo-therapy controlled by radiometry, and 94 and 140 GHz real time passive imaging systems are under investigation.
Another area is non-destructive testing and specific instrumentation for signal processing.
Among the main achievements here is a fully integrated ultra fast space and time sampler (DC-10 GHz) with 60 dB dynamic range and six effective bits and a 94 GHz real time passive imaging system (limited to a linear focus plane array) using noise adding calibration and exhibiting a sensitivity better than 1 K.
Due to its size and wide range of research activities IEMN has numerous collaborations with academic and industrial laboratories, not only in France but also in the rest of Europe, USA, Japan and other Far East countries. Also, two common laboratories have been created with industrial societies. The first is in conjunction with Thales Research Technology and carries out work on GaN devices for high power microwave application. The second with RIBER studies large scale MBE epitaxial growth of phosphorous III-V materials.
The main objective is to focus on ultimate silicon and III-V devices and circuits (terahertz electronics), and on nanotechnologies for nano-optoelectronics, molecular electronics and biophysics.
Professor Paul-Alain Rolland, Département Hyperfréquences et Semiconducteurs, Institut d'Electronique et de Microélectronique du Nord. E-mail: Paul-Alain.Rolland@IEMN. univ-lille1.fr.
University of Erlangen-Nuremberg
The Lehrstuhl für Hochfrequenztechnik (LHFT) - Institute of High Frequency Technology - was founded in 1969 and was directed first by Hans H. Brand until he retired in 1998. Since then, Lorenz-Peter Schmidt has held the chair. Today, two additional university teachers extend the teaching staff: Siegfried Martius (Microwave Technology) and, within the framework of a guest professorship sponsored by Lucent Technologies, Bernhard Schmauβ (Optical Communication Systems).
Planar circuit theory, technology and experimental verification at microwave and millimeter-wave frequencies, with applications in advanced communication and radar systems, are the core fields of research. The institute recognized that in the frequency range between 0.1 and 10 THz, technologies for power generation, signal modulation and detection as well as system integration technologies have not been developed to any degree. Therefore, one of its major research activities is dedicated to THz sources, waveguides and receiver component technologies. This work started many years ago with fundamentals in the field of quasioptical technology, molecular gas filled ring lasers, optically pumped by CO2 lasers and sub-millimeter-wave frequency multipliers with varactor diodes.
In the field of laser technology and photonics, the main interests of research are in the development and optimization of laser beam sources and on laser-based measurement methods. Compact, RF-excited CO2 lasers are under development, which can be applied to industrial material processing as well as in specific measurement systems in the laboratory.
Research activities in the field of optical communication technology concentrate on ultra high capacity fiber optic transmission systems with channel bit rates up to 160 Gbps.
Key Areas of Research
Current research projects in the frequency range up to 150 GHz are dedicated to packaging and interconnect technologies for ultra broadband optical communication systems, including low temperature co-fired ceramic (LTCC) RF multilayer and novel substrate technologies development as well as multiport differential signal measurement technologies up to millimeter-wave frequencies. Further activities include microwave chip and module test methods, aimed at high volume, low cost in-production testing, and planar hybrid integrated circuits development, utilizing in-house thin-film and packaging technologies. Recently, a shielded anechoic chamber, equipped with a computer-controlled four-axis positioner for highly automated characterization of micro- and millimeter-wave antennas, has been installed and will be of help for ongoing work on antennas and sensors for short-range imaging, such as focal plane arrays.
At sub-millimeter-wave frequencies, the circuit design is based on planar as well as on metallic and dielectric waveguide technologies for the lower THz regime and utilizes quasioptical technologies at frequencies above. Dielectric lenses, ellipsoidal mirrors, wire gratings, serving as beam splitters or polarization filters and other components have been developed. These components are being used for experimental THz systems like radiometers and imaging transmission measurement systems.
For improved laser beam shaping and wavelength selection in RF-excited, sealed-off CO2 lasers, diffraction gratings with a novel structure are being developed and produced in the in-house electroplating facility. The examination of the gas compounds in such CO2 lasers is carried out by using a highly sensitive diode-laser spectrometer set-up, based on fiber optical components. Investigations on solid state and fiber lasers as well as nonlinear optical effects are further activities in this area.
In the field of optical communication systems the major fields of interest are modeling and simulation of OTDM system components, link design for ultra high capacity systems, fiber optical regeneration techniques and advanced modulation formats for high spectral efficiency wavelength division multiplexing in next generation ultra long haul systems. A high performance physical layer transmission system simulator is used to analyze the influence of component characteristics on system performance.
In research collaboration with groups from the University of Darmstadt and the University of Hamburg-Harburg, a vector 3D near field scanning system is being developed for 150, 300 and 450 GHz. This system will help to optimize the performance of novel quasi-optical oscillator and multiplier arrays within the project: Multi-Element Multi-Substrate Terahertz Integrated Circuits (MEMSTIC).
Recently, a quasioptical 2.5 THz radiometer has been developed, enabling simultaneous measurement of the O3, OH and H2 O concentration in the upper atmosphere. As a local oscillator, a methanol ring-laser at 2522.8 GHz is used, delivering up to 50 mW of output power. It is pumped by an RF-excited grating tunable sealed-off CO2 laser. Via a low loss, quasioptical diplexer the signal and the LO are fed to a mixer with recently developed substrate-less Schottky diodes, followed by a broadband, noise matched 6 to13 GHz IF amplifier.
In a DFG (German Research Foundation) sponsored research collaboration project, jointly conducted with a group from the University of Darmstadt, the application range of such Schottky mixer diodes is being extended to low noise operation at frequencies beyond 2.5 THz.
Professor Lorenz-Peter Schmidt, Lehrstuhl fŸr Hochfrequenztechnik, University of Erlangen-Nuremberg, Cauerstr. 9, D-91058 Erlangen, Germany. Tel: +49 9131 85 27215; fax: +49 9131 85 27212; e-mail: email@example.com.
Politecnico di Milano
Professor M. Santomauro heads the Dipartimento di Elettronica e Informazione, where the group of researchers involved in studies on microwave circuits is coordinated by Professor G. Macchiarella.
