Embedded SystemsThe contemporary solutions of measurement and instrumentation are based on dedicated computer systems, and offer a wide variety of autonomous services. These services include primarily data acquisition, information processing, and control, but there are several other additional mechanisms to achieve high-quality overall performance. The majority of such applications can be considered as embedded systems due to the fact, that in addition to the sensors and the actuators, also the dedicated computer system components are invisibly embedded into the hosting environment. The role of these embedded systems is to measure or identify the behaviour of their environment, which is followed by some real-time computations to provide proper characterization, influence and control.The Department of Measurement and Information Systems operates seven smaller laboratories working on problems related to various kinds of embedded systems, and hosts the Embedded Information Technology Research Group of the Hungarian Academy of Sciences and the Budapest University of Technology and Economics.

Calibration Instruments Laboratory

Research interest: current, voltage, impedance measurement, self-calibrating instruments, calibration of instrument transformers, artificial impedances.Staff: István Zoltán, associate professor, Zoltán Benesóczky, András Görgényi, Balázs Vargha, senior lecturers, József Dudás, engineer, Zoltán Román, and Zsolt Szepessy as PhD students.Resources and infrastructure: DC-Calibrator, AC-Calibrator, CT-Calibrator, VT-Calibrator, Standard CTs, Impedance Analyzer.Major research and development projects:The Department has a great tradition in research and development of precision electrical measurements and metrology including the complete innovation process. The main fields of the research activity:

Current, voltage, impedance and power measurement

Self-calibrating, self-correcting instruments Calibration of instrument transformers Artificial impedances

Since the appropriate reference standards did not exist, or were not available, the high precision instruments developed between 1980 and 1990 served mainly calibration purposes. From the beginning of the 90's, the rapid development of the analogue, digital and mixed signal processing opened new possibilities in instrumentation. Thanks to this advancing hardware and software tools, the calibration functions of the devices could be integrated into the measuring instruments, and even the automatic self-correction of the errors measured during the self-calibration process became possible. Based on these methods the following typical errors became manageable:

the errors of approximation calculable errors measurable errors errors caused by influence quantities thermal drift

Thanks to this approach the overall accuracy of the instruments can be even 1000-times better than that of the built-in components. This possibility basically changes the principles of development of measuring instruments.From the beginning of the 90's, more and more PhD students became involved in the research of self-calibrating and self-correcting measuring instruments in the following topics:

Artificial impedances Self-calibrating amplifiers Correction of thermal dynamic errors Impedance analysis Calibration Algorithm for Current-Output

R-2R Ladders Calibration of power measuring instruments

The self-calibrating and self-correcting measuring instruments provide the possibility of low-cost and efficient remote calibration via Internet, foreseeing already the technology of the third millennium in precision measurement and metrology. The growing development-, manufacturing-, marketing-, and after sales service requirements related to the new, advanced calibration instruments required a more appropriate organisation, thus in 1997 the CALIN Electronics Ltd. was established.Parallel to this, the co-operation with the Department was successfully continued by CALIN Electronics Ltd. As a result of the common efforts, in 1998 a new advanced generation of self-calibrating and self-correcting measuring

instruments has been introduced to the international market. These instruments are used as national standards and also for automatic calibration in manufacturing of current and voltage transformers in Austria, Brazil, England, Germany, Hungary, Romania, and Taiwan.

Some recent products:

Figure 1. Instrument Transformer Analyzer composed of 1 ppm calibrator and programmable

high-power artificial impedance with 101442 settings

Figure 2. 1 ppm Standard Current Transformer used in the 0.5….10000 A current range

Figure 3. Standard Additional Burden for voltage transformer calibration

Figure 4. Standard Current Transformer for calibration of watthour meters

Acknowledgement: The staff of the laboratory wishes to express his appreciation to the former contributors: László Schnell, Endre Tóth, Péter Osváth, Gyula Korányi, Péter Pataki, Ferenc Nagy, Zoltán Reguly, László Naszádos, László Gyöngy, Erik Bohus.

