CMOS stacked folded differential structure power amplifier for high power RF application

This article describes the feasibility of a Power Amplifier (PA) in 0.13 μm CMOS technology from STMicroelectronics for high power applications. To obtain a high output power with a good linearity, a new topology called Stacked Folded Differential Structure (SFDS) is proposed. It allows obtaining similar power performances to a PA with DAT in a lower die area. This PA provides 23 dBm of maximum output power (P_max) with 20% of power added efficiency (PAE) at 1.95 GHz. The linear gain is equal to 11 dB and the output power at 1 dB compression point (OCP₁) achieves 21 dBm. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

K competing queues with geometric service requirements and linear costs: The μc-rule is always optimal

In this note, a discrete-time system of K competing queues with geometric service requirements and arbitrary arrival patterns is studied. When the cost per slot is linear in the queue sizes, it is shown that the μc-rule minimizes the expected discounted cost over the infinite horizon.     

AN AFM PROBE CONTROLLER DESIGN BASED ON μ‐SYNTHESIS

The atomic force microscope (AFM) is one of the most important tools for measuring atomic resolution. The AFM system maintains constant force between a tip and the sample in order to track the sample topography. The controller that maintains the constant interaction force plays a significant role in measurement accuracy. This paper presents a μ‐synthesis controller design to deal with model uncertainty and establish a measurement error bound. The system's nonlinearity and the set‐point drift are lumped into a multiplicative uncertainty. The performance bound allows specification of the error magnitude over the frequency range. Simulation results show that the proposed control can tolerate uncertainties. The error spectrum from the experiments shows consistency with the design specifications. Images were taken to compare μ‐synthesis control with a well‐tuned PID control at a 480μm/s scan rate. The results verify the outstanding performance of the μ‐controller.     

ROBUST NONLINEAR CONTROLLER DESIGN FOR A LONGITUDINAL FLIGHT CONTROL PROBLEM

In this paper, the H_∞ approximate I/O linearization formulation and μ‐synthesis are employed to design a nonlinear controller for an aircraft longitudinal flight control problem. We propose modified nonlinear H_∞ controller formulas to approximately linearize the system and use μ‐synthesis to address tracking, regulation, and robustness issues.     

Lazy Solid Texture Synthesis

Existing solid texture synthesis algorithms generate a full volume of color content from a set of 2D example images. We introduce a new algorithm with the unique ability to restrict synthesis to a subset of the voxels, while enforcing spatial determinism. This is especially useful when texturing objects, since only a thick layer around the surface needs to be synthesized. A major difficulty lies in reducing the dependency chain of neighborhood matching, so that each voxel only depends on a small number of other voxels. Our key idea is to synthesize a volume from a set of pre‐computed 3D candidates, each being a triple of interleaved 2D neighborhoods. We present an efficient algorithm to carefully select in a pre‐process only those candidates forming consistent triples. This significantly reduces the search space during subsequent synthesis. The result is a new parallel, spatially deterministic solid texture synthesis algorithm which runs efficiently on the GPU. Our approach generates high resolution solid textures on surfaces within seconds. Memory usage and synthesis time only depend on the output textured surface area. The GPU implementation of our method rapidly synthesizes new textures for the surfaces appearing when interactively breaking or cutting objects.     

Variance Soft Shadow Mapping

We present variance soft shadow mapping (VSSM) for rendering plausible soft shadow in real‐time. VSSM is based on the theoretical framework of percentage‐closer soft shadows (PCSS) and exploits recent advances in variance shadow mapping (VSM). Our new formulation allows for the efficient computation of (average) blocker distances, a common bottleneck in PCSS‐based methods. Furthermore, we avoid incorrectly lit pixels commonly encountered in VSM‐based methods by appropriately subdividing the filter kernel. We demonstrate that VSSM renders high‐quality soft shadows efficiently (usually over 100 fps) for complex scene settings. Its speed is at least one order of magnitude faster than PCSS for large penumbra.     

Textures on Rank‐1 Lattices

Storing textures on orthogonal tensor product lattices is predominant in computer graphics, although it is known that their sampling efficiency is not optimal. In two dimensions, the hexagonal lattice provides the maximum sampling efficiency. However, handling these lattices is difficult, because they are not able to tile an arbitrary rectangular region and have an irrational basis. By storing textures on rank‐1 lattices, we resolve both problems: Rank‐1 lattices can closely approximate hexagonal lattices, while all coordinates of the lattice points remain integer. At identical memory footprint texture quality is improved as compared to traditional orthogonal tensor product lattices due to the higher sampling efficiency. We introduce the basic theory of rank‐1 lattice textures and present an algorithmic framework which easily can be integrated into existing off‐line and real‐time rendering systems.     

A Multidirectional Occlusion Shading Model for Direct Volume Rendering

In this paper, we present a novel technique which simulates directional light scattering for more realistic interactive visualization of volume data. Our method extends the recent directional occlusion shading model by enabling light source positioning with practically no performance penalty. Light transport is approximated using a tilted cone‐shaped function which leaves elliptic footprints in the opacity buffer during slice‐based volume rendering. We perform an incremental blurring operation on the opacity buffer for each slice in front‐to‐back order. This buffer is then used to define the degree of occlusion for the subsequent slice. Our method is capable of generating high‐quality soft shadowing effects, allows interactive modification of all illumination and rendering parameters, and requires no pre‐computation.