The main research work of the department is concerned with propagation of microwave and millimeter-waves, and with microwave circuits. For the latter, activity began many years ago with the development of CAD procedures for post-coupled waveguide filters, and for comb and interdigital filters in slab line. Now, most of the studies in the microwave circuit field (both active and passive) are devoted to mobile communications applications.
Key Areas of Research
The design, theoretical synthesis and computer-aided tuning of microwave filters are three strategic areas of activity. Taking each in turn, the aim of work to develop a space mapping technique for filter design is to derive suitable equivalent circuits for various classes of multiple-coupled-cavity filters whose parameters are assessed through electromagnetic simulations. These circuits are then used in the space mapping technique, allowing a strong reduction of the computational efforts in the numerical optimization of complex electromagnetic filter structure. Also, a design approach based on space mapping has been developed for designing comb filters with a large b/λ ratio and studies are currently under way to apply it to dielectric dual-mode filters.
As far as filter theory is concerned novel methodologies are being studied for the synthesis of equiripple Chebycheff filters with arbitrary placed transmission zeros (either complex or imaginary). Original procedures have been developed which, starting from the required filter mask, enable the determination of the coupling coefficient of an arbitrary filter topology, built up as a cascade of triplet and/or quadruplet sections.
In the field of computer aided tuning of microwave filters suitable strategies are being investigated for partial or complete tuning automation of generalized combline filters or duplexers. The procedures developed are based both on measurements of pre-tuned units and on equivalent circuits of the filters under alignment. In another study with obvious commercial applications various techniques are being investigated to improve the performances of linearized feed forward power amplifiers for last generation mobile systems.
A study commissioned by Forem, Italy, has yielded a general-purpose design program for multiple-coupled resonator filters with arbitrary placed transmission. The software is the result of studies performed over the last decade into filter synthesis and represents a very useful tool for designing high performance filters such as those used in mobile communications base stations. For a given set of electrical specifications, the program suggests some suitable topologies and computes the coupling coefficients, the external Q and the resonant frequencies of the resonators in the filters. These results can be used to fabricate various filter structures: generalized combline, dielectric single and dual-mode, etc.
Recently, the possibility of realizing asymmetric transmission zeros by coupling the input with the first two resonators (or the output with the last two) has been introduced, which can be employed to realize in-line filters with transmission zeros.
2001 saw the initiation of a research program investigating monolithic low phase noise oscillators using SiGe technology and supported by Ericsson Lab Italy. At present, studies are in progress concerning suitable design approaches for high Q monolithic inductors (both single and balanced).
Giuseppe Macchiarella, Dipartimento di Elettronica e Informazione, Politecnico di Milano, Piazza Leonardo Da Vinci n. 32, 20133 Milan, Italy. E-mail: Giuseppe.Macchiarella@ polimi.it.
Swiss Federal Institute of Technology, Zurich
In the microwave technology domain there are two research groups with complementary research interests within the Laboratory for Electromagnetic Fields and Microwave Electronics, which is part of the Department of Information Technology and Electrical Engineering (D-ITET). Professor Vahldieck heads the Electromagnetic Fields (EF) Group, whilst Professor Bächtold leads the Microwave Electronics (ME) Group.
Shared projects between both groups focus on photonic band gap structures and on highly integrated front-end design for 5 GHz channel sounders in MMIC and LTCC technology. Singularly, the EF Group examines computational electromagnetics in the area of CAD of passive microwave/millimeter-wave components, electromagnetic compatibility, integrated optics and nano-optics. Current projects are on field theory-based optimization techniques for microwave and millimeter-wave filters using a novel combination of rigorous field solvers and generic circuit prototypes, numerical analysis and optimization of reverberation chambers, numerical field analysis of optical MQW rib waveguide structures in travelling wave photodiodes and their integration with passive uniplanar microwave and millimeter-wave antennas, LTCC-based miniaturized antennas, photonic band gap structures for guiding and filtering electromagnetic waves at nanometer wavelengths, numerical analysis of plasmon resonances, together with the study of left-handed media.
The focus of the Microwave Electronics Group is on MMIC design and characterization, measurement techniques, millimeter-wave device and circuit technology, optoelectronics and integrated optics. Over the last decade the emphasis has been on device modeling and circuit design for wireless communication applications using GaAs MESFETs foundry technology.
Key Areas of Research
Taking the Electromagnetic Fields Group first, key initiatives include work on the EM-simulator-based optimization of passive filters, diplexers and active filters. The aim is to develop fast optimization techniques that use EM-simulators only to generate an accurate surrogate model of the filter structure while the actual optimization takes place in the parameter space of that model. In conjunction with a field-based sensitivity analysis, mapping between model parameters and geometry becomes very accurate. With this technique the number of field simulator runs can be reduced significantly.
The group's project on MQW rib waveguide structures and integration with uniplanar microwave circuits sets out to characterize transitions between photonic waveguide structures and coplanar transmission lines for highly integrated microwave/optical front-ends. Here the direct integration of a traveling wave photodiode with an active uniplanar antenna is being investigated.
An ongoing study of plasmon resonances works from the basis that certain colloidal particles like silver or gold can exhibit a resonant behavior at optical wavelengths. The extremely large electromagnetic fields associated with these plasmon resonances are of great importance for surface enhanced Raman scattering and in applications where nanoparticles are used as biological markers. Under investigation is the realistic situation of nonregular-shaped nanoparticles and what has been found is an extremely complex spectrum of resonances. Also under study is the possibility of utilizing plasmon resonances in light guiding structures and filters.
A PBG structures study recognizes that the interaction of two- and three-dimensional periodic structures is of growing importance in such diverse fields as antenna technology, microwave integrated circuits, and photonics and nano-structures. Here there is collaboration with the ME Group to investigate new PBG structures to guide and filter electromagnetic waves with the emphasis on numerical global modelling. This and the effect of defects can be used to optimize the behavior of PBG structures. In this project rigorous numerical methods to model electromagnetic fields are being developed and optimization techniques based on genetic algorithms are also applied.
