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Seminarreihe Mikrowellen, Photonik und Kommunikation, SS 2011


Prof. F. Jondral, Prof. T. Zwick, Prof. I. Kallfass, Prof. J. Leuthold, Prof. W. Freude, Prof. C.Koos
Ort: Hörsaal NTI, Geb. 30.10
Zeit: Donnerstag, 14:00 Uhr
Für Seminar-Vorschläge kontaktieren Sie bitte: Angelika Olbrich


21.04.2011 'Neue Entwicklungen zu LTE Advanced'
Dr.-Ing. Thomas Haustein, Fraunhofer Heinrich-Hertz-Institut Berlin
28.04.2011 'Challenges in next generation optical communication systems - an industrial perspective'
Dr. Stefan Spaelter, Siemens München

12.05.2011 'Technologies for optical transmission beyond 100 Gb/s'
Dr. Fred Buchali, Alcatel-Lucent, Stuttgart
19.05.2011 'Galliumnitrid für die Elektronik
Prof. Dr. Oliver Ambacher, Fraunhofer-Institut für Angewandte Festkörperphysik IAF, Freiburg
26.05.2011 'Analog-Digital- und Digital-Analogwandler mit höchsten Wandlerraten'
Prof. Berroth, Universität Stuttgart

Die ungebrochene Nachfrage an steigende Datenraten erfordert bei drahtlosen wie bei drahtgebundenen oder faseroptischen Übertragungsstrecken neue Systeme mit komplexe Modulationsverfahren bei hoher spektraler Effizienz. Ein Lösungsansatz zur Erzeugung und Detektion breitbandiger Hochfrequenzsignale sind Analog-Digital- und Digtal-Analogwandler mit Wandlerraten größer 25 GS/s, die für 100 Gb/s Übertragungssysteme entwickelt wurden. In dem Vortrag werden die Prinzipien dieser Wandler mit höchsten Abtastraten in CMOS-Technologie erläutert und mögliche Anwendungsszenarien vorgestellt.
02.06.2011 kein Vortrag, Feiertag (Chr. Himmelfahrt)
09.06.2011 'Introduction to nonlinear and tunable metamaterials'
Dr. Mikhail Lapine, Australian National University, Canberra
16.06.2011 'Network Utility Maximization in Wireless Communication Systems'
Prof. Dr.-Ing. Wolfgang Utschick, TU München

A special class of wireless single hop networks is considered, where the data rates of multiple users, element of certain quality of service classes, are selected from a set of achievable physical layer rates such that performance, measured by a network wide utility, is maximized. The problem as such is well researched and multiple algorithmic methods to compute solutions, typically methods working on the dual formulation of the problem are available. In this work, we first recapitulate the most prominent algorithmic methods and afterwards introduce an alternative method. We investigate primal and dual implementations of the algorithm and apply it to reference scenarios, including a multi-cell network with interference coordination. Numerical simulations indicate a drastic reduction in iterations needed to compute a solution by the novel algorithm compared to state of the art methods.
23.06.2011 kein Vortrag, Feiertag (Fronleichnam)
30.06.2011 'Planare Antennen und Antenna-in-Package Konzept für Kommunikations- und Radarsysteme bei 60 GHz und 77 GHz'
Prof. Dr. Martin Schneider
Universität Bremen - TZI, RF & Microwave Engineering Laboratory
07.07.2011 'Analysis & Compensation of Phase Variations in Variable Gain Amplifiers for Adaptive Antenna Beamforming Systems'
Prof. Dr.-Ing. habil. MBA Frank Ellinger, Head of Chair for Circuit Design and Network Theory,
University of Technology, Dresden

The tradeoff between coverage range, reliability, data speed and power consumption can be improved in wireless systems by means of adaptive antenna combining. By smart weighting of the phases and amplitudes of multiple antenna signals, the antenna gain can be increased and intersymbol interferences can be reduced. Most systems perform the vector weighting of the antenna signals in the baseband. Since multiple circuit paths are required from RF to baseband, the resulting power consumption and costs are very high. These drawbacks can be mitigated by performing the adaptive combining in the RF front-end. In this case, only one path from IF to baseband is required. To reduce the control complexity, the phase shifters should vary the phase without manipulating the gain, and the gain control components should adjust the gain without changing the phase. However, if we e.g. vary the transconductance or the load resistance in amplifiers for gain control, the RC time constants of the transistors change leading to significant undesired phase variations. The focus of this talk is on corresponding compensation techniques. The transmission phase variations versus gain in common emitter and common base amplifiers are analyzed revealing that these stages can be tuned to yield opposite phase characteristics versus gain. By cascading these two stages, e.g. on basis of a cascode, and optimizing added feedback elements, it is possible to compensate these phase variations. A universal circuit analysis based on bipolar transistors is derived. The analysis is verified by implementation of a C-Band low noise cascode amplifier in 0.25 mm silicon germanium (SiGe) hetero bipolar transistors (HBTs). The transmission phase variations are reduced to 3° and 6°, respectively, which is around a factor of 7 better than for a conventional non-compensated cascode topology. The insights can also be mapped to other transistors such as field effect transistors (FETs).
14.07.2011 'A SiGe analog receiver frontend for ultra-high-rate, short-range 60 GHz communication systems'
Prof. Dr.-Ing. Hermann Schumacher
Universität Ulm, Institut für elektronische Bauelemente und Schaltungen

The availability of unlicensed operation in the 57-64 GHz range has opened up a rapidly developing market for short range, high speed data links. For multi-GBit/s transmission speeds, the cost and power consumption of a high resolution, high rate analog-to-digital converter is frequently a bottleneck. We report on an alternative method, fully analog demodulation of BPSK and QPSK signals, for symbol rates up to 5.5 GS/s. The receiver has been implemented in monolithic form in a low-cost SiGe HBT technology.

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