SiGe VCOs operating up to 88 GHz, suitable for automotive radar sensors

VCOs fully integrated in an SiGe preproduction technology are presented. By cutting interconnection lines a wide frequency range can be covered, up to 88.4 GHz. Special effort has been made to meet the demands for 77 GHz automotive radar. In the corresponding tuning range from 75.3 to 79.6 GHz, an output power of about 11 dBm (with -2.2 dBm potential measurement uncertainty) was achieved for each of the two complementary outputs, i.e. in total 14 dBm. The phase noise is about -94 dBc/Hz at 1 MHz offset frequency.     

Monolithic integration of a 5.3 GHz regenerative frequency divider using a standard bipolar technology

A monolithic microwave frequency divider IC with an operating range of 1.4?5.3 GHz was developed and fabricated in a standard bipolar technology. The circuit operates on the principle of `regenerative frequency division?. Compared to the most popular divider concepts based on a master-slave D-flip-flop, an almost twice as high input frequency can be divided, provided that the same technology is used. A further advantage is the low power consumption.     

Locked discrete event systems: How to model and how to unlock

To model qualitative aspects of discrete event systems, i.e., the order of the events is of sole importance, we use a triple consisting of the set of all possible events (the alphabet), the set of all behavior (possible strings of events), and the set of all tasks (completed behavior). We use this view to model synchronous as well as asynchronous connection of systems. Moreover, it is easy to define notions like deadlock and livelock in this view. We give a method to construct a second system that, in connection with the original system, gets rid of its deadlock and/or livelock. A state-space representation is introduced. In this representation computations can be done effectively.     

13 Gb/s Si-bipolar AGC amplifier IC with high gain and wide dynamicrange for optical-fiber receivers

A complete linear automatic-gain-control (AGC) amplifier for a 10 Gb/s optical-fiber link was integrated on a single chip, using a Si-bipolar production technology with f_T≈22 GHz. It is characterized by a high gain of 37 dB, linear operation over a wide input dynamic range of 47 dB, a maximum data rate of 13 Gb/s, and a gain-independent 3-dB cut off frequency of 10 GHz. The circuit consumes 850 mW at a single supply voltage of -6.5 V. It can be operated in both a single-ended and differential mode. A novel 50-Ω input matching circuit with only small return loss is used. Two separate output buffers with a constant output voltage swing of 500 mV_p-p allow splitting up the output signal without use of external components     

Wide-band symmetrical analog multiplier IC for coherentoptical-fiber receivers operating up to 10 Gb/s

A versatile analog four-quadrant multiplier IC with large bandwidth (DC to 6 GHz and 10 Gb/s) and large dynamic range is presented. It was mainly developed for differential-phase-shift-keying (DPSK) phase demodulator and polarization diversity receivers in coherent optical-fiber transmission systems. The circuit consumes 450 mW and only needs a single power supply of -5 V. The circuit principle used allows exact symmetry with respect to both linear inputs, which reduced multiplication errors. In the intended application, especially, the time jitter and the offset voltage of the output pulse patterns are reduced to negligible values. The IC was realized in a 1.25-μm double-polysilicon bipolar technology     

Time-optimal control of linear systems

A useful procedure for the solution of time-optimal control problems for linear systems is presented. The procedure consists of a direct search method for the determination of the best diagonal weighting matrix used in a Liapunov function for the system. The control policy chosen to minimize the forward difference of the Liapunov function yields very rapid approach to the origin. Numerical results are presented for a linear six-plate gas absorber to show the feasibility of the proposed method. Even in the presence of disturbances the system can be taken to and kept at the vicinity of the origin.     

Harnessing the Melting Peculiarities of Ultra‐High Molecular Weight Polyethylene Fibers for the Processing of Compacted Fiber Composites

Summary: Compacted fiber composites offer unique properties due to their lack of an extraneous matrix. The conditions of processing ultra‐high molecular weight polyethylene (UHMWPE) fibers were simulated in a heated pressure cell. In situ X‐ray diffraction measurements were used to follow the relevant transitions and the changes in the degree of crystallinity during melting and crystallization. The results strongly support the suggestion that the hexagonal crystal phase, in which the chain conformation is extremely mobile on the segmental level, constitutes the physical basis of compaction technologies for processing UHMWPE fibers into a single‐polymer composite. This report suggests that using a pseudo‐phase diagram outlining the occurrence of different phases during slow heating and the degree of crystallinity can provide valuable insight into the technological parameters relevant for optimal processing conditions.

Degree of crystallinity as a function of pressure and temperature in a region relevant to compaction processes.     

Correlation of reactivity and electrical resistivity of coke

A correlation between the reactivity and electrical resistivity of a series of cokes was determined using cokes prepared from blends of medium- and high-volatile coals. After correcting for the ash yield of the coke and the density of the resistivity specimen, a statistically significant relation between reactivity and resistivity was established. As the resistivity test requires much less time to perform than the reactivity test, it can be considered as an alternative approach to reactivity testing currently performed for quality control purposes.     

Mathematical Modeling and Simulation of Ozonation Processes in a Downstream Static Mixer with Sieve Plates

New standards for drinking water disinfection require better optimization of the ozonation stage on the basis of the concentration×contact time (CT) concept, and production of ozone from pure oxygen at higher concentrations presumes application of the new type of contactors operating efficiently at lower gas/liquid volumetric ratios. One possible construction to meet these requirements is a downstream static mixer with sieve plates. At higher flow rates of liquid in this mixer, the interfacial area may reach 10,000m²/m³ at energy dissipation 1–5kW/m³. Due to the very intensive hydrodynamic regime the ozone utilization degree in the gas phase reaches 98–100% in natural lake water ozonation. Mathematical simulation of lake water ozonation in this mixer indicated that the process proceeds mostly in the diffusion or kinetic regime depending on the operating parameters. The dominating parameters besides the sieve geometry are the liquid flow rate in the holes of the sieves and the volumetric liquid/gas ratio.     

The effect of damming on biological quality according to macroinvertebrates in some Estonian streams,Central—Baltic Europe: A pilot study

The effect of damming on the structure of the macroinvertebrate community and biological quality was studied in nine (the 3–6th order) lowland streams of Estonia, Central—Baltic ecoregion of Europe. Four habitats—reservoirs with accumulated fine sediments, reservoirs with hard bottom, and two corresponding below‐dam areas (both fast‐flowing)—were compared to study whether and how significantly the bottom substrata in dammed areas affected macroinvertebrates and biological quality downstream of dams. The standard kick‐net samples (1.25 m², complemented with qualitative sample) were collected in autumn 2005—spring 2006. The multimetric biological quality, based on five macroinvertebrate indices (total taxa richness, EPT taxa richness, Average Score Per Taxon, Danish Stream Fauna Index, Shannon diversity) was estimated and compared with reference values. Biological quality in reservoirs with hard bottom and their downstream reaches corresponded to good, or even high quality. Conversely, damming affected biological quality significantly and negatively, above the dam if fine sediments were accumulated. The effect was the strongest within muddy reservoirs themselves (revealing moderate quality only). However, some harmful consequences of mud were observed also downstream of dams. The results also demonstrated that the indices of estimation of organic pollution and/or general quality were able to reflect significant changes in stream flow. Copyright © 2010 John Wiley & Sons, Ltd.