@inproceedings{RudolphLenkDoerneretal., author = {Rudolph, Matthias and Lenk, Friedrich and D{\"o}rner, Ralf and Heymann, Peter}, title = {Influence of 2 GHz Harmonic Load-Pull on HBT and MESFET Output Power and Efficiency}, series = {1999 IEEE MTT-S International Microwave Symposium digest, June 13 - 19, 1999, Anaheim Convention Center, Anaheim, California}, booktitle = {1999 IEEE MTT-S International Microwave Symposium digest, June 13 - 19, 1999, Anaheim Convention Center, Anaheim, California}, publisher = {Piscataway, NJ}, address = {IEEE}, isbn = {0-7803-5135-5}, pages = {741 -- 744}, language = {en} } @inproceedings{RudolphDoernerHeymannetal., author = {Rudolph, Matthias and D{\"o}rner, Ralf and Heymann, Peter and Lenk, Friedrich}, title = {Modeling of Low-Frequency Noise in GaInP/GaAs Hetero-Bipolar-Transistors}, series = {2001 IEEE MTT-S International Microwave Symposium digest, May 20 - 25, 2001, Phoenix Civic Plaza, Phoenix, AZ, 1967 - 1970, Vol.3}, booktitle = {2001 IEEE MTT-S International Microwave Symposium digest, May 20 - 25, 2001, Phoenix Civic Plaza, Phoenix, AZ, 1967 - 1970, Vol.3}, publisher = {IEEE Service Center}, address = {Piscataway, NJ}, isbn = {0-7803-6538-0}, pages = {1967 -- 1970}, language = {en} } @inproceedings{LenkRudolph, author = {Lenk, Friedrich and Rudolph, Matthias}, title = {New Extraction Algorithm for GaAs-HBTs With Low Intrinsic Base Resistance}, series = {IEEE MTT-S International Microwave Symposium digest, June 2 - 7, 2002, Washington State Convention \& Trade Center, Seattle, Washington, Vol. 2}, booktitle = {IEEE MTT-S International Microwave Symposium digest, June 2 - 7, 2002, Washington State Convention \& Trade Center, Seattle, Washington, Vol. 2}, publisher = {IEEE Service Center}, address = {Piscataway, NJ}, isbn = {0-7803-7239-5}, pages = {725 -- 728}, language = {en} } @inproceedings{RudolphLenkDoerneretal., author = {Rudolph, Matthias and Lenk, Friedrich and D{\"o}rner, Ralf and Heymann, Peter}, title = {Towards a Unified Method to Implement Transit-Time Effects in Pi-Topology HBT CompactModels}, series = {IEEE MTT-S International Microwave Symposium digest, June 2 - 7, 2002, Washington State Convention \& Trade Center, Seattle, Washington, Vol. 2}, booktitle = {IEEE MTT-S International Microwave Symposium digest, June 2 - 7, 2002, Washington State Convention \& Trade Center, Seattle, Washington, Vol. 2}, publisher = {IEEE Service Center}, address = {Piscataway, NJ}, isbn = {0-7803-7239-5}, pages = {997 -- 1000}, language = {en} } @misc{RudolphLenkLlopisetal., author = {Rudolph, Matthias and Lenk, Friedrich and Llopis, O. and Heinrich, Wolfgang}, title = {On the Simulation of Low-Frequency Noise Upconversion in InGaP/GaAs HBTs}, series = {IEEE transactions on microwave theory and techniques}, volume = {54}, journal = {IEEE transactions on microwave theory and techniques}, number = {7}, issn = {0018-9480}, pages = {2954 -- 2961}, language = {en} } @misc{LenkDoernerRumiantsev, author = {Lenk, Friedrich and D{\"o}rner, Ralf and Rumiantsev, Andrej}, title = {Sensitivity Analysis of S-Parameter Measurements Due to Calibration Standards Uncertainty}, series = {IEEE Transactions on Microwave Theory and Techniques}, volume = {61}, journal = {IEEE Transactions on Microwave Theory and Techniques}, number = {10}, issn = {0018-9480}, doi = {10.1109/TMTT.2013.2279774}, pages = {3800 -- 3807}, language = {en} } @misc{LenkSchottHilsenbecketal., author = {Lenk, Friedrich and Schott, Matthias and Hilsenbeck, Jochen and Heinrich, Wolfgang}, title = {A new design approach for low phase-noise reflection-type MMIC oscillators}, series = {IEEE transactions on microwave theory and techniques}, volume = {52}, journal = {IEEE transactions on microwave theory and techniques}, number = {12}, issn = {0018-9480}, doi = {10.1109/TMTT.2004.837319}, pages = {2725 -- 2731}, abstract = {In this paper, optimization of the loaded quality factor QL for reflection-type heterojunction bipolar transistor (HBT) oscillators is investigated. The main result is an optimum relation between the S-parameter phases at the three transistor ports. A new design strategy for this type of oscillator is proposed. The analysis is verified by comparing several Ka-band monolithic-microwave integrated-circuit oscillators in GaAs HBT technology with different resonators. The measured loaded QL values correspond to the measured phase noise of the circuits. At an oscillation frequency of 33 GHz, an excellent phase noise of -87 dBc/Hz at 100-kHz offset frequency is achieved over the whole tuning range.