Search results for: R. Weigel
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Forest Ecology and Management > 2018 > 428 > C > 66-80
Despite their long history as a forest dominant, the importance of Quercus (oak) species is declining under contemporary disturbance regimes in many parts of the world. This is cause for concern considering the great economic and ecological value of this genus. While many chronosequence studies have shown that clearcutting has accelerated the loss of Quercus species in forests of eastern North America,...
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For monolithically integrated vector network analyzers (VNA) a broadband multi-octave receiver is shown, which exhibit a very wide frequency range from 1–32 GHz. It consists out of a low noise amplifier (LNA) and an active mixer, followed by an output buffer. With the presented design, a maximum achievable conversion gain (CG) of 16.6 dBm can be reached. The main design-goal is a very flat deviation...
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This paper presents the design of a linearly polarized electronically reconfigurable transmitarray in K-band for beam steering applications. The transmitarray is a linear arrangement of five unit cells. Each unit cell provides a continuous phase tuning range of 360° which has been confirmed with numerical and experimental results. The unit cells are formed of multiple single layers of RF-laminate...
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In the present work, nonlinearities in temperature compensating (TC) SAW devices are investigated. The materials used are LiNbO3-rot128YX as the substrate and Copper electrodes covered with a SiO2-layer as the compensating layer. In order to understand the role of these materials for the nonlinearities in such acoustic devices, a FEM simulation model in combination with a perturbation approach [1]...
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This paper presents a 15-bit digital power amplifier (DPA) with 1.6W saturated output power. The topology of the polar switched-current DPA is discussed together with the architecture of the output transformer which is implemented in BEOL as well as in WLCSP metal layers. The chip is fabricated in a standard 28nm CMOS process and exhibits an EVM of 3.6%, E-UTRA ACLR of 34.1dB, output noise of −145...
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Interferences injected to an RF circuit may strongly deteriorate the electrical performance. Parasitic coupling via substrate is one of the dominant interference transmission mechanisms in highly integrated systems. The effect of substrate coupling becomes more critical at higher circuit frequencies. This poses a particular challenge for highly integrated millimeter-wave systems, since isolation techniques...
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To fully realize the advantages of DC microgrids, such as high energy efficiency, excellent reliability, and the ability to handle high-dynamic loads, special DC measurement equipment for control, safety and monitoring tasks are required. The equipment must be energy efficient, precise, and should combine a high bandwidth with fast digital communication. To fulfill all the special needs of DC microgrids,...
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A multirate, fractional-N RF digital phase-locked loop (DPLL) phase modulator implementation for polar transmitter supporting cellular communication standards up to 4G LTE-A is demonstrated for the first time. The RF-DPLL integrates LC-tank-based digital-controlled oscillator (DCO) cores with ΔΣ-noise shaping and fractional sample rate conversion to account for a broad range of frequency bands and...
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In this paper, a functional principle for a broadband thermal detector suited for a monolithical integration is shown. Two tantalum load resistors are heated by an input signal, while the temperature at a fixed distance is recorded on chip with a differential temperature sensing bridge. An integrated differential to single-ended stage amplifies the bridges differential voltage and provides an output...
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At high frequency, Bulk Acoustic Wave (BAW) devices are mainly used for filtering in front-ends of modern mobile transceivers. Furthermore, the transmitter filters are usually used at high input power levels of up to 33 dBm, which lead to nonlinearity and self-heating within the filter. In this work a thermo-electro-mechanical Mason model combined with a 3-dimensional electromagnetic finite element...
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In this work, the thermal effects of a tunable matching network (TMN) based on micro electro mechanical systems (MEMS) are investigated. A reconfigurable power amplifier (PA) is proposed based on a TMN. The thermal effects are modeled and their influence on the linearity of the PA are addressed. The study is aided by a behavioral model of the capacitive MEMS switch which has been extended in order...
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2016 46th European Microwave Conference (EuMC) > 1299 - 1302
An integrated antenna diversity system is described which enables a high increase of reception performance for satellite digital audio radio services (SDARS). A detailed analysis is given for the gain and noise figure requirements specifically regarding the implementation in an integrated circuit. On base of this analysis a hardware demonstrator of the scan-phase antenna diversity system is realized...
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2016 IEEE SENSORS > 1 - 3
This paper analyses a novel production technique for the fabrication of microelectromechanical system (MEMS) with a gap in the scale of nanometer. The technology is based on a density-changing layer, which let a gap arise through the shrinkage of this layer. After the description of the technology, the requirements for monolithic integration and CMOS compatibility with respect to this technology are...
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2016 IEEE SENSORS > 1 - 3
This paper describes a low-cost measurement system based on two crossed laser barriers to measure the angle, the position as well as the velocity of an object with known shape, which is passing the measurement system. Due to the simple system setup this leads to a low-cost vectorial speed measurement system, which is capable of high speed measurements. Furthermore, as a demonstrator, a table soccer...
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In this work, the Poly-Harmonic Distortion (PHD) model has been used to characterize the nonlinearities of Bulk Acoustic Wave (BAW) solidly mounted resonators (SMR). The new approach of using X-parameters for characterization and simulation of nonlinearities is described. The amplitude and phase of the fundamental mode and its harmonics up to third order have been measured and simulated by using the...
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In this work, the impact of the intrinsic nonlinear effects of bulk acoustic wave (BAW) filters on the demodulation performance of an LTE user equipment (UE) receiver at 2600 MHz is evaluated. The nonlinear effects that shape the generation of higher harmonics in the BAW resonator are covered in a nonlinear model implemented in Keysight's advance design system (ADS) and validated through nonlinear...
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This work presents an intelligent analog image sensor system for smart camera applications with the need of edge or marker detection. The system consists of a 3×3 read-out CMOS image sensor, an analog Sobel stage and additional circuitry like operational amplifiers and comparators to compute a 1 bit image with the edges present in the taken photo. This information can then be further processed digitally...
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Tropical Medicine & International Health > 21 > 6 > 792 - 798
ObjectivesPostgraduate courses can contribute to better‐qualified personnel in resource‐limited settings. We aimed to identify how entry characteristics of applicants predict performance in order to provide support measures early.
MethodsWe describe demographic data and end‐of‐module examination marks of medical doctors who enrolled in a first semester module of two one‐year MSc programmes between...
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Electronics Letters > 2016 > 52 > 11 > 921 - 923
It is shown that precise output voltage clamping levels can be achieved under any operating condition by clamping the input of operational transconductance amplifier to a process insensitive reference and multiplexing the levels based on comparator decision. This circuit was implemented in a 40 V bipolar CMOS process. The fabricated circuit clamps the output voltage at 5.4 V with a precision of ±100...
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In this paper a novel 61GHz radar sensor node for industrial positioning and distance measurement is presented. The sensor provides numerous functions enabling a broad range of signal processing technologies and is designed with regard to cost-efficient implementation only using commercial available components without limiting the area of possible applications. Beside the requirement analysis and...