The Microwave Electronics Group has developed a fully integrated RF front-end for a smart antenna Hyperlan receiver, with three antennas providing the electronics for superposition of the three RF signals with controllable amplitude and phase. Presently MMIC developments are under way with commercial GaAs-MESFET, GaAs-pHEMT, silicon CMOS and SiGe bipolar processes with projects on RF-transmitter/receivers in the 2.4, 5, 10 and 60 GHz ranges. Also under consideration are different linearization schemes for power amplifiers.
In an ongoing project extremely low noise cryogenic HEMT amplifiers are under development for applications in radio astronomy. A noise temperature of 5 K has been measured in a two-stage amplifier operated at an ambient temperature of 15 K. This is the lowest amplifier noise temperature achievable with any technology.
Studies in mm-wave device and circuit technology have seen an indium-phosphide-based HEMT process developed. Using commercially available epitaxial InGaAs/InAlAs layers the HEMT devices with 0.2 mm e-beam defined gates show typical transit frequencies of 150 GHz. Recently the gate formation processes have been further developed for 0.1 mm gate length. Suitable models for active and passive coplanar on-chip devices have been developed and MMICs have been designed and manufactured for wireless short distance communication in the frequency range up to 60 GHz.
Ongoing projects are modeling and characterization of mode-locked laser diodes, 980 nm pump lasers, vertical cavity surface emitting lasers (VCSEL) and dense integrated optical components for WDM applications. Of particular interest are optical interconnects in electronic systems between boards and modules. Novel concepts of optical waveguide structures with new functionalities are now under investigation. Here, densification in the time scale and in the length scale is the leading paradigm for future terahertz photonics devices.
Professor R. Vahldieck, Swiss Federal Institute of Technology, Zurich, Switzerland. E-mail: vahldieck@ifh. ee.ethz.ch.
Chaired by Bülent Özgüler, the Department of Electrical and Electronics Engineering has over 20 faculty members working in various areas of electrical engineering. Of these, Professor Abdullah Atalar (Provost and the former chairman of the department), Professor Ayhan Altintas, Associate Professor Levent Gürel and Assistant Professor Vakur B. Ertürk are involved in the field of electromagnetics, antennas and microwaves and form the Electromagnetics (EM) group.
For many years, the EM group has investigated both theoretical and computational electromagnetics, as well as electromagnetic compatibility (EMC). In the area of computational electromagnetics, the main focus has been on the modeling of complicated geometries on computers, modeling EM phenomena using circuit-theory concepts by employing parasitic extraction, AWE and SPICE, and the development of powerful software packages using fast solvers both in time and frequency domains such as finite difference time domain (FDTD), fast multipole method (FMM) and method of moments (MoM).
For antennas, the design and analysis of broadband antennas as well as the analysis and synthesis of arrays (printed and conformal) have been the main areas of activity, with considerable success. Radar cross section (RCS) computations (and measurements), stealth studies and ground penetrating radar (GPR) simulations have also been considered.
EMC investigations include the measurement of GSM base stations, radiation from PCB and chip geometries as well as radiation from and coupling through apertures on enclosures and shields, together with crosswalk and signal-integrity issues.
Another key area of research is spectrum management and propagation simulation for broadcasting, wireless and personal mobile communications, and other services. The spectrum management activities in the department were started in 1994 by the development of radio and TV frequency plans for Turkey. At present, the research is mainly focused on wireless service bands. Finally, integrated circuits, the simulation of very large circuits, and micromachined sensors and actuators are other research activities.
Key Areas of Research
In the field of mass wireless and mobile communications, the blossoming of new technologies and services necessitate the efficient, productive and versatile utilization of frequency spectrum. Today's high speed computers facilitate reliable and fast simulation of propagation phenomena and consequently the National Frequency Management System has been developed for the Turkish Government. It is composed of a database management and spectrum engineering system, which includes propagation simulation, link analysis, coordination and database integration, and other ancillary analyses.
For conformal antennas and arrays, the development of efficient and accurate analysis tools based on high frequency techniques are under study. In one part of this research, an analysis method based on a hybrid MoM/ Green's function technique in the space domain has been developed in order to analyze microstrip structures (various antennas and arrays as well as feeding structures, etc.) on electrically large, material coated cylinders.
Another area being considered is the RCS computations of targets, where fast electromagnetic solution algorithms are being developed. Real targets are large and have complicated shapes; therefore, curved surface modeling and meshing methods are utilized for FEM analysis. Also, fast electromagnetic solution algorithms, using MoM, FEM, single and multilevel FMM techniques, are being developed to solve these electrically large problems.
One of the projects is the development of design and analysis tools for conformal microstrip arrays and antennas. Although many practical applications have stringent aerodynamic constraints that require the antennas conform to the host body, the majority of the research on microstrip antennas focuses on planar structures. Therefore, efficient and accurate tools are required.
Using a hybrid MoM/Green's function technique in the space domain, different microstrip geometries on electrically large dielectric coated bodies have been investigated. This method is very efficient for electrically large arrays on material coated (large) bodies but its accuracy and efficiency depends on the high frequency asymptotic-based representations of the appropriate Green's function for dielectric coated cylinders. Two different Green's function representations that complement each other have been developed and used interchangeably, based on where they are valid and efficient for arbitrary source and field points.
An aim of this study is to develop a CAD tool to investigate large printed phased arrays on coated cylinders, with some of the future goals being to extend this method to multilayer cylindrical structures and develop a design and analysis tool that can treat arrays and antennas on arbitrarily convex coated bodies.
Projects under consideration include the development of fast and accurate design and analysis simulation tools for coupling, radiation and scattering of arbitrary and electrically large geometries using different techniques and combining different methods. Other possible fields of study are the design of novel antenna structures for broadband applications and the development of simulation tools for broadcasting, wireless and personal mobile communications.
