Dual frequency miniature microstrip antenna

A single-feed dual frequency compact microstrip antenna with a shorting pin is described. This new antenna configuration gives a large variation in frequency ratio of the two operating frequencies, without increasing the overall size of the antenna     

A simple recursive formula for calculating the S-parameters offinite periodic structures

A simple and efficient recursive formula to calculate the S-parameters of large, finite periodic structures is introduced. The technique utilizes measured or computed S matrices of structures with a small number of periods. The formula is verified on a simple rectangular waveguide with periodic gratings. Results from the formula are plotted against similar results obtained from finite-difference time-domain (FDTD) simulations, and they show excellent agreement. This formula can be used to compute the S-parameters of large microwave or optical periodic structures, which, by virtue of their finiteness may not be open to the application of periodic boundary conditions     

Time domain Green's functions for lossy and dispersive multilayered media

We have introduced a fast method of calculating the time domain Green's functions for multilayered media. In this paper, we demonstrate the use of this method to compute the scalar potential Green's function for a multilayer lossy dispersive medium on a PEC ground. The strength of the method lies in obtaining the Green's function for many source-to-field distances /spl rho/ and time instances t simultaneously. It only takes 6 min 28 s to compute 100/spl times/336=33 600 space time Green's function points in Matlab on a Pentium III 867 MHz processor with 1 GB of RAM for a multilayered lossy dispersive medium.     

A precise sensor fault detection technique using statistical techniques for wireless body area networks

One of the major challenges in wireless body area networks (WBANs) is sensor fault detection. This paper reports a method for the precise identification of faulty sensors, which should help users identify true medical conditions and reduce the rate of false alarms, thereby improving the quality of services offered by WBANs. The proposed sensor fault detection (SFD) algorithm is based on Pearson correlation coefficients and simple statistical methods. The proposed method identifies strongly correlated parameters using Pearson correlation coefficients, and the proposed SFD algorithm detects faulty sensors. We validated the proposed SFD algorithm using two datasets from the Multiparameter Intelligent Monitoring in Intensive Care database and compared the results to those of existing methods. The time complexity of the proposed algorithm was also compared to that of existing methods. The proposed algorithm achieved high detection rates and low false alarm rates with accuracies of 97.23% and 93.99% for Dataset 1 and Dataset 2, respectively.     

Modeling visual attention's modulatory aftereffects on visual sensitivity and quality evaluation.

With the fast development of visual noise-shaping related applications (visual compression, error resilience, watermarking, encryption, and display), there is an increasingly significant demand on incorporating perceptual characteristics into these applications for improved performance. In this paper, a very important mechanism of the human brain, visual attention, is introduced for visual sensitivity and visual quality evaluation. Based upon the analysis, a new numerical measure for visual attention's modulatory aftereffects, perceptual quality significance map (PQSM), is proposed. To a certain extent, the PQSM reflects the processing ability of the human brain on local visual contents statistically. The PQSM is generated with the integration of local perceptual stimuli from color contrast, texture contrast, motion, as well as cognitive features (skin color and face in this study). Experimental results with subjective viewing demonstrate the performance improvement on two PQSM-modulated visual sensitivity models and two PQSM-based visual quality metrics.     

Compact Models of Spreading Resistances for Electrical/Thermal Design of Devices and ICs

Building upon our recent work (IEEE Electron Device Lett., vol. 26, pp. 909-912, Dec, 2005), we present simple and continuous closed-form models for several rectangular and circular spreading resistance geometries encountered in electrical/thermal design of devices and integrated circuits. The resistance geometries considered involve current/heat flow between parallel contacts of rectangular or circular shape and concentric or eccentric nature, between a horizontal and a vertical stripe, and between a horizontal circular contact and a surrounding vertical cylindrical contact. The modeling procedure involves normalization of the spreading resistance with respect to its value under 1D flow conditions, followed by a curve-fit of the variation of this normalized resistance with contact area in terms of physical parameters. The resistance models may also be used to estimate the reciprocal of capacitance of similar insulator-electrode geometries, by replacing the resistivity by the reciprocal of the insulator permittivity.     

Generation of Scattering Functions for Mobile Communication Channel: A Computer Simulation Approach

In this paper, an algorithm of generation of thescattering function by computer simulation for the WSSUSurban mobile communication channel is studied. Thescattering function, which contains much valuable information of the channel, is calculatedthrough three approaches. The empirical measuredparameter database and recommended standard methods areused to generate the scattering function as the firstand second approaches. An in-service measurement ofthe GSM network is performed in Singapore, in thefrequency range 935-960 MHz using the Rohde and SchwarzChannel Sounder. The data collected are used for the calculation, as the third approach. Thefour main characteristics of the channel, the Dopplerspread B_d, the multipath spreadT_m, the coherence time t, and thecoherence bandwidth f, are observed. The computer-calculated scattering function isshown to be an accurate and effective tool forsimulation of WSSUS channels. As a result, a softwarepackage is developed and utilized in the X-Windowenvironment for the simulation of the urban mobilecommunication channel. It can meet most of therequirements of both the system designers and theservice providers.     

Identifying technology horizons for strategic investment decisions

Technology investment models usually assume that a known number of technologies will appear in the future, though their appearance, cost, and revenue parameters may be uncertain. In practice, however, it is not always clear how many future technologies or periods need to be considered. We introduce the concept of a technology horizon, which we define as the minimum number of future technologies and future periods that need to be considered to guarantee that the optimal decision would not change even if additional technologies or periods worth of data were to be considered. We also allow the costs and revenue of existing technologies in our model to vary depending on the latest technology introduced. Further, we allow for implementation costs, which enables us to model situations where it may cost more to leapfrog technologies than if one were to buy intervening technologies. We then provide a fast algorithm to identify such technology horizons     

On the validity of unintentional doping densities extracted using Mott–Schottky analysis for thin film organic devices

The organic electronic devices are often understood invoking the concept of ‘unintentional doping’. However, the applicability and usefulness of this controversial concept is not very clear and is under much recent debate. In this work, we revaluate the validity of this concept through careful experiments and detailed numerical simulations. Specifically, we use the Capacitance Voltage (CV) measurement of pentacene devices as a testbed to unravel the role of injecting electrodes and unintentional doping (if any). Indeed, our results indicate that the CV of pentacene capacitors can be solely understood in terms of properties of the contact electrodes. The unintentional doping, if present, has an inconsequential role in device performance. Our conclusions indicate that, often, an incorrect interpretation of CV results would lead to unphysical values of unintentional doping and have obvious implications towards the fundamental understanding of organic semiconductor device physics, modeling, and characterization; thus resolving many ambiguities in literature by providing a consistent interpretation through a coherent conceptual framework.