Contact person: István Zoltánizoltan@mit.bme.huwww.mit.bme.hu/~izoltan/

Selected publications:

1. Zoltán, I., “A Multi-Function Standard Instrument for Current Transformer Calibration,” OIML, Bulletin, Vol. XXXVI, No. 4, October 1995, pp. 28-32.

2. Zoltán, I., “Impedanzsynthese,” Technisches Messen 68 (2001) 4, Oldenbourg Verlag, Munich, Germany, pp. 179-181.

3. Vargha, B. and I. Zoltán, “Calibration Algorithm for Current-Output R-2R Ladders,” IEEE Trans. on Instrumentation and Measurement, Vol. 50, No. 5, October 2001, pp. 1216-1220.

4. Szepessy, Zs. and I. Zoltán, “Thermal Dynamic Model of Precision Wire-Wound Resistors,” IEEE Trans. on Instrumentation and Measurement, Vol. 51, No. 5, October 2002, pp. 930-934.

Biomedical Engineering Laboratory

Research interest: electronic biomedical instruments, biosignal processing, marker-based movement analysis, home health monitoring.www.mit.bme.hu/~jobbagy/biomed Staff: Ákos Jobbágy, associate professor, András Görgényi, senior lecturers, Károly Bretz jr., PhD student.Education: Biomedical Instrumentation, Electronic Measuring Equipment, Project Laboratory and Thesis work for Biomedical Instrumentation.Resources and infrastructure: passive marker-based motion analysers: PRIMAS (precision 3D) and PAM (simple 2D), electronic biomedical instruments: (ECG, PPG, blood-pressure monitors, pulmonary analyser), battery operated (scope meters, hand-held DMMs) and bench-top electrical instruments.Major research and development projects: Movement analysis: “Development of signal processing algorithms to compensate the non-ideal projection of passive marker-based motion analysers,” financed by NWO and OTKA. (See: www.mit.bme.hu/

~jobbagy/parkinson/parkinson.htm,~jobbagy/cdreklam/Markerbasedma.html)

Diagnosis and staging of patients with neural diseases is challenging, especially in the early phase. Passive marker-based motion analysis helps the objective assessment providing information about the movement of body segments during well-defined hand- and finger movements. We developed different feature extraction methods to evaluate the movement and thus the actual performance of the tested persons. These tests help in the early diagnosis of Parkinson's disease as well as in setting the appropriate medication of patients. Our tests confirmed that Parkinson's disease manifests itself uniquely in the movement disorders of a patient. A simple and cheap image-based motion analyser (PAM) has been developed at the Department that is affordable for routine clinical use. We offer also the programs that evaluate the performance of tested persons, taking into account the regularity and the speed of the movements.Partners: E. Hans Furnée, TU Delft, Péter Harcos, Szt. Imre Hospital, Emil Monos, Semmelweis University, Gábor Fazekas, Szt. János Hospital, OORI.

Figure 5. Marker trajectories during the finger-tapping test. Performance of the right and left hand of a healthy subject (above) and a newly diagnosed

Parkinsonian (below).

Home health monitoring: “Artificial patient and model in medical informatics,” financed by FKFP, and “Home health monitoring,” financed by OTKA.World life expectancy more than doubled over the past two centuries, a further increase is estimated. National health care systems should be accommodated; the prevalence rates of many diseases substantially change over age. The average medical expenditure per person is significantly higher for the elderly than for younger people.Keeping the healthiness of the population can be helped by home health monitoring. Many diseases can be treated more effectively and at a lower cost if early signs are detected. In Hungary cardiovascular diseases are the leading cause of death, being responsible for about half of the deaths [www.bel2.sote.hu/hipertonia]. It is estimated that 30% of the Hungarian population has hypertonia, above age 65 this ratio increases to approximately 65%. Diagnosis in the early stage would make it possible to start medication and treatment to prevent the deterioration of the patients.The presently existing blood-pressure meters either require trained operator or do not assure accurate measurement. Automatic and semi-automatic blood-

