Baxter F. Womack

The Analysis of Respiratory Sinus Arrhythmia Using Spectral Analysis and Digital Filtering

Respiratory sinus arrhythmia is the phenomenon by which respiration modulates heart rate in normal humans and in many animals. This investigation was divided into the following three categories: 1) the development of a mathematical model relating respiration to those variations that it causes in heart rate; 2) the use of digital filtering techniques to attenuate fluctuations in heart rate which are due to respiration; and 3) the development of methods that use only heart rate to get information about respiration.

An Adaptive Pattern Classification System

Adaptive pattern classification is the assignment of patterns to classes based on typical patterns or training samples, used by the system to determine the decision procedure. The system is adaptive in the sense that the decision procedure is optimized according to some criterion of the systems performance on the training samples. An adaptive pattern classification system is described that does not require a priori knowledge of the probability density of the pattern vectors for each class, as do the classical statistical techniques. Any decision rule, consisting of a discriminant function, that is a linear combination of arbitrary scalar functions of the pattern vector, may be chosen on the basis of a priori knowledge about the classes, engineering judgment, and economic considerations. The system optimizes itself by adjustment of the decision parameters according to a weighted mean-square-error performance criterion, using a multivariable search technique. The proposed performance criterion is well suited for self-optimizing search procedures. It also has the property that, as the number of training samples approaches infinity, the resulting disciminant function belongs to the class of discriminant functions, chosen at the outset, which approximates the optimum Bayes discriminant function with minimum variance. Some results from simulation studies are presented which include comparison with classical statistical techniques.

Orthonormal pulses for high data rate communications in indoor UWB systems

In this letter, we propose novel pulses which not only meet the power spectral mask of the Federal Communications Commission (FCC) for indoor Ultra-wideband (UWB) systems but also preserve orthogonality at the correlation receiver. The proposed pulses are derived from a parametric closed-form solution. Thus, multiple orthonormal pulses that comply with the FCC mask without additional frequency shifting or bandpass filters can be generated for high data rate communications or multiple access schemes. Simulation results demonstrate that high data rate communication is achieved by the proposed orthonormal pulses via pulse shape modulation and pulse position modulation.

Brief paper: Discrete time adaptive control of linear systems with preload nonlinearity

In this note a method is presented for doing discrete time adaptive control of a nonlinear system which is given by a cascade connection of a preload nonlinearity followed by a linear system. It is shown that the algorithm will ensure that the closed loop system is globally convergent with a specific residue and stable for both the deterministic and stochastic cases.

Stability analysis of a discrete-time adaptive control algorithm having a polynomial input

Stability and convergence are shown for adaptive control of a cascade connection of a finite-odd order polynomial followed by a linear system. The main point is the establishment of the linear boundedness condition of the key technical lemma [7].

On the controllability of a class of nonlinear systems

For the system dx/dt = f(x, t) + B(t)u with f(x, t) defined in a bounded region in the state space, sufficient conditions for the initial states to be controllable are given.

Power Loading Using Order Mapping in OFDM Systems With Limited Feedback

This letter proposes an approximate waterfill power loading scheme using limited feedback in orthogonal frequency division multiplexing (OFDM) systems. The proposed technique achieves nearly the capacity of optimal waterfill power loading, while significantly reducing feedback by using order information for the subcarrier channel gains. Furthermore, the proposed power loading technique can circumvent the practical shortcomings of previous limited feedback power loading techniques by simply exploiting order mapping and interpolation. The advantages are particularly visible at low SNR or for many subcarriers, both of which will be very common in emerging wireless broadband OFDM standards.

Performance Analysis of OT-MRC Over I.I.D. Nakagami and Non-I.I.D. Rayleigh Fading Channels

This paper presents the performance analysis of a conditional diversity combining scheme, which is called output-threshold maximum ratio combining (OT-MRC), over the independent identically distributed Nakagami-m with integer m and independent but not necessarily identically distributed Rayleigh fading channels. Based on the closed-form expressions for the statistics, the authors analyze the performance of the OT-MRC systems and compare it with that of the conventional MRC systems. They exploit the tradeoff between complexity and performance in this scheme over the Nakagami fading channels and see the effect of unbalance of the fading gains over multiple diversity branches on the performance of OT-MRC. They show, from some numerical examples, that the OT-MRC scheme, when compared with the MRC scheme, can reduce the complexity significantly without losing the required performance

A two-parameter adaptive system using a sinusoidal test signal

A linear control system with two variable parameters is considered in this paper. Identification of the state of the basic system is achieved by a high frequency sinusoidal test signal. The magnitude and phase angle of the perturbed output signal are used in two adaptive loops to detect changes in system gain and the location of a nondominant pole. A simple approach to the prediction of interloop coupling is presented. The results of simulating this adaptive system on an analog computer are given.

Metal Wet Etch Issues and Effects in Dual Metal Gate Stack Integration

This article discusses metal wet etch issues and their effects on high-k/metal films in dual work function metal gate stack integration. A versatile process using metal wet etch has been demonstrated to integrate dual metal gate complementary metal oxide semiconductor (CMOS) devices (Z. B. Zhang et al., in 2005 Symposia on VLSI Technology and Circuits, Kyoto, Japan, June 14-18, 2000). Different high-k/metal films, combinations of films, etch selectivity, thermal stability, interactions among the films, and finally, surface conditions have made the implementation of metal wet etch challenging. Here, representative results using HfO 2 , HfSiON, in situ steam generated silicon oxide (SiO 2 ), TiN, Ta, TaSiN, TaCN, TiSiN, amorphous silicon (a-Si), and tetraethylorthosilicate in dual metal CMOS processing are presented.