Dr.-Ing. Gerhard Olbrich


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Technical University of Munich

Chair of High-Frequency Engineering (Prof. Eibert)

Curriculum Vitae

Gerhard R. Olbrich received his Dipl.-Ing. degree in 1974 and his Dr.-Ing. degree in 1979, both in electrical engineering from the Technische Universität München, Germany.

From 1975 to 1985 he was Assistant Professor at the Institute of Microwave Engineering and later on at the Institute of High Frequency Engineering at the Technische Universität München. During this time he worked on problems of microwave S-parameter and frequency measurements and planar hybrid circuits using thinfilm technology up to 90 GHz.

From 1986 to 1988 Dr. Olbrich was president of Work Microwave GmbH, Holzkirchen, Germany, mainly engaged in developing low phase noise microwave oscillators.

Since 1989 he has again been with the Institute of High Frequency Engineering of the Technische Universität München and is now Director of Research (Akademischer Direktor). His current interests are in the fields of RF and microwave measurement techniques, active and passive device modeling, planar hybrid and integrated circuits, and low phase noise oscillators. The investigated frequency range reaches up to 110 GHz. Dr. Olbrich has served as a member of paper review boards and steering committees of various international conferences. Dr. Olbrich is a member of the IEEE and of the German Informationstechnische Gesellschaft VDE (ITG).

Research

  • RF and microwave S-parameter measurement techniques, (koaxial, waveguide and on-wafer)^
  • low frequency and high frequency noise measurements
  • large signal and noise modelling of active (MESFET, HEMT, BJT, HBT ...) and passive devices up to 60 GHz
  • investigations on nonlinear circuits, especially oscillators for RF and microwaves

Publications

2008

[1] Tobias Hermann, Gerhard R. Olbrich and Peter Russer: (doi)
A Novel System for Real-Time Measurement of the Electrical Properties of a Cavity Resonator
38th European Microwave Conference (EuMC), Amsterdam, The Netherlands, pages 67 - 70, October 2008.
[2] Tobias Hermann, Gerhard R. Olbrich and Peter Russer: (doi)
A Novel Microwave-based Inspection System for Continuously Streaming Materials Using a Cavity Resonator
38th European Microwave Conference (EuMC), Amsterdam, The Netherlands, pages 901 - 904, October 2008.

2007

[1] Robert Wanner, Rudolf Lachner, Gerhard R. Olbrich and Peter Russer: (doi)
A SiGe Monolithically Integrated 278 GHz Push-Push Oscillator
IEEE MTT-S International Microwave Symposium, Honolulu, HI, USA, pages 333 - 336, June 2007.

2006

[1] Robert Wanner, Rudolf Lachner and Gerhard R. Olbrich: (doi)
A SiGe Monolithically Integrated 75 GHz Push-Push VCO
Digest of Papers of Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, San Diego, CA, USA, pages 375 - 378, January 2006.
[2] Robert Wanner, Rudolf Lachner and Gerhard R. Olbrich: (doi)
Monolithically Integrated SiGe Push-Push Oscillators in the Frequency Range 50-190 GHz
IEEE Ninth International Symposium on Spread Spectrum Techniques and Applications (ISSSTA), Manaus, Amazon, Brazil, pages 26 - 30, August 2006.
[3] Robert Wanner, Rudolf Lachner and Gerhard R. Olbrich: (doi)
SiGe Integrated mm-Wave Push-Push VCOs with Reduced Power Consumption
IEEE Radio Frequency Integrated Circuits (RFIC) Symposium, San Francisco, CA, USA, pages 483 - 486, June 2006.