pressure meters are simple-to-use thus widespread in home health monitoring. However, their results are not accurate and reproducible enough, the reliability of self-assessment is not satisfactory, medical doctors have reservations for the results. The best grade (A) in the British Hypertension Society standard allows 40% of the results deviate from the reference by more than 5 Hgmm, 15% of the results by more than 10 Hgmm and 5% of the results by more than 15 Hgmm. The aim of our research work has been to increase the accuracy and reproducibility of the indirect, cuff-based blood pressure measurement with the help of the photoplethysmographic (PPG) signal. A method has been developed to measure the systolic and diastolic pressure and not the mean pressure as it is done while using the oscillometric method. A patient monitoring device is being developed that is able to store daily physiological measurement results (blood pressure, 10-s ECG recording) for 2 months. The device is also able to analyse the recorded data and request help if needed via mobile phone.Partners: Gábor Halász (BUTE, Faculty of Mechanical Eng.), Márk Kollai (Semmelweis University).

Contact person:Ákos Jobbágyjobbagy@mit.bme.huwww.mit.bme.hu/~jobbagy/

Selected publications:1. Jobbágy, Á., L. Gyöngy, E. Monos,

“Quantitative evaluation of long-term locomotor activity of rats,” IEEE Trans. on Instrumentation and Measurement, Vol. 51, No. 2, Apr. 2002, pp. 393-397.

2. Jobbágy, Á, E.H. Furnée, P. Harcos, M. Tárczy., “Early detection of Parkinson's disease through automatic movement evaluation,” IEEE Engineering in Medicine and Biology Magazine, Vol. 17, No. 2, March-Apr. 1998, pp. 81-88.

3. Jobbágy, Á, “Photoplethysmographic Signal Aids Indirect Blood-Pressure Measurement,” Proc. of MEDICON 2001, IX.  Mediterranean Conf. on Medical and Biological Engineering and Computing, 12-15 June 2001, Pula, Croatia, pp. 262-264.

Computer Networks LaboratoryResearch interest: communication of embedded systems, sensor networking, real-time and distributed communications, quality of service, wireless networking. http://www.mit.bme.hu/projects/iiensorStaff: Csaba Tóth, senior lecturer, Tamás Kovácsházy lecturer, László Kádár and Balázs Scherer research assistants. Education: Multimedia Networking, Informatics, Project Laboratory and Thesis works for Embedded Systems.Resources and infrastructure: two laboratories, PC-based development systems for PIC (8 bit) and ARM (32 bit) micro-controllers, a sample network of voice over IP telephony (made by Siemens), IEEE 802.11bg wireless network, Gigabit Ethernet Cluster, 10/100Base-T networking components including switches, routers, firewalls etc.Major research and development projects:Gigabit Ethernet Cluster: Workpackage of NEXT TTA – High Confidence Architecture for Distributed Control Applications, EU IST-2001-32111 Programme. http://www.mit.bme.hu/projects/isensor/NEXTThe Gigabit workpackage explored the achievable performance and the limitations and bottlenecks of a TTA network composed of commercial off-the-shelf high-end state-of-the-art hardware components. In The objective of NEXT TTA project was to develop,

Figure 6. Network Laboratory I.(NEXT TTA Gigabit Ethernet Cluster)

and implement novel algorithms, tools, and components to provide a generic architecture for safety-critical applications in different application domains (e.g., aerospace, automotive, and railway applications). NEXT TTA project was an integration of many different problem solutions that have been explored independently over many years in different research institutions.The Gigabit workpackage explored the achievable performance and the limitations and bottlenecks of a TTA network composed of commercial off-the-shelf high-end state-of-the-art hardware components. In particular, the workpackage set-up a TTA cluster consisting of ordinary PCs, which are the nodes of the cluster, and a Gigabit Ethernet serving as the interconnection network. All the components could be purchased at the " next door computer shop". Our workpackage implemented a Windows-based host for this TTA cluster, and analysed the whole system by measuring its performance and attributes.Industrial application of modern info-communications technology (IKTA 164/2000 –Sponsored by the Hungarian Ministry of Education.) Co-operation with VERTESZ Kft.http://www.mit.bme.hu/projects/isensor/IKTA2000During the last five years a remarkable spreading of high-level communication technologies, principally the Ethernet and internet, was noticeable in the embedded system market. As a result, most of the leading embedded system manufacturers have started offering solutions to connect their devices into TCP/IP protocol based computer networks, unfortunately, using non-standard protocols in the application layer.The goal of this project was to review the applicable internet protocols and system architectures, to describe a solution for developing network capable smart sensors and actuators, with good system integration ability.