Assistant Professor Vakur B. Ertürk, Bilkent University, Faculty of Engineering, TR-06533, Bilkent, Ankara, Turkey. Tel: +90 312 290 3154; e-mail: firstname.lastname@example.org; Associate Professor Levent Gürel: Tel: +90 312 290 2096; e-mail: lgurel@ee. bilkent.edu.tr; Professor Ayhan Altintas: Tel: +90 312 290 1489; e-mail: email@example.com.
Delft University of Technology
The International Research Center for Telecommunications-transmission and Radar (IRCTR) is allied to the Faculty of Information Technology and Systems (ITS). The director of the center is Professor L.P. Ligthart.
The IRCTR has been established to execute project driven research in several areas: antennas and propagation, radar and radar systems, remote sensing, wireless communications and mobile networks, and electronic systems for positioning and navigation. At the core of the center's work is internationalization, which manifests itself in scientific cooperation with recognized national and international research organizations and industries. To foster close relations with these partners an Industrial Advisory Board was established, tasked with guiding the direction of the research carried out. The general approach is to combine fundamental research with practical applications. For that reason the IRCTR research concept includes the realization of demonstrator systems, proving the value of research results.
Key Areas of Research
Consider the five areas of research outlined above starting with antennas and propagation. Here, the research focuses on the design, development and realization of smart, adaptive, reflector/array antenna systems and wideband wave propagation models. In the coming decade higher frequencies will be used for different radio and radar applications. For these millimeter-wave activities, IRCTR has outstanding indoor and outdoor measurement facilities, including an anechoic room and network and vector analyzers up to 110 GHz.
The research on radar and radar systems converges towards radar design techniques with emphasis on wideband radar and multi-parameter/ Doppler-polarimetric radar, radar networks, radar navigation, integrated radar communication and security systems. The research program of the remote sensing sector focuses on radar earth observation and on multi-sensor remote sensing of the atmosphere. The main motivation for this research is an increased general interest in and acknowledgement of the importance of the earth as a system.
Research on wireless communications addresses key issues in technologies, protocols and architectures for future systems, and networks supporting ubiquitous communications. The increase in wireless transmission capacity, number of mobile end systems, dynamicity in traffic profiles and heterogeneous networks necessitates fundamental studies validated with demonstrators, emulators and test beds.
Finally, for electronic systems for positioning and navigation, studies focus on the improvement of the performance parameters, accuracy, integrity, availability and continuity of service. There is a strong emphasis on participation in interdisciplinary and international programs on integration of communications, positioning and navigation. Instrumentation issues play an essential role.
Using its extensive experience on near field antenna measurements and its expertise in time domain measurements, the IRCTR carries out a full-scale research program on the development of a new generation of ground penetrating radar (GPR) systems. It includes the development of concepts for video impulse GPR and a stepped frequency continuous wave radar (SFCW radar), the development of improved GPR-antennas (including adaptive antennas), the development of a multi-sensor platform for precision high resolution subsurface imaging and the development of new methods of subsurface imaging based on interferometry and polarimetry.
The overall aim is to investigate new improved GPR technology, which will allow the creation of new GPR systems with challenging specifications. One of the promising application areas for GPR is humanitarian de-mining. Worldwide, enormous amounts of landmines are hidden in the ground. In TU Delft a multi-disciplinary research consortium has been set up to investigate solutions for this problem. In the context of a project funded by the Dutch National Technology Foundation (STW), a demonstrator for a humanitarian de-mining system making use of advanced GPR will be realized.
A second example is the IRCTR research on multi-static radar for automotive applications. During the past few years an X-band demonstrator containing five static antennas has been realized. Currently the project focuses on field experiments with real vehicles. In parallel with these experiments, new technology for higher frequencies is being investigated. Together with the universities of Achen and Birmingham research is being done on 35 and 70 GHz technologies for these applications.
Also, the Delft Program for Hybridized Instrumentation and Navigation Systems (DELPHINS) focuses on improving the pilot vehicle interface for navigation and guidance in order to increase safety in future air traffic environments. In the context of the project a compact display electronics unit for in-flight use is developed and integrated with the MIAS positioning system. The first flight tests were successfully performed resulting in the world's first demonstration of a GPS-based Tunnel-in-the-Sky Electronic Flight Instrument System (EFIS) display. At present, DELPHINS technology is being applied in the context of the NASA Aviation Safety Program, the Boeing 737-900 Technology demonstrator and the King-Air laboratory aircraft of Ohio University.
The center is well known for building the Doppler-polarimetric research radars DARR and TARA. One of the challenging activities for the coming years will be operationalization of CESAR, the Cabauw Experimental Site for Atmospheric Remote Sensing. In the context of this multi-disciplinary initiative an ambitious test site for atmospheric research will be realized at the premises of the Dutch National Meteorological Institute (KNMI) at Cabauw (near to Lopik, the Netherlands). The Transportable Radar System (TARA) will play a central role in this research initiative.
In the area of wireless communications a number of projects are carried out with leading industries and providers. Current research focuses on transmission schemes like OFDM, WCDMA and transmission techniques like space-time coding (including research on smart antennas). The realization of a third generation tested is proposed. In the near future projects on personal area networks will be started.
Professor L.P. Ligthart, director of IRCTR or A.C. de Ridder, controller of the IRCTR. Tel: (+31) 15 278 1034, fax: (+31) 15 278 4046; Web site: www.irctr.tudelft.nl.
The Wireless Communications Research Group (WCRG) in the Department of Electronic and Electrical Engineering conducts the microwave-engineering research under Professor Vardaxoglou. This group also includes the Center for Mobile Communications Research (CMCR), which is the department's flagship research center.
Focused on antenna and wireless systems, the research interests include applications in mobile and satellite communication systems, microwave and mm-wave engineering. Much of the activity builds on a foundation of expertise in the area of resonant and periodic structures, exploited as frequency selective surfaces (FSS), in addition to metamaterials such as electromagnetic band gap (EBG) and double negative (DNG) structures. Responding to the needs of industry, the CMCR was established in 1998 to exploit this strong research caliber in the design of antennas and associated components for mobile applications.
The work has focused on the miniaturization of antennas, with emphasis on preserving their in-use efficiency through isolation from the application, low user-proximity influences on the products and a significant reduction to the specific absorption rate (SAR) in the user.