2005

[1] Robert Wanner, Rudolf Lachner and Gerhard R. Olbrich: (doi)
Low phase noise SiGe push-push oscillators for cm- and mm-wave applications
17th Asia-Pacific Microwave Conference (APMC), Suhzhou, China, Vol. 2, pages 1075 - 1078, December 2005.
[2] Robert Wanner, Rudolf Lachner and Gerhard R. Olbrich: (doi)
A monolithically integrated 190-GHz SiGe push-push oscillator
IEEE Microwave and Wireless Components Letters, Vol. 15, No. 12, pages 862 - 864, December 2005.
[3] Robert Wanner, Herbert Schäfer, Rudolf Lachner, Gerhard R. Olbrich and Peter Russer:
A fully integrated SiGe low phase noise push-push VCO for 82 GHz
European Gallium Arsenide and Other Semiconductor Application Symposium (EGAAS), Paris, France, pages 249 - 252, October 2005.
[4] Robert Wanner, Herbert Schäfer, Rudolf Lachner, Gerhard R. Olbrich and Peter Russer:
A SiGe Low Phase Noise Push-Push VCO for 72 GHz
XXVIIIth General Assembly of the International Union of Radio Science (URSI), New Delhi, India, October 2005.
[5] Robert Wanner, Herbert Schäfer, Rudolf Lachner, Gerhard R. Olbrich and Peter Russer: (doi)
A fully integrated 70 GHz SiGe low phase noise push-push oscillator
IEEE MTT-S International Microwave Symposium, Long Beach, USA, pages 1523 - 1526, June 2005.
[6] Jung Han Choi, Gerhard R. Olbrich and Peter Russer: (doi)
An Si Schottky Diode Demultiplexer Circuit for High Bit-Rate Optical Receivers
IEEE Transactions on Microwave Theory and Techniques, Vol. 53, No. 6, pages 2033 - 2042, June 2005.

2004

[1] Jung Han Choi, Gerhard R. Olbrich and Peter Russer:
A Sampler-Based ETDM Optical Receiver Using Si Schottky Diodes
34th European Microwave Conference (EuMC), Amsterdam, The Netherlands, Vol. 1, pages 515 - 518, October 2004.
[2] Robert Wanner, Gerhard R. Olbrich, H. Jorke, Johann-Friedrich Luy, Sandra Heim, Erich Kasper and Peter Russer: (doi)
Experimental Verification of the Resonance Phase Transistor Concept
IEEE MTT-S International Microwave Symposium, Philadelphia, PA, USA, Vol. 2, pages 991 - 993, June 2004.
[3] Tuan Do-Hong, Gerhard R. Olbrich and Peter Russer: (doi)
Reduction of Complexity for Digital Beamforming in High-Altitude-Platform and Satellite Systems
IEEE MTT-S International Microwave Symposium, Philadelphia, PA, USA, Vol. 2, pages 1245 - 1248, June 2004.
[4] Tuan Do-Hong, Gerhard R. Olbrich and Peter Russer: (doi)
Smart Antenna Technology for High-Altitude-Platform Based Wireless Communication Systems
15th International Conference on Microwaves, Radar and Wireless Communications (MIKON), Warsaw, Poland, Vol. 2, pages 645 - 648, May 2004.
[5] Jung Han Choi, Gerhard R. Olbrich and Peter Russer:
A novel ETDM Optical Receiver Circuit using Si Schottky Diodes
9th Scientific Exchange Seminary, Lehrstuhl für Hochfrequenztechnik, Munich, Germany, pages 3 - 6, September 2004.
[6] Tuan Do-Hong, Gerhard R. Olbrich and Peter Russer: (doi)
A New Digital Beamforming Scheme for High-Altitude-Platform Based Communication Systems
ITG Workshop on Smart Antennas, Munich, Germany, pages 63 - 68, May 2004.
[7] Tuan Do-Hong, Gerhard R. Olbrich and Peter Russer:
A Smart Antenna Scheme for High-Altitude-Platforms in Future Wireless Communication Systems
6th Annual Wireless and Microwave Technology Conference Digest (WAMI), Clearwater, FL, USA, April 2004.
[8] Robert Wanner, M. Pfost, R. Lachner and Gerhard R. Olbrich: (doi)
A 47 GHz Monolithically Integrated SiGe Push-Push Oscillator
Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, Atlanta, GA, USA, pages 9 - 12, September 2004.