Figure 7. Network Laboratory II.

http://rten.mit.bme.hu/projects/isensor/ICCC2003We have developed an SNMP-based pseudo NCAP (based on IEEE 1451) providing a transducer independent network accessible interface, useable to formalise the control of devices with different functions. http://rten.mit.bme.hu/projects/isensor/IMTC2003Contact person: Csaba Tóth toth@mit.bme.huhttp://www.mit.bme.hu/~toth/

Selected publications: 1. Cs. Tóth, B. Scherer, L. Kádár, T. Bakó:

Implementation possibilities of networked smart transducers, ICCC 2003, International Carpathian Control Conference, Tatranska Lomnica, Slovak Republic, 26-29 May 2003, pp. 198-201.

2. B. Scherer, Cs. Tóth, T. Kovácsházy., B. Vargha: SNMP-Based Approach to Scalable Smart Transducer Networks, IMTC 2003, IEEE Instrumentation and Measurement Technology Conference, Vail, Colorado, USA, 20-22 May 2003, pp. 721-725.

3. Tamás Kovácsházy, Róbert Szabó, Performance Measurement Tool for Packet Forwarding Devices, 2001 IEEE Instrumentation and Measurement Technology Conference IMTC 2001, Budapest, Hungary, 2001, Vol. 2., pp. 860-863,

4. T. Péter, Cs. Tóth, Quality of System Monitoring in a Complex Internet Service Provider - Case study. IEEE International Conference on Intelligent Engineering Systems (INES’99), Slovakia, Nov. 1-3, 1999, pp. 629-633.

Logic Design LaboratoryResearch interest: digital system design, high level synthesis, advanced signal and image processing architectures, embedded microprocessor systems, dynamically reconfigurable computers, and system on a programmable chip implementations.Staff: Béla Fehér, Gábor Horváth, associate professors, Lőrinc Antoni, research assistant, Péter Szántó PhD student. Education: The laboratory has a central role in the practical education of the students of the Embedded Systems Branch. Our open laboratory policy makes

the lab to a familiar working place not only for the curricula lectures, but also for the elaboration of the particular student ideas as well. Subjects related to the laboratory are Digital Technique, Logic Design, Microprocessor Systems, Design of SoPCs by FPGAs, student project and thesis works. Resources and infrastructure: The laboratory is equipped with 12 PCs, configured as W2000 workstations. All important design software’s are available in the laboratory, including the Xilinx ISE and EDK FPGA development system, the Matlab Environment, the Mentor Graphics ModelSim, FPGA Advantage, SystemVision, Seamless and Celoxica Handel-C tools. Tektronix TPA 700 LA or ARM MultiICE IDE development boards from Digilent and XESS are also available. Major research and development projects: The Logic Design laboratory is the centre of the department’s research work for the design of complex digital systems, with emphasis on the application of FPGAs and exploitation of the re- configurability. Significant results were achieved with the application of FPGAs in the field of digital signal processing. Different basic linear FIR and IIR filter structures, DSP core generators, and efficient finite word and distributed arithmetic building blocks were developed [1]. Based on special recursive algorithm, high performance 1D and 2D linear transform modules (WHT, DCT) were implemented in an area optimized way [2]. Similar methods were used later to implement nonlinear median filters as well, for high speed video signal processing. Current research is focused on FPGA implementation of advanced 3D rendering algorithms for portable applications with reconfigurable computing architectures [3].