Key Areas of Research
Projects currently running include low SAR antenna research and design for mobile handsets, 3G communications antennas, optically activated microwave circuits and antennas, frequency selective surfaces, metamaterials, electromagnetic and photonic band gap structures, arrays and FSS for mm-wave applications, local multipoint distribution system (LMDS) flat plate antennas, multichip interconnects and RF systems.
As technologies are integrated to multi-function applications, antennas have to perform a wide range of tasks to meet the pan-world demand on personal telephony and mobility. Against this background the CMCR has forged considerable expertise in the analysis and design of such systems. Using a (32x) computer cluster, the department has the capability of undertaking simulations with the degree of sophistication that is required to meet the stringent design demands. The design prototypes are produced using the latest in photolithographic imaging, etching, laser and microwave measuring technologies. This includes the full 3D pattern characterization and efficiency assessment of handsets.
Owing to health precautions, the SAR safety requirements are now widespread and mobile phone handsets will have to produce lower exposure levels. Developing expertise gathered from the Global Positioning System antenna product, prototype antennas for cellular telephones have been created to reduce emissions into the body by as much as 85 percent.
The breakthrough occurred using a combination of the benefits of the PC cluster and innovative laser technologies used in the manufacturing processes. This puts the university in an excellent position to be the leaders as low SAR solution providers in the UK for the telecom industry.
Similar patented technology products are now being designed specifically for Bluetooth, Personal Communications Network (PCN) and Universal Mobile Telecommunications System (UMTS). These antennas reduce the need for filters (thus lowering component costs) and for a large ground plane (low handset interaction). They can be embedded into the handset using a balun to isolate electrical noise, which increases the reliability and signal strength of short-range devices, such as Bluetooth.
The work by the WCRG has been funded by the UK Engineering and Physical Sciences Research Council (EPSRC), in addition to companies such as Sarantel, GEC, British Aerospace, Orange and regional small to medium enterprises (SMEs). The group also has major collaborative programs with the Queen's University of Belfast, Northern Ireland, the Politechnico di Torino, Italy, and the University of Patras, Greece.
Professor Vardaxoglou, Wireless Communications Research Group, Department of Electronic and Electrical Engineering, Loughborough University, Loughborough, Leicestershire, LE11 3TU, United Kingdom. E-mail: J.C.Vardaxoglou@lboro.ac.uk; Web site: www.lboro.ac.uk/departments/el/ (publications list).
Queen's University of Belfast
The High Frequency Electronics Research Group is headed by Professor Vincent Fusco and its activities include RF, microwave, millimeter-wave packaging, nonlinear circuits, and active and passive antenna technologies, as well as low loss THz filters.
The physical resources available to the group are of the highest industrial standard. Facilities include soft/hardboard production and thermally controlled small/large signal V-band monolithic microwave integrated circuit (MMIC) probing. Anechoic chamber facilities are also available, and the group also has a full suite of Agilent's ADS linear and nonlinear design software together with Ansoft's HFSS, Microstrips, Sonnet and Momentum electromagnetic simulators. The group has its own networked CAD facility comprising 20 UNIX and PC workstations. There is access to a fully equipped machine shop with two CNC lathes for production of mechanical enclosures and two wire bonding machines for use with microwave devices, with a research engineer and a research technician providing technical support.
Belfast is a major UK center for the design and application of MMICs as well as active and passive antennas. Consequently, the group has expertise and technical skills that are focused on the creation of novel front-end solutions with added functionality and reduced complexity for a variety of applications. Research programs are designed to produce synthesis and analysis tools, and experimental demonstrators for these novel wireless front-ends. These circuits are elements for insertion in low cost products for commercial and consumer applications such as WLAN and low cost phased array radars. Work programs combine advanced nonlinear device and EM circuit simulation, analytical methods and experimental practice, in order to realize MMIC, MIC and antenna circuitry.
Current projects are sponsored by the Engineering and Physical Sciences Research Council (ESPRC), the EU, via the N. Ireland Industrial Research and Technology Unit (IRTU), and by industry. The QUB group has a number of well-established links with UK and international industry including OMMIC, AVX-Kyocera, M/A-COM and TDK, which has an industrial implant on site at the QUB HF laboratories.
Key Areas of Research
Examples of typical projects include smart structures for mm-wave front-ends and integrated self-tracking antennas. In the former project, the group created the first reported complete self-tracking, mm-wave, 60 GHz dual-channel transceiver, based on nonlinear analogue phase synthesis techniques. Advanced fabrication technologies were also examined for low cost mixed technology MMIC multi-chip carrier realization. The second project investigated the theoretical and practical basis for the realization of all silicon antennas and integrated homodyne receivers operating at 60 GHz.
Also, research on active and passive antennas for portable radio systems has shown the advantages as well as the limitations of electromagnetic simulators. Consequently, new EM theory applicable to these structures and measurement techniques are being investigated. This work has yielded a number of novel structures for mobile and base station antennas, some of which have been patented.
In the area of microwave and millimeter-wave mixer design new techniques have been developed for the creation of phase conjugate mixers for use in self-tracking antenna applications. This, together with the department's work on micro-machining and integrated antenna realization, has lead to all silicon self-steered receivers and ultra low loss silicon interconnects for use at millimeter-wave frequencies.
Recently the QUB High Frequency Research Group has been leading work on the creation of ultra low loss frequency selective surfaces using advanced micro-machining techniques for space borne applications. This work is being carried out in collaboration with Astrium, Rutherford Appleton Laboratories, the N. Ireland Semiconductor Research Center and Loughbrough University. Work on advanced electronic packaging techniques including electromagnetic/ thermal modeling of flip chip MMIC devices is also being carried out.
Other ongoing work represents a major extension to the concepts currently used in the development of low cost beam steered reflect arrays, since it includes the possibility of pattern control and direct signal modulation, using a totally integrated silicon solution that is compatible with standard processing technology. Beam formation and other control functions are executed under DC control of diode properties, and no additional RF components such as conventional phase shifters are required. Consequently, a broad variety of applications become available, such as self-steered sensors, electronically controlled beam-steered antenna for broadband mobile communications applications for imaging sensor, active RCS control, and direct DC to microwave signal phase encoding.