2003

[1] Jung Han Choi, C.-J. Weiske, Gerhard R. Olbrich and Peter Russer: (doi)
Flip-Chip Bonded Si Schottky Diode Sampling Circuits for High Speed Demultiplexers
IEEE MTT-S International Microwave Symposium, Philadelphia, PA, USA, Vol. 3, pages 1515 - 1518, June 2003.
[2] Robert Wanner and Gerhard R. Olbrich: (doi)
A Hybrid Fabricated 40 GHz Low Phase Noise Sige Push-Push Oscillator
Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, Grainau, Germany, pages 72 - 75, April 2003.
[3] Luca Marcaccioli, Gerhard R. Olbrich, Stefan Lindenmeier and Roberto Sorrentino: (doi)
Planar Microstrip Diplexer for Multifunctional Antenna
33rd European Microwave Conference (EuMC), Munich, Germany, Vol. 3, pages 919 - 922, October 2003.
[4] Jung Han Choi, C.-J. Weiske, Gerhard R. Olbrich and Peter Russer: (doi)
Si Schottky Sampling Bridge Circuits for Demultiplexer
Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, Grainau, Germany, pages 134 - 137, April 2003.
[5] Jung Han Choi, Gerhard R. Olbrich and Peter Russer:
Analog Demultiplexer Circuit Using a Flip-Chip Bonded Si Schottky Diode Sampler
EEEfCOM Innovation Preis 2003 awarded, 2003.
[6] Robert Wanner, Tobias Hermann, Gerhard R. Olbrich and Peter Russer:
Resonant Phase Transistor (RPT) Device and Circuit Simulations
33rd European Microwave Conference (EuMC), Workshop, Munich, Germany, October 2003.
[7] Franz X. Sinnesbichler and Gerhard R. Olbrich: (doi)
Thermal Time Constant Extraction for HBTs from S-Parameter Measurements
AEÜ - International Journal of Electronics and Communications, Vol. 57, No. 3, pages 181 - 184, 2003.

2002

[1] Stefan Lindenmeier, Gerhard R. Olbrich, Johann-Friedrich Luy and Peter Russer:
A Five-Band Antenna for Terrestrial and Satellite Radio Services
17th General Assembly of URSI, Maastricht, Netherlands, Vol. 4, August 2002.
[2] Gerhard R. Olbrich: (doi)
Low Phase Noise SiGe Push-Push Oscillators for V-Band Operation
3rd International Conference on Microwave and Millimeter Wave Technology (ICMMT), Bejing, China, pages 78 - 81, August 2002.

2001

[1] A. di Paola and Gerhard R. Olbrich:
Measurement and VBIC Parameter Extraction of SiGe-Transistors
11th Conference and Exhibition on Microwaves, Radio Communication and Electromagnetic Compatibility (MIOP), Stuttgart, Germany, pages 260 - 262, May 2001.
[2] Ludwig Eichinger, F. Sischka, Gerhard R. Olbrich and Robert Weigel:
Hochgenaue Modellierung eines 2GHz SAW-Oszillator Designs
ITG-Diskussionssitzung FA 9.1 Rauschmessungen für die Kommunikationstechnik, Kamp-Lintfort, Germany, October 2001.
[3] Alessandra di Paola and Gerhard R. Olbrich:
VBIC Parameter Extraction of SiGe Transistors
International Symposium on Signals, Systems, and Electronics (ISSSE), Tokyo, Japan, pages 55 - 57, July 2001.
[4] Franz X. Sinnesbichler and Gerhard R. Olbrich:
SiGe HBT Push-Push Oscillators for Millimeter-Wave Operation
International Symposium on Signals, Systems, and Electronics (ISSSE), Tokyo, Japan, pages 58 - 61, July 2001.