Figure 8. 48 tap, 16 bit FIR filter in a 5k gates FPGA

Figure 9. LOGSYS-BLOXES FPGA Educational

Board

Significant work has been done to offer a modular FPGA/PLD development board family for the students, called LOGSYS-BLOXES. Three levels of boards has been made, supporting the different needs of the education in the basic, entry level logic design, and later on the implementation of more complex DSP and communication units and system on a chip development and verification. A simple, standardized USB-based debugger, control and power interface is also provided with a rich set of interesting peripheral interface modules. Unique property of dynamic reconfiguration (DRC) capability of some SRAM technology based FPGAs makes possible very special applications, for example the dependability and fault tolerance analyses of complex digital systems. DRC is used to inject Single Event Upset (SEU) or stuck-at-1 (or 0) like errors into the logic and evaluate the behaviour in real time [4]. This research was done in cooperation with Prof. Régis Leveugle, TIMA, France. Efficient arithmetic modules were also developed exploiting the DRC, in frame of the national FKFP project Re-configurable Computing Architectures (0413/1997). Partners were University of Veszprém and University of Miskolc. The Logic Design Laboratory also serves as a Technology Expertise Center (TEC) in different national and EC projects. It offers consultation and design services for SMEs interested in advanced embedded system design methodologies. The EC funded FP5 technology transfer project JENET (Joint European Network of Embedded Internet Technologies, IST IST-2000-28422) is a good example of these activity. JENET is promoting the use of the new communication capabilities in industrial applications, specifically the embedded

Figure 10. JENET presentation,Magyar Regula, 2003.

internet technology in products and systems developed by European enterprises. JENETis carried out by a network of 7 TECs and 27 User Companies (UCs) from Belgium, Germany, Hungary, Italy, Poland, Romania and United Kingdom. Local partner SMEs are Infoware Co., Meldetechnik Ltd., Silex Ltd., and the project coordinator is CRR, Italy. More information: http://www.eurojenet.com.

Contact Person: Béla Fehér feher@mit.bme.hu http://www.mit.bme.hu/~feher/

Selected publications:1. Fehér, B., “Efficient Synthesis of

Distributed Vector Multipliers,” Journal of Microprocessors and Microprogramming, Vol. 38. No. 1-5. 1993.

2. Fehér, B., “ New Inner Product Algorithm of the 2D DCT,” Digital Video Compression: Algorithm and Technologies, Proc. SPIE, Vol. 2419. ISBN 0-8194-1766-1.

3. Szantó, P. and B. Fehér, “3D Rendering using FPGAs,” IFIP International Conference on VLSI SOC, December 1-3, 2003 Darmstadt, Germany.

4. Antoni, L., R. Leveugle, B. Fehér, “Using run-time reconfiguration for fault injection applications,” IEEE Trans. on Instrumentation and Measurement, Vol. 52, No. 5, October 2003.

Digital Signal Processing LaboratoryResearch interest: Signal modelling, adaptive signal processing, digital filter structures, transform-domain signal processing. Signal processing in complex measurement systems. Staff: László Sujbert, László Naszádos senior lecturers, Balázs Bank, research assistant, Károly Molnár PhD. student. Part-time contributors: Gábor Péceli, professor, Tamás Dabóczi, associate professor, Gyula Simon, senior lecturer. Education: Embedded systems laboratory, Information systems laboratory, Project laboratory. Resources and infrastructure:

DSP development boards (Analog Devices, Motorola, Texas Instruments)

Vibro-acoustic transducers, signal conditioners (Brüel&Kjaer)

Digital storage scopes, spectrum analyzers, special generators (LeCroy, HP)

Major research and development projects:Active noise control is an old idea for acoustic noise suppression, but it could be implemented only since the advent of digital signal processors. The solution is based on the destructive interference phenomenon. We have developed a dedicated method for suppressing periodic noise components. The method is the extension of the resonator-based observer developed also at the department. The advantages of the resonator-based noise controller are its fast convergence (compared to other methods) and its low computational burden. Based on the experiences with the resonator-based periodic noise controller, we have developed a modification of the well-known filtered-X LMS algorithm