The key techniques being developed here are spatial phase shifters that exhibit low reflection loss. To concurrently achieve this and polarization agility the group is developing a new class of low series resistance silicon diodes based on a novel silicon-on-insulator (SOI) technology. Waveguide simulation techniques are being extensively deployed to investigate infinite array behavior. Finite array behavior, as well as electromagnetic codes, is also being developed so that demonstrator behavior can be accurately assessed.
Professor Vincent Fusco, High Frequency Research Laboratories, Queen's University of Belfast, Ashby Building, Stranmillis Rd, Belfast BT9 5AH, Northern Ireland: Tel: +44 28 9034 2076; fax: +44 20 9066 7023; e-mail: firstname.lastname@example.org; Web site: www.qub.ac.uk/hfeg.
One area that has witnessed a lot of change is the commercial and independent research field, with the slump in the telecom market having significant impact. Commercial reality has also hit home with the move towards less Government funding putting the pressure on to get industrial backing and support. Against this background, commercial confidentiality and competitive sensitivity often limit what companies are willing to divulge. Therefore, Microwave Journal is grateful to those who have contributed.
National Physical Laboratory
RF and Microwave Research Team, NPL, Teddington, UK.
The research carried out by the team is undertaken to push existing microwave technology to its limits to develop the most accurate measurements and instrumentation. This research underpins electrical measurements carried out within UK industry and the National Measurement System Policy Unit (NMSPU) of the Department of Trade and Industry (DTI), which funds the work to ensure that UK industry can have confidence in the measurements it performs on an international scale.
Studies focus on microwave measurement standards in transmission media such as hollow waveguides, coaxial lines, dielectric waveguides and planar lines in high frequency integrated circuits. The four main measurement parameters - power, attenuation, impedance and noise - are highly interdependent, and progress in the development of measurement standards in this field requires a predominantly integrated approach. The main application areas for guided wave standards are those served by the following industries: telecommunications, aerospace, defense, radar, EMC, and health and safety.
As NPL develops new solutions to overcome the challenges of realizing the most accurate measurement standards, it forges new techniques and technology that can be applied to the development of new microwave measurement and test instrumentation for all these industrial sectors. Technical advances in these areas are dependant on new applications of technology and the "stretching" of existing technologies to develop new capabilities. Significant impetus behind the need for new technologies is the drive to increase the functionality, complexity and speed of electronic circuits. This requires electrical quantities to be measured at higher frequencies and with greater accuracy than ever before.
Key Areas of Research
NPL is focusing on developing innovative approaches to the realization of national standards for microwave measurements in power, attenuation, impedance and noise. Much of this research is focused on developing new measurement capabilities in response to industrial requirements. For example, it is extending its existing traceable power measurement capabilities to allow the measurement of peak power for wireless communications. It is also investigating new mechanisms for disseminating accurate traceable measurements across the country by providing remote calibrations via the Internet.
The National Physical Laboratory also has a comprehensive EMC and dielectric materials measurement research capability. Research is carried out on a range of EMC measurement techniques. In particular, investigations of more cost-effective measurement methods using fully anechoic rooms, GTEM and EUROTEM cells, and reverberation chambers are being carried out to refine these methods and ensure that they are technically viable. In the field of dielectric materials measurement, NPL carries out research to evaluate new, more cost- effective measurement techniques. Currently, research is underway to evaluate techniques for measuring properties of thin films from RF to millimeter-wave frequencies, to study the metrology of structured, active and "smart" composite materials, and to improve the accuracy of dielectric resonator measurements for higher permittivity, lower loss materials.
There are two directions being followed for the development of microwave measurement capabilities: improvements and extensions to existing standards to support the more demanding use of existing technologies and frequencies, particularly for mobile communications; and the development of standards up to and beyond 100 GHz. In addition, as many users are seeking calibration over a continuous range of frequencies rather than at "spot" frequencies, that capability is also being developed. Techniques are also being developed for making measurements of passive intermodulation (PIM) products.
With some guided wave standards being barely in advance of industrial requirements, there is a need to re-examine the technical basis upon which current standards are realized with the objective of identifying technologies and techniques, which could result in step improvements in the primary standards. NPL is also working with a range of instrumentation manufacturers to integrate the developments in measurement technology into new products and systems. The transfer of technology from the Government research at NPL to UK and worldwide industry is a high priority.
A particular project investigated the measurement of overhead power lines using a new non-contact electro-optic sensor. The research required the modification of an existing sensor, in which NPL was in the development, for a new sensor application and the characterization of its performance in experimental trials. The voltage and current signature recorded in trials matched that expected by the customer indicating that this new sensor could be applied to this new application. NPL is currently performing a project to investigate the provision of measurement standards to support the mobile and satellite communications markets, specifically for measurements of PIM and antenna noise.
Part of the Mobile Telecommunications and Health Research Program is a project to provide traceable calibrations to microwave parameters in support of dosimetry studies into the physiological effects of electric and magnetic fields emitted by commercial GSM mobile phones and Terrestrial Enhanced Trunked Radio (TETRA) devices.
Projects are proposed to investigate the existing standards base on the existing RF and microwave standards of all principal quantities of power, attenuation, impedance and noise, review the status and limitations of these artifacts and/or systems, and propose new or novel means by which a future generation of standards with lower uncertainties might be achieved.
Malvern Technology Park, St. Andrew's Road, Malvern, UK.
Microwave Circuit Design and Prototyping Group.
The group has considerable experience in the design of hybrid MIC and MMIC-based sub-systems covering the 1 to 100 GHz frequency range. Contract design work is undertaken for both commercial and military applications and covers a diverse range of markets. Recent projects for major blue-chip customers include a 2 to 18 GHz high dynamic range receiver for an electronic surveillance system, a 1 W, Ka-band, power amplifier for a fixed wireless telecommunications link and a 94 GHz receiver, using indium phosphide MMIC technology, for a cloud profiling radar.