2000

[1] Gerhard R. Olbrich:
Nichtlineare Modellierung des Großsignal- und Rauschverhaltens von Mikrowellentransistoren
VDE-ITG-Fachausschuss 9.1 Messverfahren der Informationstechnik, München, April 2000.
[2] Franz X. Sinnesbichler and Gerhard R. Olbrich: (doi)
SiGe HBT Push-Push Oscillators for V-Band Operation
2nd Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, Garmisch-Partenkirchen, Germany, pages 55 - 59, April 2000.
[3] Martin M. Kaleja, Alexander Grübl, Franz X. Sinnesbichler, Gerhard R. Olbrich, Karl M. Strohm, Johann-Friedrich Luy and Erwin M. Biebl: (doi)
Si/SiGe HBT Active Integrated Antenna on High Resistivity Silicon Substrate
IEEE MTT-S International Microwave Symposium, Boston, MA, USA, Vol. 3, pages 1899 - 1902, June 2000.
[4] Martin M. Kaleja, Alexander Grübl, Franz X. Sinnesbichler, Gerhard R. Olbrich, Karl M. Strohm, Johann-Friedrich Luy and Erwin M. Biebl: (doi)
Application of Si/SiGe HBTs in Active Integrated Antennas
2nd Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems, Garmisch-Partenkirchen, Germany, pages 64 - 66, April 2000.
[5] Franz X. Sinnesbichler, B. Hautz and Gerhard R. Olbrich: (doi)
Low Phase Noise 58 GHz SiGe HBT Push-Push Oscillator with Simulatneous 29 GHz Output
IEEE MTT-S International Microwave Symposium, Boston, MA, USA, Vol. 1, pages 35 - 38, June 2000.
[6] Franz X. Sinnesbichler, B. Hautz and Gerhard R. Olbrich: (doi)
A SiGe HBT Dielectric Resonator Push-Push Oscillators at 58 GHz
IEEE Microwave and Guided Wave Letters, Vol. 10, No. 4, pages 145 - 147, April 2000.
[7] Ludwig Eichinger, F. Sischka, Gerhard R. Olbrich and Robert Weigel: (doi)
Accurate Design of Low-Noise Microwave SAW Oscillators
IEEE Ultrasonics Symposium, San Juan, Puerto Rico, Vol. 1, pages 129 - 134, October 2000.
[8] Franz X. Sinnesbichler and Gerhard R. Olbrich: (doi)
Accurate Large-Signal Modeling of SiGe HBTs
IEEE MTT-S International Microwave Symposium, Boston, MA, USA, Vol. 2, pages 749 - 752, June 2000.

1999

[1] Gerhard R. Olbrich:
Modelling of Low and High Frequency Noise in Active RF-Devices
6th Scientific Exchange Seminary, Moscow, Russia, April 1999.
[2] Franz X. Sinnesbichler and Gerhard R. Olbrich:
Extraction of VBIC Model Parameters for SiGe HBTs Including Thermal Effects, Self-Heating and 1/f-Noise
5th European IC-CAP User Meeting, Marseille, France, June 1999.
[3] Abraham Kaleve, Franz X. Sinnesbichler and Gerhard R. Olbrich:
1/f-Noise Parameter Extraction for Advanced Semiconductor Devices
5th European IC-CAP User Meeting, Marseille, France, pages 1 - 5, June 1999.
[4] Franz X. Sinnesbichler and Gerhard R. Olbrich:
A SiGe HBT Push-Push Oscillator for 58 GHz in Hybrid Microstrip Technique
7th International Symposium on Recent Advances in Microwave Technology (ISRAMT), Malaga, Spain, pages 489 - 492, December 1999.
[5] Franz X. Sinnesbichler, Hans Geltinger and Gerhard R. Olbrich: (doi)
A 38-GHz Push-Push Oscillator Based on 25-GHz f_T BJT's
IEEE Microwave and Guided Wave Letters, Vol. 9, No. 4, pages 151 - 153, April 1999.
[6] Abraham Kaleve, Franz X. Sinnesbichler, K. Wawrzyniak and Gerhard R. Olbrich:
Rauscharmer, integrierter VCO bei 2 GHz
Kleinheubacher Berichte, Kleinheubach, Germany, Vol. 42, September 1999.
[7] Gerhard R. Olbrich:
Characterization of Low and High Frequency Noise in Active Devices
5th International Conference on Noise in Physical Systems and 1/f-Fluctuations, Hong Kong, pages 25 - 30, August 1999.
[8] Franz X. Sinnesbichler, Hans Geltinger and Gerhard R. Olbrich: (doi)
A 50 GHz SiGe HBT Push-Push Oscillator
IEEE MTT-S International Microwave Symposium, Anaheim, CA, USA, Vol. 1, pages 9 - 12, June 1999.
[9] Franz X. Sinnesbichler and Gerhard R. Olbrich: (doi)
Electro-Thermal Large-Signal Modeling of SiGe HBTs
29th European Microwave Conference (EUMA), Munich, Germany, Vol. 2, pages 125 - 128, October 1999.