Figure 11. Typical performance of an active noise control system

allowing faster convergence for broadband noise control, as well. Grants, international relations:

OTKA: Acoustic applications of digital signal processing, F 035060

TPD-TNO Delft, the Netherlands http://www.tpd.tno.nl

Digital sound synthesis of musical instruments has been acclaimed at the department in the last years. It needs very precise measurements and poses serious signal processing problems. The results achieved in this field can be utilized generally, e.g. in system identification or in filter design. We have successfully synthesized the sound of organ, violin and piano. Most of research results were achieved for piano sound synthesis, where the digital waveguide model has been improved. Grants, international relations: OTKA: Acoustic applications of digital signal

processing, F 035060 MOSART IHP (Improving Human Potential)

Training Network, HPRN-CT-2000-00115 http://www.diku.dk/forskning/musinf/mosart

Helsinki University of Technology, Laboratory of Acoustics and Audio Signal Processing http://www.acoustics.hut.fi

University of Padua, Department of Information Engineering http://www.dei.unipd.it

One of our latest industrial projects is development of a DSP-based system for in-motion weighing of railway carriages. It is a two-level system that comprises of 16 or 24 DSP-based Measurement Units (MU) and a powerful HOST PC. The MUs store the deformation signals of the rail caused by

Figure 12. Transfer function measurement of a violin body

the wheels of an in-motion train. The deformation is measured by strain gauges. AD converters sample the signal of the strain gauge bridge, and this signal is processed at the DSP. The HOST collects the stored data, and a large database is built for each train. Contact person:László Sujbertsujbert@mit.bme.huwww.mit-bme/~sujbert/

Selected publications:1. Sujbert, L., and G. Péceli, “Signal model

based periodic noise controller design,” Measurement - the Journal of the IMEKO, vol. 20, No. 2, pp. 135-141.

2. L. Sujbert, “A new filtered LMS algorithm for active noise control,” Proc. of the Active '99 - The International EAA Symposium on Active Control of Sound and Vibration, Dec. 2-4, 1999, Fort Lauderdale, Florida, USA, pp. 1101-1110.

3. Bank, B., and Vesa Välimäki, "Lobust Loss Filter Design for Digital Waveguide Synthesis of String Tones," IEEE Signal Processing Letters, vol. 10, No. 1, pp. 18-20, Jan. 2003.

Chaotic Signals and Systems Laboratory

Research interest: Chaotic communication systems, analysis and computer simulation of data communication systems, frequency synthesis, phase-locked loop. http://www.mit.bme.hu/research/chaos/Staff: Géza Kolumbán, associate professor, Gábor Kis, Zoltán Jákó, research assistants, Zoltán Szabó, Béla Frigyik, PhD students.Education: Electronics I and II, Theory and Applications of Nonlinear Theory and Chaos (PhD course), System Level Design and Analysis. Project Laboratory works and MS Theses.Resources and infrastructure: Linux-based PCs.Major research and development projects:Development and analysis of novel signal processing architectures for system-on-a-chip (SoC) integrated circuits, T038083, financed by OTKA (2002-2005).The project has been launched to find new transceiver and frequency synthesizer configurations for communication and measurement purposes.

