Die Anwendung des Homodyn-Prinzips zur Netzwerkanalyse im Millimeter-Wellen-Bereich

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Hybrid antenna design for an optically powered SHF RFID transponder applicable in metals

This paper presents a hybrid antenna design for an optically powered super high frequency (SHF) radio frequency identification transponder applicable for the integration into metal. The key feature of the antenna is its ability to receive microwave signals at SHF for data communication and optical signals for the power supply of the transponder. The antenna design is based on a circular waveguide which is filled with a bundle of polymer optical fibers to guide light to the photodiodes. In addition, a transition is placed within the circular waveguide to transfer the waveguide mode of the SHF signal into a microstrip mode which is a more suitable structure for the integration of electronic transponder components. This paper discusses the constraints and solutions for the aforementioned combination of SHF microwave and light. The figures of merit of the optical power supply are presented, including considerations of the light distribution and the obtained power as a function of the incident angle and the used polymer optical fiber diameter. Furthermore, the measured gain and return loss of the SHF antenna structure is compared to the simulated results. © Cambridge University Press and the European Microwave Association, 2013

Signatures of electronic polarons in La1−x_{1-x}Sr1+x_{1+x}MnO4_4 observed by electron energy-loss spectroscopy

The dielectric properties of La$_{1-x}$Sr$_{1+x}$MnO$_4$ single crystals with x = 0, 0.125, 0.25, and 0.5 were studied by means of electron energy-loss spectroscopy as a function of temperature and momentum transfer. A clear signature of the doped holes is observed around 1.65 eV energy loss, where spectral weight emerges with increasing x. For all $x \neq 0$, this doping-induced excitation can propagate within the ab-plane, as revealed by a clear upward dispersion of the corresponding loss peak with increasing momentum transfer. The hole-induced excitation also shifts to higher energies with the onset of magnetic correlations for x = 0.5, implying a strong coupling of charge and spin dynamics. We conclude that (i) the loss feature at 1.65 eV is a signature of electronic polarons, which are created around doped holes, and that (ii) this low-energy excitation involves the charge transfer between manganese and oxygen. The finite dispersion of these excitations further indicates significant polaron-polaron interactions.Comment: 7 pages, 4 figure

Messverfahren zur Bestimmung der EMV-relevanten Störanteile in Hochvolt-Bordnetzen von Kraftfahrzeugen

In Hybrid- oder Elektrokraftfahrzeugen stellt der Aspekt der elektromagnetischen Verträglichkeit (EMV) des Hochvolt-(HV)-Netzwerks eine besondere Herausforderung dar [Hohloch, J. ; Köhler, W. ; Tenbohlen, S. ; Aidam, M. ; Krauß, T.: Charakterisierung und Vergleich leitungsgebundener Störungen an KFZ-Hochvoltbordnetzen. In: EMV 2012, Internationale Fachmesse und Kongress für Elektromagnetische Verträglichkeit. Düsseldorf, 2012]. Hohe übertragene Leistungen und steile Taktflanken lassen die HV-Leitungen zu Quellen hochfrequenter Störemission werden. Um diese Effekte besser erschließen zu können, ist es notwendig, die Vorgänge im Inneren des geschirmten HV-Systems zu erfassen. Dies kann durch eine breitbandige Messung der zeitaufgelösten Ströme und Spannungen direkt auf den HV-Leitungen erreicht werden. Die derzeitigen Lösungen für diese Messungen (Spannungsteiler, Rogowskispule, Stromzange, Shunt-Widerstand und Hallsensor) haben jedoch den Nachteil, dass dadurch insbesondere die EMV-relevanten hochfrequenten Störanteile der zu vermessenden Systemkomponenten nicht erfasst oder zumindest deutlich beeinflusst werden. Daher stellt dieser Beitrag ein neu entwickeltes Messverfahren vor, das diese Nachteile nicht aufweist. In Kapitel 2 werden Kalibrierung und Messung im Detail vorgestellt und verifiziert. In Kapitel 3 wird der Messaufbau zum Einsatz in Elektrofahrzeugen dargestellt. Weiterhin wird die Bedeutung der Rückwirkungsfreiheit des entwickelten Verfahrens hervorgehoben, bevor erste Messungen an einem Fahrzeug durchgeführt werden

Determining the Short-Range Spin Correlations in Cuprate Chain Materials with Resonant Inelastic X-ray Scattering

We report a high-resolution resonant inelastic soft x-ray scattering study of the quantum magnetic spin-chain materials Li2CuO2 and CuGeO3. By tuning the incoming photon energy to the oxygen K-edge, a strong excitation around 3.5 eV energy loss is clearly resolved for both materials. Comparing the experimental data to many-body calculations, we identify this excitation as a Zhang-Rice singlet exciton on neighboring CuO4-plaquettes. We demonstrate that the strong temperature dependence of the inelastic scattering related to this high-energy exciton enables to probe short-range spin correlations on the 1 meV scale with outstanding sensitivity.Comment: 5 pages, 4 figure

24 GHz RFID Communication System for Product Lifecycle Applications

This paper presents the fundamental construction of a 24 GHz Radio Frequency Identification system using an optically powered transponder integrable in metal. Hereby, the system consists of a reader and a transponder. An overview of the transponder design including the modulator and demodulator circuit and its main characteristic values is given. On transponder side the communication is controlled by a low-power microcontroller. An I2C bus is implemented allowing a flexible connection of sensors and memory. Furthermore, the reader concept is presented and a communication example is used to explain the implemented protocol