1998

[1] Franz X. Sinnesbichler, Gerhard R. Olbrich and F. Sischka:
VBIC - The Vertical Bipolar Inter-Company Model. Overview About the Model, Relationship to the Gummel-Poon Model, Parameter Extraction
5th Symposium on Nano Device Technology, Workshop on High Frequency Device/Circuit Characterization and Modeling Technology, Hsinchu, Taiwan, pages 101 - 143, May 1998.
[2] Franz X. Sinnesbichler and Gerhard R. Olbrich:
VBIC-The Vertical Bipolar Inter-Company Model. Ein Überblick über das Modell und über zugehörige Parameterextraktionen
Hewlett-Packard IC-CAP Workshop-Reihe, Munich, Germany, January 1998.
[3] Franz X. Sinnesbichler and Gerhard R. Olbrich:
Large Signal Modelling of SiGe HBTs Using the VBIC Model
6th IEEE International Workshop on High Performance Electron Devices for Microwave and Optoelectronic Applications (EDMO), Manchester, UK, pages 131 - 135, November 1998.
[4] Franz X. Sinnesbichler and Gerhard R. Olbrich:
Modellierung des Rauschens von Halbleiterbauelementen
Hewlett-Packard IC-CAP Workshop-Reihe, Munich, Germany, July 1998.
[5] Gerhard R. Olbrich:
Modeling of Active RF- and Microwave Devices
5th International Workshop on Integrated Nonlinear Microwave and Millimeterwave Circuits, Duisburg, Germany, pages 43 - 54, October 1998.
[6] Franz X. Sinnesbichler, M. Fischer and Gerhard R. Olbrich: (doi)
Accurate Extraction Method For 1/f-Noise Parameters Used in Gummel-Poon Type Bipolar Junction Transistor Models
IEEE MTT-S International Microwave Symposium, Baltimore, MD, USA, Vol. 3, pages 1345 - 1348, June 1998.
[7] F.X. Sinnesbichler and Gerhard R. Olbrich:
Large Signal and Noise Modeling of AlGaAs/GaAs-HEMT-Devices
28th European Solid-State Device Research Conference (ESSDERC), Bordeaux, France, pages 476 - 479, September 1998.

1997

[1] Gerhard R. Olbrich:
Phase Noise Analysis of a 15-GHz-HFET-Oscillator
Progress in Electromagnetics Research Symposium (PIERS), Hong Kong, pages 242, January 1997.
[2] Franz X. Sinnesbichler and Gerhard R. Olbrich:
Early Effect Modeling of Bipolar Junction Transistors with low Early Voltages
4th European IC-CAP User Meeting, Berlin, Germany, October 1997.
[3] Franz X. Sinnesbichler, Tilmann Felgentreff and Gerhard R. Olbrich: (doi)
Large Signal and Noise Modeling of HEMT Devices including Frequency and Temperature Effects
27th European Microwave Conference (EUMA), Jerusalem, Israel, Vol. 1, pages 428 - 431, September 1997.
[4] Gerhard R. Olbrich and Peter Russer: (doi)
Nonlinear Methods for Microwave Oscillator Design
27th European Microwave Conference (EUMA), Jerusalem, Israel, Vol. 2, pages 943 - 948, September 1997.

1996

[1] Tilmann Felgentreff and Gerhard R. Olbrich: (doi)
Noise Behavior of a 15-GHz-AlGaAs/GaAs-HEMT-Oscillator
IEEE MTT-S International Microwave Symposium, San Francisco, CA, USA, Vol. 2, pages 935 - 938, June 1996.
[2] Tilmann Felgentreff and Gerhard R. Olbrich: (doi)
Modeling of Low Frequency Noise Sources in HEMTs
IEEE MTT-S International Microwave Symposium, San Francisco, CA, USA, Vol. 3, pages 1743 - 1746, June 1996.