Partners: Prof. G. Chen (City University of Hong Kong; Profs. C.M. Lau and C.K. Tse, The Hong Kong Polytechnic University.Innovative signal processing exploiting chaotic dynamics (INSPECT), Esprit Project 31103, Open LTR – 2nd phase, Financed by European Commission, 1998-2001.http://www.cordis.lu/esprit/src/31103.htm, http://www.mit.bme.hu/research/chaos/inspect/ Chaotic signals are inherently wideband signals that can be generated with high power efficiency using simple nonlinear circuits in any frequency band and at arbitrary power level. In chaotic communications, the digital information to be transmitted is mapped directly into a wideband chaotic waveform. Chaotic communication offers a low cost alternative solution to conventional spread spectrum communication.Seven European universities collaborated in the INSPECT Esprit Project to find applications for chaotic signals in communication and watermarking of digital pictures. The Chaotic Systems Team coordinated the research and implementation of a working prototype of frequency-modulated chaos-shift keying (FM-DCSK) communication system. We have invented FM-DCSK (the most robust chaotic modulation scheme), derived exact expressions for the noise performance of correlator-based chaotic modulation schemes, developed an ultra fast computer simulator to evaluate the system performance of digital communication systems under various channel conditions, elaborated the system proposal and determined the system level parameters for the INSPECT FM-DCSK chaotic data communications system.The INSPECT FM-DCSK radio shown in Fig 13 operates in the 2.4-GHz ISM band and was successfully tested in 2001. To illustrate its excellent multipath performance, the bit error rate (BER) curves of conventional differential phase-shift keying (DPSK) and chaotic FM-DCSK are compared in Fig. 14. Although the single-ray performance of FM-DCSK is worse than that of DPSK, in the indoor multi-path channels the DPSK fails completely (see dash-dotted curve) while FM-DCSK has only a 4-dB loss in the system performance (see dashed and dotted curves).Our direct partner in the INSPECT Project was Prof. M.P. Kennedy, University College Dublin.Spread spectrum communication exploiting chaos, Office of Naval Research (ONR), USA, 1995-1996.

Figure 14. BER curves of conventional DPSK and chaotic FM-DCSK in a single-ray additive white

Gaussian noise (AWGN) channel (solid and dashed, respectively) and in an indoor multi-path channel

(dash-dotted and dotted, respectively.

The goal of this project was to propose an underwater chaotic communication scheme for the submarines of US Navy. In the project we have elaborated a comprehensive theory for chaotic waveform communications.Partners: Prof. L.O. Chua, University of California, Berkeley, and Prof. M.P. Kennedy, University College Dublin.

Contact person: Géza Kolumbán, kolumban@mit.bme.huwww.mit.bme.hu/~kolumban/

Selected publications:1. Kolumbán, G., M.P. Kennedy, Z. Jákó and G.

Kis, “Chaotic communications with correlator receiver: Theory and performance limits,” invited paper in Proceedings of the IEEE, vol. 90, pp. 711-732, May 2002.

2. Kennedy M.P., and G. Kolumbán, guest editors, Special Issue on “Noncoherent Chaotic Communications,” IEEE Trans. Circuits and Syst. I, vol. 47, pp. 1661-1732, December 2000.

3. Kolumbán, G., M.P. Kennedy and L.O. Chua, “The role of synchronization in digital communications using chaos,” IEEE Trans. Circuits and Syst. I, Part I: “Fundamentals of digital communications,” 44(10): 927-936, October 1997; Part II: “Chaotic modulation and chaotic synchronization,” 45(11): 1129-1140, November 1998; Part III: “Performance bounds,” 47(12): 1673-1683, December 2000.

4. G. Kolumbán, “Theoretical noise performance of correlator-based chaotic communications schemes,” IEEE Trans. Circuits and Syst. I, vol. 47, pp. 1702-1711, December 2000.

5. G. Kolumbán, “The theory and implementation of a robust chaotic digital communications

system,” invited talk at 2003 Microwave Symposium Workshop, IEEE International Microwave Symposium, Philadelphia, USA, June 2003. www.ims2003.org/technical/workshop/ WMA.htm

Figure 13. Picture of the 2.4-GHz FM-DCSK prototype receiver built in the framework of INSPECT Esprit Project.

