Showing papers in "IEEE Transactions on Circuits and Systems in 2008"

Switched-Capacitor/Switched-Inductor Structures for Getting Transformerless Hybrid DC–DC PWM Converters

Abstract: A few simple switching structures, formed by either two capacitors and two-three diodes (C-switching), or two inductors and two-three diodes (L-switching) are proposed. These structures can be of two types: ldquostep-downrdquo and ldquostep-up.rdquo These blocks are inserted in classical converters: buck, boost, buck-boost, Cuk, Zeta, Sepic. The ldquostep-downrdquo C- or L-switching structures can be combined with the buck, buck-boost, Cuk, Zeta, Sepic converters in order to get a step-down function. When the active switch of the converter is on, the inductors in the L-switching blocks are charged in series or the capacitors in the C-switching blocks are discharged in parallel. When the active switch is off, the inductors in the L-switching blocks are discharged in parallel or the capacitors in the C-switching blocks are charged in series. The ldquostep-uprdquo C- or L-switching structures are combined with the boost, buck-boost, Cuk, Zeta, Sepic converters, to get a step-up function. The steady-state analysis of the new hybrid converters allows for determing their DC line-to-output voltage ratio. The gain formula shows that the hybrid converters are able to reduce/increase the line voltage more times than the original, classical converters. The proposed hybrid converters contain the same number of elements as the quadratic converters. Their performances (DC gain, voltage and current stresses on the active switch and diodes, currents through the inductors) are compared to those of the available quadratic converters. The superiority of the new, hybrid converters is mainly based on less energy in the magnetic field, leading to saving in the size and cost of the inductors, and less current stresses in the switching elements, leading to smaller conduction losses. Experimental results confirm the theoretical analysis.

A 12-Bit Ratio-Independent Algorithmic A/D Converter for a Capacitive Sensor Interface

Abstract: This paper describes a ratio-independent algorithmic analog-digital (A/D) converter architecture that is insensitive to capacitance ratio, amplifier offset voltage, amplifier input parasitics, and flicker noise. It requires only one differential amplifier, a dynamic latch, six capacitors, 36 switches, and some digital logic. The prototype 12-bit, 40-kS/s A/D converter (ADC) with an active die area of 0.041 mm2 is implemented in a 0.13-mum CMOS. The power dissipation is minimized using a dynamically biased operational amplifier. With a 68.4-muW power dissipation, the ADC achieves 80.2-dB spurious-free dynamic range and 63.3-dB signal-to-noise and distortion ratio.

Quantum-Noise Limited Distance Resolution of Optical Range Imaging Techniques

Abstract: The most common optical distance imaging methods (triangulation, interferometry and time-of-flight ranging) can all be described in a unified way as linear shift-invariant systems in which the determination of distance corresponds to the measurement of a spatial or temporal phase. Since the ultimate precision of such a phase measurement is limited by quantum noise of the involved photons or photocharges, the eventual distance resolution of the three optical ranging methods depends in the same way on quantum noise. Evidence from literature supports our basic assertion that photon and photocharge numbers have a Poisson distribution under most experimental conditions. This allows us to derive our main result that the quantum-noise limited distance resolution of the three optical ranging methods is proportional to the inverse of the signal's modulation amplitude times the square root of the background level. The equation for the precision of the three optical distance measurement techniques contains the method's experimental parameters in a single factor, from which the optimum distance range of the three techniques can easily be deduced: 1 nm-1 mum for interferometry, 1 mum-10 m for triangulation, > 0.1 m for time-of-flight ranging, if visible or near infrared light is used.

A Hybrid Coarse/Fine Layered Multicast Scheme Based on Hierarchical Bandwidth Inference Congestion Control

Abstract: Traditional approaches to receiver-driven layered multicast apply coarse-grain layered congestion control, which enables each receiver to adjust its receiving rate to match the available bandwidth. However, this restricts the scalability of fine-grain scalable video coding. In this paper, we present an approach that facilitates bandwidth inference congestion control in a hybrid coarse/fine layered multicast scheme for multimedia delivery. One-way delay trend detection has proven effective in explicitly or implicitly estimating end-to-end available bandwidth. Using a hierarchical layered probing scheme and a delay trend detection method, we have developed a congestion control protocol for fine-grain layered multicast. Combining this protocol with scalable video coding, we present a framework that achieves efficient scalable video streaming over heterogeneous networks. The performance of our hybrid coarse/fine layered multicast scheme is evaluated by network simulations and the video coding efficiency.