The Microwave Circuit Design and Prototyping group is actively involved in developing state-of-the-art MMIC components and low cost assembly techniques for realizing ultra broadband mm-wave receivers. These subsystems are used in QinetiQ's patented mm-wave security scanner systems that are supposedly set to revolutionize security monitoring in public places. Critical to achieving low cost is the use of highly integrated, single chip, mm-wave receiver front-ends and flip-chip assembly methods.
Key Areas of Research
The design team has access to a state-of-the-art computer aided design suite and a dedicated measurement facility allowing device modeling and circuit characterization up to 110 GHz. A key differentiator in the group's capabilities is the custom model database that it has assembled from accessing numerous GaAs foundries worldwide. This is a significant benefit to customers wishing to develop a custom MMIC design as it has allowed the design team to build up a portfolio of "right first time design" success.
Complimenting the design team is a state-of-the-art prototyping facility. The facility offers a unique rapid prototyping service claimed to be unsurpassed for responsiveness in Europe, allowing customers to develop working prototypes in weeks rather than months. Low volume manufacturing of advanced microwave and mm-wave modules covering the 5 to 100 GHz frequency range is available internally. Alternatively, for customers requiring higher volume quantities, or mass production, then QinetiQ can provide bespoke design solutions with outsourcing of volume assembly and test through its established network of suppliers.
Consequently, the following services are offered: custom MIC/MMIC design and characterization to 110 GHz; microwave and mm-wave module development from small quantities to thousands; flip-chip die attachment to 5 mm placement accuracy; hybrid assembly (including wire/tape bonding, vacuum re-flow soldering, resistance/DC welding and hermetic testing); and environmental testing.
Steve Ashley, Business Group Manager (Microwave Sensors), Malvern, UK. E-mail: saashley@QinetiQ.com.
One of the main reasons for the formation of the European Union was to foster and encourage cross-border cooperation and one area where this has been successful is in the research field. Testimony to this are the projects featured, where an area in need of study has been identified and the leading exponents in the field assembled, with clear goals and objectives.
CANVAD - Carbon Nanotubes for Microwave Vacuum Devices
The aim is to demonstrate that CNT-based cold cathodes can satisfy the future telecommunications requirement for high frequency (30 to 100 GHz) compact and low cost microwave amplifiers. Its objective is to achieve an emission current density of 1 A/cm2 modulated at 30 GHz from a CNT-based cold cathode. The cold cathode will consist of an array of CNTs with an integral extraction grid positioned 5 to 10 μm from the CNT emitters.
Intermediate goals are the fabrication of arrays of identical and vertically aligned CNTs, and the design/fabrication of low capacitance CNT-based field emission cathodes. The study will aim to verify that 1A/cm2 of emission current can be obtained in DC mode from the cathodes, and using a RF modulated input, validate that the device delivers 30 GHz modulated current at a density of 1A/cm2 .
This project is divided into seven work packages. The first, nanolithographically defined growth of aligned nanotubes aims to produce arrays of identical and vertically-aligned CNTs. This will be achieved by using a three-pronged approach - precise control of the size and the position of the catalyst dot by nanolithography, selection of a high temperature diffusion barrier for high yield and uniformity, and optimization of growth parameters to obtain selective growth of nanotubes.
The objective of the second is to fabricate a cathode that integrates the array of CNTs with an extraction grid positioned 5 to 10 μm away from the array. This includes the design of a low capacitance and high transparency extraction grid, and the determination of a suitable technology to integrate the CNTs with the grid to form the compact cathode.
The third work package relates to the emission properties of the cathodes, from which will be determined the emission current density (~1 A/cm2 ), emission uniformity, energy distribution of the emitted electrons, and stability/lifetime of the cathodes. Following on, the fourth provides the simulations and modeling support for the preliminary design of the microwave vacuum amplifier. An experimental test system will also be set up to measure the emission current density modulated at 30 GHz.
Work packages five and six will cover assessment and evaluation and dissemination and implementation, respectively, while seven will ensure that the project will be executed in the most effective fashion and the results are fully exploited technologically and commercially.
The progress of the project will be measured using the main deliverables: nanolithographically defined growth of aligned CNTs, design and fabrication of CNT-based cathode with a capacitance of 2 to 3 pF/mm2 , and cathodes delivering 1 A/cm2 emission current densities modulated at 30 GHz.
The project started on the 1st of April 2002 and is due for completion on 31st March 2005. Being at such an early stage there are, as yet, no new results concerning microwave vacuum devices. However, first results concerning the nanolithography-localized growth of aligned nanotubes and the fabrication and electrical characteristics of carbon nanotube-based microcathodes have been published.
The prime contractor is Pierre Legagneux, Thales Research & Technology, Orsay, France. E-mail: Pierre.email@example.com. Project partners: Thales Electron Devices, France; Cambridge University, UK; Fribourg University, Switzerland; and the University of Groningen, the Netherlands.
IMPACT - Integration of Microwave Performance into Advanced CMOS Technology
The project aims to push CMOS technology for products operating well into the microwave radio frequencies (5 to 20 GHz), which will be achieved by fabricating demonstrator devices and circuits in advanced 100 nm CMOS process technology. The aim is the realization of an early knowledge and the basis of development for future high frequency CMOS applications.
Therefore the key technical and scientific objectives of IMPACT include the following: to evaluate the added value of CMOS technology for microwave circuits in the 5 to 20 GHz frequency range; to develop and implement analogue compact models for active and passive components for frequencies up to 50 GHz; and to develop and integrate active and passive devices suited for high frequency applications in advanced CMOS technology.
First, design work is needed to define demonstrator devices and circuits that represent the application domain of microwave CMOS technology. In order for this design activity to be sufficiently accurate and predictive, compact models need to be developed that properly describe the high frequency behavior of all circuit elements. Then, active and passive devices need to be defined and integrated, not only to electrically test the validity and accuracy of the compact models, but also to fabricate the demonstrator circuits.