System Identification LaboratoryResearch interest: identification of linear systems, parameter estimation, SISO/MIMO modelling, effect of nonlinear disturbances, signal reconstruct-tion using known measurement system models (inverse filtering).Staff: István Kollár, professor, Tamás Dabóczi, associate professor, Gyula Simon, senior lecturer, József Németh, research assistant, László Balogh, János Márkus, Balázs Vödrös, PhD students, Zoltán Bilau, graduate student.Education: Digital signal processing, System identification, Embedded systems, Project Laboratory, and Diploma thesis design.Major research and development projects: Identification in the Frequency DomainThe close cooperation between our department, and the Department ELEC at the Vrije Universiteit Brussel, Belgium (http://wwwtw.vub.ac.be/elec/), is continuous since 1989. One of the major results of this cooperation is the Frequency Domain System Identification Toolbox for MATLAB. The peculiarity of the frequency domain methods is that they solve the maximum likelihood equations in the frequency domain, making it possible to fully exploit the advantages of harmonic excitations.An important step in identification is the validation of the results. We always have to check whether the result really satisfies our requirements, is in no contradiction with the preliminary assumptions, and corresponds to the data. A program can only offer tools for this purpose: the validation itself is the task of the person who performs the identification.

The toolbox effectively uses the following advanced MATLAB tools:

graphical user interface, automatic procedures, and data structures.

The investigated system can be anything from electrical systems (filters, machines) to mechanical systems (airplanes, cars, robot arm) and acoustical systems (airplane cabin, loudspeaker), etc.The toolbox is now in use throughout the world. Linear modelling is currently being extended to characterize slight nonlinear distortions, and to model multiple input – multiple output systems.Inverse filteringThe accuracy of time domain waveform measurements is limited by the finite bandwidth of the measurement instrument. This means that high frequency components of the signal will be suppressed and the phase of the different frequency components will be modified. The result is a

Figure 15. Compare and Evaluate Models window of the GUI of the fdident toolbox

distorted waveform; the fast changes of the signal are rounded, rapid transitions are stretched out. Digital post-processing of the measured data can improve the result. This is called inverse filtering. This problem is usually ill-posed, that is, small changes in the measured output signal cause large fluctuations in the estimation of the input signal.Different inverse filtering techniques provide different approaches to suppress the amplified noise without significantly distorting the useful signal.Successful applications of inverse filtering: High voltage lightning measurements:

compensating the distortion of high voltage dividers. Cooperating party: Swiss Federal Institute of Technology, Zürich, Switzerland, High Voltage Laboratory

Calibration of ultra high-speed oscilloscopes. Cooperating party: National Institute of Standards and Technology, NIST, USA

Restoration the sound of old movies, kept on film

Figure 16. Measured and reconstructed high voltage lightning impulses

Figure 16. High voltage lightning impulse measurement setup

High voltage generator, chopping gap and high voltage dividers – HV laboratory of the ETH ZürichRecent Research Grants: OTKA (Hungarian Scientific Research Fund), NIST (National Institute of Standards and Technology, USA), Hungarian Ministry of Education.Contact persons:

István Kollár Tamás Dabóczi

kollar@mit.bme.hu daboczi@mit.bme.hu www.mit.bme.hu/~kollar/ .../~daboczi/

Selected publications: 1. FDIDENT (1999-2003), Frequency Domain

System Identification Toolbox Developers’ Page. http://elec.vub.ac.be/fdident/

2. Kollár, I., R. Pintelon, Y. Rolain, J. Schoukens, and Gy. Simon, “Frequency Domain System Identification Toolbox For MATLAB: Automatic Processing – From Data To Models.” IFAC Symposium on System Identification, SYSID 2003, Aug. 2003, Rotterdam.

3. Dabóczi, T., I. Kollár, Gy. Simon, and T. Megyeri, “How to Test Graphical User Interfaces?” IEEE Instrumentation and Measurement Magazine, Vol. 6, No. 3, pp. 27-33, Sep. 2003.

4. Deyst, J. P., N. G. Paulter, T. Dabóczi, G. N. Stenbacken, T. M. Souders, "A Fast Pulse Oscilloscope Calibration System," IEEE Trans. on Instrumentation and Measurement, Vol. 47, No. 5, pp. 1037-1041, 1998.