Bulk acoustic wave‐coupled resonator filters: Concept,design, and application

Bulk‐acoustic‐wave‐coupled resonator filters is an emerging technology that is capable of meeting increasingly ambitious demands of wireless applications by addressing performance, chip size, and die cost. This article outlines the fundamental design principles of these filters. A major consideration of filter design is the choice of the coupling structure between the two vertically stacked resonators. This can be either a multilayer Bragg coupler or a novel structure using a single layer of a very low acoustic impedance material. It is demonstrated how spurious modes are related to the dispersion diagram and how they affect the passband characteristics. For the suppression of these spurious modes suitable edge termination techniques are discussed. Based on optimized coupler performance and known parasitic effects, we analyze circuit design methods for microwave filters and duplexers with specific passband, roll‐off, and wideband responses. We show as example a miniature 2.0 × 1.6 mm² Universal Mobile Telecommunication System (UMTS) Band1 duplexer fabricated using the coupler resonator technology. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Metrics for weighted transition systems: Axiomatization and complexity

Simulation distances are essentially approximations of simulation which provide a measure of the extent by which behaviors in systems are inequivalent. In this paper, we consider the general quantitative model of weighted transition systems, where transitions are labeled with elements of a finite metric space. We study the so-called point-wise and accumulating simulation distances which provide extensions to the well-known Boolean notion of simulation on labeled transition systems.We introduce weighted process algebras for finite and regular behavior and offer sound and (approximate) complete inference systems for the proposed simulation distances. We also settle the algorithmic complexity of computing the simulation distances.     

Micro-spherically textured organic light emitting diodes: A simple way towards highly increased light extraction

We demonstrate a method to increase the efficiency of white organic light emitting diodes (WOLEDs) by a factor of up to 3.7. By fabricating the WOLED on top of a monolayer of SiO₂-microspheres we texture the WOLEDs spherically. We attribute the significant increase of the device efficiency to a larger area on the same footprint and to an enhanced outcoupling of waveguide and substrate modes. Measurements reveal that the I–V characteristic of the device as well as the emissive characteristic remains unchanged.     

Molybdenum oxide anode buffer layers for solution processed,blue phosphorescent small molecule organic light emitting diodes

In this work we present solution processed organic light emitting diodes (OLEDs) comprising small molecule, blue phosphorescent emitter layers from bis(4,6-difluorophenylpyridinato-N,C2)picolinatoiridium doped 4,4′,4″-tris(carbazol-9-yl)-triphenylamine and molybdenum trioxide (MoO₃) anode buffer layers. The latter were applied from a molybdenium(V)ethoxide precursor solution that was thermally converted to MoO₃ at moderate temperatures. The high work function MoO₃ facilitated hole injection into the emission layer. The MoO₃ layer properties were investigated by means of energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy and Kelvin probe force microscopy. MoO₃ buffer layers performed superior to the commonly used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and enabled an enhanced OLED device efficiency.     

Organic Semiconductors for Thermoelectric Applications

The thermoelectric performance of thin films fabricated from two commercially available, highly conductive polymer formulations based on poly (3,4-ethylendioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was investigated. In order to enhance the electrical conductivity, the high-boiling solvent dimethyl sulfoxide (DMSO) was added. By changing the content of DMSO the electrical conductivity was increased by a factor of two without changing the Seebeck coefficient or the thermal conductivity. We achieved ZT = 9.2 × 10⁻³ at room temperature upon the addition of 5 vol.% DMSO to the PEDOT:PSS formulation.     

Vakuumtechnologie für die chemische Verfahrenstechnik

Vacuum technology for the chemical industry process engineering – New developments – established principles Vacuum technology in chemical process engineering has evolved constantly over the past decades. In the beginning, liquid ring vacuum pumps were used in almost all chemical processes. But this all changed in the 1960s with the introduction of the once-through oil-lubricated rotary vane vacuum pump. The development of the dry screw vacuum pump in the 1990s represented another milestone. These are the three main types of technology available to chemical engineers today. They therefore have the choice between the traditional but proven technology of the liquid ring vacuum pump, the once-through oil-lubricated rotary vane vacuum pump and the modern screw vacuum pump that requires no operating fluids whatsoever. The decision as to which type is the right choice should be left to a proven vacuum specialist. Each and every critical parameter – from the process conditions, process gases and integration into process control right through to assessing the economic efficiency, safety and reliability of the future vacuum generation – must be taken into consideration.