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The underlying paper and investigations deal with the main functionality and physical parameters of contactless smartcard and NFC (Near Field Communication) devices. The specific need of impedance matching for reader devices is pointed out in particular, as the correct matching represents a major performance indicator of the system. Therefore, in a first step, the dedicated parameters are analyzed for a reader device. Based on these insights, detailed analysis of the concept, the implementation and the verification of an automatic impedance matching circuit for NFC antennas with a frequency of 13.56 MHz is given. Besides an introduction to manual tuning and its issues, the fundamental components of an automatic tuning system are outlined. A lab-scaled prototype is built and demonstrated. Finally, the successful operation of this system is tested with several different antennas. Furthermore, the effects of detuning due to dynamic behavior are pointed out, characterizing the need for further investigations.Das vorliegende Paper fasst die grundlegenden Funktionen und physikalischen Parameter f€ u ur kontaktlose Smartcards und NFC (Near Field Communication)-Einheiten zusammen. Die Notwendigkeit der Impedanzanpassung des Leseger€ a ats wird gezeigt, da die Anpassung ein wesentlicher Parameter f€ u ur die Effizienz des Systems ist. Aus diesem Grund wird im ersten Schritt eine Analyse der grundlegenden Leseger€ a atsparameter durchgef€ u uhrt. Basierend auf diesen Erkenntnissen und Ergebnissen werden ein detailliertes Konzept und eine m€ o ogliche Implementierung einer automatischen Impedanzanpassung f€ u ur NFC-Antennen bei einer Frequenz von 13,56 MHz vorgestellt. Neben dem manuellen Anpassen der Impedanz und den damit verbundenen Problemen werden die ben€ o otigten Komponenten f€ u ur eine automatische Impedanzanpassung vorgestellt. Ein laborgerechter Prototyp wird aufgebaut und die erfolgreiche Arbeitsweise des Systems getestet und an verschiedenen Antennen gezeigt. Schlussendlich werden die Auswirkungen des Detunings basierend auf dynamischen Effekten dargestellt und die Notwendigkeit weiterer Entwicklungen gezeigt.Schl€ u usselw€ o orter: automatische Impedanzanpassung; kontaktlose Smartcards; Impedanzanpassung; NFC

A blower-type wind tunnel for physiological bird flight experiments has been developed, constructed and evaluated. Since the birds to be investigated are rather big (Northern Bald Ibis, Geronticus eremita), the cross-sectional area of the test section measures 2.5 m × 1.5 m. The maximum achievable flow speed is approximately 16 ms−1. The wind tunnel exhibits a flexible outlet nozzle to provide up- and downdraft to allow for gliding and climbing flights. The current paper describes in detail the layout, design and construction of the wind tunnel including its control. Numerical simulations of the flow and measurements of the velocity distribution in the test section are presented. Apart from a non-homogeneous flow region in the mixing layer at the boundaries of the free jet, the test section exhibits a very even velocity distribution; the local speed deviates by less than two percent from the mean velocity. The turbulence intensity inside the test section was measured to be between 1 and 2%. As a constraint, a limited budget was available for the project. Four northern bald ibises were hand-raised and trained to fly in the wind tunnel.

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