To carry this out three technical work packages have been defined: circuit design, modeling and process optimization. Initially, existing 100 nm front-end CMOS technology will be used to obtain model parameters for active devices. Similarly, a first model description of passive devices will be derived from earlier integration and modeling experience. Using this information, and in successive iterative loops, the CMOS technology will be optimized using the input obtained from the design and modeling groups.
At the end of IMPACT, an optimized CMOS technology for microwave frequency operation will be available together with improved models for active and passive devices, and optimized design methodologies for microwave circuits and systems.
The early availability of MOS transistors fabricated within the IST-HUNT project has made it possible to carry out a detailed characterization and modeling of the 100 nm CMOS technology as one of the first activities within the study. Both MOS Model 11 (MM11) and Chalmers parameter sets have been made available to the consortium for circuit design and technology optimization. Currently, NMOS transistors with cut-off frequency in excess of 120 GHz and maximum operating frequencies above 80 GHz are available. It is expected that layout and technological optimizations will bring maximum operating frequencies well above 140 GHz.
The work on transistor optimization is being carried out in parallel with the development of RF passives in an advanced copper/oxide back-end of line, with the possibility of fabricating inductors either in the top levels of metallization or in a post-processed way using BCB and copper. Models based on initial experiments and on electromagnetic simulations have been provided to circuit designers.
A mask set specifically designed for IMPACT is currently being finalized. It contains an extensive set of RF front-end circuits (LNAs, VCOs, etc.) designed to operate at frequencies ranging from 5 to 40 GHz. Some of the circuits include electrostatic discharge (ESD) protection schemes designed to be effective at very high operating frequencies without compromising circuit performance. This mask set also contains a broad range of technology characterization vehicles which, combined with the results obtained from the circuits, will allow for further circuit and technological optimization in the second learning cycle foreseen within the project.
The project officially started on September 1st, 2001, with a total duration of 39 months. The main milestones of the project include the aforementioned two full mask sets for circuit evaluation, model verification and technology optimization taped out in May 2002 and September 2003, respectively.
Two public workshops for result dissemination are set for February 2003 and November 2004, while internal reports on models for active and passive devices are scheduled for April 2003 and November 2004. Finally, optimized CMOS devices for microwave applications should be available at the end of the project in November 2004.
The project coordinator is Goncal Badenes, Interuniversitair Micro-Electronica Centrum (IMEC), Leuven, Belgium. E-mail: Goncal.Badenes@imec. Partners: Ericsson AB, Sweden; Ericsson Microelectronics, Sweden; Philips Research Laboratories, the Netherlands; Innovative Technology Solutions, Belgium; and Chalmers University of Technology, Sweden.
MIPA - MEMS-based Integrated Phased Array Antennas
The focus is on the development of MEMS and related technologies for millimeter-wave transceivers applied to car radar systems working at 77 GHz or satellite multimedia data links in the upper Q band (40/50 GHz). The aim is that the development of MEMS-based millimeter-wave modules and their assembly to antenna front-end prototypes with redundancy power routing (space application) or phased array antenna feeding (automotive) will demonstrate the enormous innovative potential of MEMS technology in the millimeter-wave range. In order to ensure the possible widespread application of these RF MEMS-based components into commercial products, packaging and reliability issues will be specifically addressed.
The MIPA consortium comprises leading European companies in microwave product development and microsystems technology with expertise in wafer fabrication, packaging, reliability assessment and commercial exploitation.
Initial work is on the specification of MEMS devices and MEMS-based sub-modules such as redundancy switches, phase shifting devices, power routing networks, together with the specification of the assembly of these devices and modules to a space and an automotive prototype for operation at 50 and 77 GHz, respectively.
A major part of the study is the design of these devices by using electromagnetic and thermo-mechanical simulation tools to serve the wafer processing with layouts and important technology related information. The wafer processing deals with the microfabrication of single MEMS switches, their monolithic integration to yield more complex on-wafer sub-modules as phase shifters or routing networks. It entails the fabrication of on-wafer matching and bias structures, and other passive components. Therefore, a lot of technology work and development in the microsystems area will be done during the wafer processing.
With regard to the specific requirements of the space and automotive industrial sector, the work related to packaging and hermetic sealing of MEMS-based sub-modules (to protect them against impairment through environmental conditions) will constitute the largest part of the study. In particular the performance of the devices at the envisaged frequencies for operation (50 and 77 GHz) after their packaging will be investigated in depth.
To exploit MEMS devices for millimeter-wave applications, their reliability under all possible conditions must be known. Therefore, efforts will be directed towards the determination of the long-term behavior (both mechanical and electrical) of millimeter-wave MEMS in order to identify weak points in the technology and fabrication process flow. This will be done with specific regard to space and automotive conditions (vibration, temperature, humidity, etc.).
To demonstrate the potential of MEMS at millimeter-wave frequencies, MEMS-based antenna front-ends will be developed and characterized, one for a 50 GHz space communications system and one for a 77 GHz car radar. This work will be supported with the development of other millimeter-wave components, such as array antennas, in order to build MEMS-based integrated phased array prototypes.
With a scheduled duration of 36 months the project began on August 1st, 2001, and is due for completion on July 31st, 2004. At this stage the applications have been fully defined and specified, and the project is running as planned with the first run of RF MEMS ready to go into fabrication with first reliability recommendations.
The prime contractor is Olivier Vendier, Alcatel Space Industries, Nanterre, île de France, Hauts-de- Seine, France. E-mail: olivier.vendier @space.alcatel.fr. Collaborative partners: Centre National d'Etudes Spatiales (CNES), Interuniversitair Micro-Electronica Centrum (IMEC), Coventor, Robert Bosch and Universite de Rennes.
Research is vital for the future of the microwave industry worldwide. Despite current financial constraints and the consequential constriction of resources there must be investment in projects that have commercial value, with commitment to practical development in order for the industry to evolve. One of the keys to achieving this will be to foster and encourage a spirit of cooperation between research institutes, focused on concentrating resources and expertise, not only across Europe but globally.
The author would like to thank all those individuals, institutes and test houses who supplied research material for this supplement.
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