}, language = {en} } @misc{SoniaRichterBrunneretal., author = {Sonia, G. and Richter, E. and Brunner, F. and Denker, A. and Lossy, R. and Mai, M. and Lenk, Friedrich and Bundesmann, J. and Pensl, G. and Schmidt, J. and Zeimer, U. and Wang, L. and Baskar, K. and Weyers, M. and W{\"u}rfl, Joachim and Tr{\"a}nkle, G{\"u}nther}, title = {2 MeV ion irradiation effects on AlGaN/GaN HFET devices}, series = {Solid-State Electronics}, volume = {52}, journal = {Solid-State Electronics}, number = {7}, issn = {0038-1101}, pages = {1011 -- 1017}, abstract = {AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with 2 MeV protons, carbon, oxygen, iron and krypton ions with fluences ranging from 1 × 109 cm-2 to 1 × 1013 cm-2. DC, pulsed I-V characteristics, loadpull and S-parameters of the AlGaN HFET devices were measured before and after irradiation. In parallel, a thick GaN reference layer was also irradiated with the same ions and was characterized by X-ray diffraction, photoluminescence, Hall measurements before and after irradiation. Small changes in the device performance were observed after irradiation with carbon and oxygen at a fluence of 5 × 1010 cm-2. Remarkable changes in device characteristics were seen at a fluence of 1 × 1012 cm-2 for carbon, oxygen, iron and krypton irradiation. Similarly, remarkable changes were also observed in the GaN layer for irradiations with fluence of 1 × 1012 cm-2. The results found on devices and on the GaN layer were compared and correlated.}, language = {en} } @misc{GnanapragasamRichterBrunneretal., author = {Gnanapragasam, S. and Richter, E. and Brunner, F. and Denker, A. and Lossy, R. and Mai, M. and Lenk, Friedrich and Opitz-Coutureau, J. and Pensl, G. and Schmidt, J. and Zeimer, U. and Wang, L. and Krishnan, B. and Weyers, M. and W{\"u}rfl, Joachim and Tr{\"a}nkle, G{\"u}nther}, title = {Irradiation effects on AlGaN HFET devices and GaN layers}, series = {Journal of Materials Science: Materials in Electronics}, volume = {19}, journal = {Journal of Materials Science: Materials in Electronics}, number = {1}, issn = {1573-482X}, doi = {10.1007/s10854-008-9589-1}, pages = {64 -- 67}, abstract = {AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with protons as well as carbon, oxygen, iron and krypton ions of high (68 and 120 MeV) and low (2 MeV) energy with fluences in the range from 1x107 to 1x1013 cm-2. High energy irradiation with protons, carbon and oxygen produced no degradation in devices while krypton irradiation at the fluence of 1x1010 cm-2 resulted in a small reduction of 2\% in the transconductance. Similarly, for GaN samples irradiated with protons, carbon and oxygen at high energy no changes were seen by XRD, PL and Hall effect, while changes in lattice constant and a reduction in PL intensity were observed after irradiation with high energy krypton. Low energy irradiation with carbon and oxygen at a fluence of 5x1010 cm-2 results in small change in the device performance while remarkable changes in device characteristics are seen at a fluence of 1x1012 cm-2 for carbon, oxygen, iron and krypton irradiation. Similarly changes are also observed by XRD, PL and Hall effect for the thick GaN layer irradiated at the fluence of 1x1012 cm-2. The device results and GaN layer properties are strongly correlated.}, language = {en} } @incollection{Lenk, author = {Lenk, Friedrich}, title = {Kapitel "Modulation" und "Multiplex"}, series = {Taschenbuch der Nachrichtentechnik}, booktitle = {Taschenbuch der Nachrichtentechnik}, editor = {Frohberg, Wolfgang}, publisher = {Fachbuchverlag Leipzig im Carl Hanser Verlag}, address = {M{\"u}nchen}, isbn = {3-446-41602-1}, pages = {108 -- 130}, language = {de} }