A 1-V 10.7-MHz switched-opamp bandpass /spl Sigma//spl Delta/ modulator using double-sampling finite-gain-compensation technique

A 1 V switched-capacitor (SC) bandpass sigma-delta (/spl Sigma//spl Delta/) modulator is realized using a high-speed switched-opamp (SO) technique with a sampling frequency of up to 50 MHz, which is improved ten times more than prior 1 V SO designs and comparable to the performance of the state-of-the-art SC circuits that operate at much higher supply voltages. On the system level, a fast-settling double-sampling SC biquadratic filter architecture is proposed to achieve high-speed operation. A low-voltage double-sampling finite-gain-compensation technique is employed to realize a high-resolution /spl Sigma//spl Delta/ modulator using only low-DC-gain opamps to maximize the speed and to reduce power dissipation. On the circuit level, a fast-switching methodology is proposed for the design of the switchable opamps to achieve a switching frequency up to 50 MHz. Implemented in a 0.35-/spl mu/m CMOS process (V/sub TP/=0.82 V and V/sub TN/=0.65 V) and at 1 V supply, the modulator achieves a measured peak signal-to-noise-and-distortion ratio (SNDR) of 42.3 dB at 10.7 MHz with a signal bandwidth of 200 kHz, while dissipating 12 mW and occupying a chip area of 1.3 mm/sup 2/.     

Crosstalk between microstrip transmission lines

Methods for prediction of crosstalk between microstrip transmission lines are reviewed and simplified for the weak-coupling case. Classical coupled transmission line theory is used for uniform lines, and potential and induced EMF methods are used for crosstalk between nonuniform lines. It is shown that the potential method is equivalent to classical coupled transmission line theory for the case of uniform lines. An experiment was performed for uniform coupled microstrip lines for frequencies from 50 MHz to 5 GHz, and good agreement between theory and measurement was obtained for both near- and far-end crosstalk     

High-frequency analysis of the Ellipticus antenna

Efficient numerical solution techniques have been developed and used to examine the electromagnetic fields that can be developed in the working volume of the CW Ellipticus antenna operated at frequencies from 100 kHz to 1 GHz. An exponentially tapered transition section is designed to obtain the desired illumination pattern in the working volume. The input transition section is needed for impedance matching and to drive efficiently the Ellipticus antenna. A parametric study is performed to ascertain the performance of the Ellipticus antenna for frequencies up to 1 GHz     

Long multifilament Bi-2223 Ag-sheathed superconducting tapes and solenoids

Multifilament Ag-sheathed BiPbSrCaCuO (2223) superconducting tapes containing 49 filaments were fabricated by the powder-in-tube route and the roll-anneal process. The transport critical current densityJ _c was 1.3×10⁴ A cm^–2 at 77 K and 7×10⁴ A cm^–2 at 4.2 K in self-field. A 12-m-long tape was used to construct superconducting solenoids (50, 28, and 14 mm internal diameters) generating dc fields 380–1070 G at 4.2 K. Measurements of the variation ofJ _c with field (0–1.6 T) and bend strain (0–5%) are used to explain the performance of the solenoids. The critical bend strain of tapes was about 1.5%.     

Self-monitoring and intake interviewers' therapeutic orientations.

A therapist's theoretical orientation is likely to influence every facet of the therapeutic process. We explore the relationship of therapeutic orientation and self-monitoring style. To test the hypothesis that high self-monitors would be more eclectic than low self-monitors, we surveyed 30 intake therapists at a child guidance center. Results supported the hypothesis; those frequently using more than one orientation had higher self-monitoring scores. Furthermore, self-monitoring correlated negatively with psychoanalytic endorsement, but in a positive direction with behavioral, systems and eclectic endorsements. Results are discussed in terms of training needs of those differing in self-monitoring style. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scattering and absorption by thin metal wires in rectangularwaveguide-FDTD simulation and physical experiments

The high-frequency internal impedance model of a round ohmic conductor is incorporated into the subcell thin-wire formulation of the finite-difference time-domain method to model the microwave properties of metal wires. For magnetic metals, such as steel, an effective conductivity is introduced to account for the increase in ohmic loss due to the high-frequency permeability. Physical experiments with half-wave resonant copper- and steel-wire inclusions, supported by a dielectric slab in a standard S-band rectangular waveguide, support the formulation     

An efficient optimistic message logging scheme for recoverable mobile computing systems

A number of checkpointing and message logging algorithms have been proposed to support fault tolerance of mobile computing systems. However, little attention has been paid to the optimistic message logging scheme. Optimistic logging has a lower failure-free operation cost compared to other logging schemes. It also has a lower failure recovery cost compared to the checkpointing schemes. This paper presents an efficient scheme to implement optimistic logging for the mobile computing environment. In the proposed scheme, the task of logging is assigned to the mobile support station so that volatile logging can be utilized. In addition, to reduce the message overhead, the mobile support station takes care of dependency tracking and the potential dependency between mobile hosts is inferred from the dependency between mobile support stations. The performance of the proposed scheme is evaluated by an extensive simulation study. The results show that the proposed scheme requires a small failure-free overhead and the cost of unnecessary rollback caused by the imprecise dependency is adjustable by properly selecting the logging frequency.     

Novel level-identifying circuit for flash multilevel memories

This paper presents a high-speed, small-area circuit specifically designed to identify the levels in the read out operation of a flash multilevel memory. The circuit is based on the analog computation of the Euclidean distance between the current read out from a memory cell and the reference currents that represent the different logic levels. An experimental version of the circuit has been integrated in a standard double-metal 0.7-μm CMOS process with a die area of only 140×100 μm². Operating under a 5-V power supply, this circuit identifies the read-out current of a memory cell, and associates it with the appropriate logic level in 9 ns     

High performance of silicided silicon-sidewall source and drain (S4D) structure

A silicided silicon-sidewall source and drain (S⁴D) structure is proposed for sub-0.1-μm devices. The merit of the S⁴D structure is that the series resistance of the source and drain is significantly reduced since the silicide layer is attached very close to the gate electrode and the silicon sidewall can be doped very highly. Thus, very high drain current drive can be expected, Another advantage of this structure is that the source and drain extensions are produced by the solid-phase diffusion of boron from the highly doped silicon-sidewall. Thus, shallow extensions with very high doping can be realized. A 75-nm gate length pMOSFET fabricated with this structure is shown to exhibit excellent electrical characteristics     

High-performance automatic target recognition through data-specificVLSI

Under the Mojave configurable computing project, we have developed a system for achieving high performance on an automatic target recognition (ATR) application through the use of configurable computing technology. The ATR system studied here involves real-time image acquisition from a synthetic aperture radar (SAR). SAR images exhibit statistical properties which can be used to improve system performance. In this paper, the Mojave configurable computing system uses field programmable gate arrays (FPGA's) to implement highly specialized circuits while retaining the flexibility of programmable components. A controller sequences through a set of specialized circuits in response to real-time events. Computer-aided design (CAD) tools have been developed to support the automatic generation of these specialized circuits. The resulting configurable computing system achieves a significant performance advantage over the existing solution, which is based on application specific integrated circuit (ASIC) technology