1995

[1] Tilmann Felgentreff and Gerhard R. Olbrich:
Nichtlineares HEMT-Modell mit Rauschquellen
Kleinheubacher Berichte, Kleinheubach, Germany, Vol. 38, pages 591 - 600, October 1995.
[2] Tilmann Felgentreff and Gerhard R. Olbrich:
Large Signal and Noise Modelling of HFETs
3rd Scientific Exchange Seminary, Munich, Germany, pages 54 - 57, 1995.
[3] Tilmann Felgentreff, P. Selmeier and Gerhard R. Olbrich:
Rauschverhalten eines 15-GHz-AlGaAs/GaAs-HEMT-Oszillators
Mikrowellen und Optronik (MIOP), Sindelfingen, Germany, pages 306 - 312, May 1995.
[4] Tilmann Felgentreff, Werner Anzill, Gerhard R. Olbrich and Peter Russer: (doi)
Analysis of g-r Noise Upconversion in Oscillators
IEEE MTT-S International Microwave Symposium, Orlando, FL, USA, Vol. 2, pages 947 - 950, May 1995.

1994

[1] Gerhard R. Olbrich, Tilmann Felgentreff, Werner Anzill, G. Hersina and Peter Russer: (doi)
Calculation of HEMT Oscillator Phase Noise Using Large Signal Analysis in Time Domain
IEEE MTT-S International Microwave Symposium, San Diego, CA, USA, Vol. 2, pages 965 - 968, May 1994.
[2] Tilmann Felgentreff, Gerhard R. Olbrich and Peter Russer: (doi)
Noise Parameter Modeling of HEMTs with Resistor Temperature Noise Sources
IEEE MTT-S International Microwave Symposium, San Diego, CA, USA, Vol. 2, pages 853 - 856, May 1994.

1992

[1] Gerhard R. Olbrich:
Abschätzung der Empfangsgüte von Satelliten- Empfangsanlagen
Funkschau, Vol. 252, pages 26, 1992.
[2] Gerhard R. Olbrich and T. Schenk: (doi)
A Low Phase Noise 433.92 Mhz Saw Oscillator for General Mobile Communication Applications
Asia-Pacific Microwave Conference (APMC), Adelaide, Australia, Vol. 1, pages 527 - 529, August 1992.
[3] Gerhard R. Olbrich, Peter Russer, B. Scheffler and P. Kraus:
Phasenrauscharmer 80-110 MHz Oszillator mit DDS-Referenzquelle
Kleinheubacher Berichte, Kleinheubach, Germany, Vol. 36, pages 621 - 627, October 1992.
[4] Gerhard R. Olbrich and T. Schenk:
Measurement of 1/f Noise on Microwave Transistors
URSI International Symposium on Signals, Systems, and Electronics (ISSSE), Paris, France, Vol. 1, pages 772 - 775, September 1992.
[5] Tilmann Felgentreff, Gerhard R. Olbrich and Peter Russer:
A Smallsignal Databased HEMT Model for Nonlinear Time Domain Simulation
Simulation of Semiconductor Devices and Processes, Vienna, Austria, Springer, Vol. 5, pages 269 - 272, September 1993.

1991

[1] Roland Ramisch, Gerhard R. Olbrich and Peter Russer: (doi)
A Tapped-Delay-Line Superconductive Chirp Filter in Shielded Microstrip
IEEE Transactions on Microwave Theory and Techniques, Vol. 39, No. 9, pages 1575 - 1581, September 1991.

1988

[1] Josef Hausner, Gerhard R. Olbrich, Peter Russer and Alejandro A. Valenzuela: (doi)
Nonlinear Approach for the Optimization of a DRO at 10.4GHz
18th European Microwave Conference (EuMA), Stockholm, Sweden, pages 268 - 273, September 1988.

1984

[1] Gerhard R. Olbrich, P. Zibis and H.P. Grassl:
Test System for Time Domain Measurements on Elastic SAW-Convolvers
International Symposium on Electromagnetic Compatibility, Tokyo, Japan, pages 793 - 796, October 1984.
[2] Gerhard Olbrich:
Resonanzeffekte in dielektrischen Stützen von Koaxialsteckern
Frequenz, Vol. 38, No. 7-8, pages 166 - 171, July 1984.

1982

[1] Gerhard R. Olbrich and Thomas M. Hartmann: (doi)
Microstrip Sliding Load
Frequenz, Vol. 36, No. 11, pages 295 - 301, November 1982.

1981

[1] Gerhard R. Olbrich:
Ein inhomogenes Bandleitungsmodell zur näherungsweisen Beschreibung des Wellenfeldes der Streifenleitung
Nachrichtentechnische Zeitschrift, Vol. 3, No. 8, pages 197 - 204, 1981.