A linear, time-varying system framework for noniterativediscrete-time band-limited signal extrapolation

A technique for the analysis and design of noniterative algorithms for discrete-time, band-limited signal extrapolation is described. The approach involves modeling the extrapolation process as a linear, time-varying (LTV) system, or filter. Together with a previously developed Fourier theory for LTV systems, this model provides a frequency-domain transfer function representation for the extrapolation system. This representation serves as a powerful tool for characterizing and comparing the reconstruction properties of several well-known least squares optimal algorithms for band-limited extrapolation. Moreover, the frequency-domain setting provides a conceptually attractive means for understanding the process of extrapolation itself. Additionally, a least squares approximation methodology for designing LTV filters for band-limited extrapolation is developed. The design technique is shown to unify a broad class of algorithms for extrapolating discrete-time data and, further, to provide a means for designing new and improved extrapolation algorithms     

Optimization of the Matching Network for a Hybrid Coupler Phase Shifter

A new theory is presented for how to find the optimum data for a transmission line used as a matching network for a hybrid coupler phase shifter. The theory gives a smaller phase-shift error and a greater bandwidth than already known methods. Two methods for equalization of the diode losses for a hybrid coupler phase shifter are described.     

CMOS circuit optimization

In this paper, optimization algorithms for CMOS circuits are described, from the propagation delay time viewpoint. The propagation delay time for a CMOS in erter is calculated for a step function input. A classical model of I–V characteristics for a MOSFET and the worst case Sah model for inter-electrode capacitances of a MOSFET are used for this deduction.     

Comparing between estimation approaches: admissible and dominating linear estimators

We treat the problem of evaluating the performance of linear estimators for estimating a deterministic parameter vector x in a linear regression model, with the mean-squared error (MSE) as the performance measure. Since the MSE depends on the unknown vector x, a direct comparison between estimators is a difficult problem. Here, we consider a framework for examining the MSE of different linear estimation approaches based on the concepts of admissible and dominating estimators. We develop a general procedure for determining whether or not a linear estimator is MSE admissible, and for constructing an estimator strictly dominating a given inadmissible method so that its MSE is smaller for all x. In particular, we show that both problems can be addressed in a unified manner for arbitrary constraint sets on x by considering a certain convex optimization problem. We then demonstrate the details of our method for the case in which x is constrained to an ellipsoidal set and for unrestricted choices of x. As a by-product of our results, we derive a closed-form solution for the minimax MSE estimator on an ellipsoid, which is valid for arbitrary model parameters, as long as the signal-to-noise-ratio exceeds a certain threshold.     

Uniaxial chiral quarter-wave polarisation transformer

The uniaxial chiral medium is a generalisation of the well-studied isotropic chiral media. It is obtained when microscopic helices with parallel axes are positioned in a host dielectric in random locations. Solutions for the dispersion equation and for the eigenwaves for a uniaxial chiral medium were recently found. Here the authors consider the polarisation properties of a transverse wave propagating through a uniaxial chiral slab. The results give a simple possibility for constructing a polarisation transformer for changing the polarisation of a propagating plane wave.<>     

The Analysis of a Class of Non-Series Parallel Redundant Systems

Two analysis techniques for use in the study of a class of non-series parallel, dual channel systems are presented. The first technique is a method for obtaining an approximate solution for the system. It is based on a systematic analysis of first- and second-order failure modes and involves the use of matrix algebra. The second technique is a method for generating the exact solution from the approximate solution. This method involves a transformation which converts the system into a logically equivalent system. An exact solution for the transformed system is derived and is shown to be the exact solution for the original system.     

Modeling testing-strategies for yield enhancement of multichipmodule systems

This paper presents analytic models for evaluating test-strategy (TS) for yield enhancement of systems manufactured using fault-tolerant (FTol) multichip modules (MCM) for massively parallel computing. Several methods for testing FTol-MCM have been proposed, but there is little analytic evaluation. This paper uses a novel Markov model to compute the yield. Unlike a previous method which uses a binomial distribution, our TS can use intermediate tests (Intmed-T). This paper shows an efficient TS with a modest level of redundancy to achieve 100% first-pass MCM yield for a particular system. Two methods using Intmed-T for FTol-MCM are proposed and analyzed. When Intmed-T are used for all mounted chips, FTol-MCM with more than a few chips require known-good chips of at least a 99.9% probability-good for achieving a high yield. An efficient TS with a modest level of redundancy can exist for achieving a 100% first-pass MCM yield for a particular system. A yield-analysis model using the least recently tested (LRT) TS in this paper provides a very good figure-of-merit due to its cost, delivery, number of tests, and reliability benefits for current technology. Extensive parametric results for the analysis show that LRT-TS can be applied to calculate the overall yield for FTol-MCM more accurately and efficiently, thereby improving the system reliability     

A programmable integrated digital controller for switching converters with dual-band switching and complex pole-zero compensation

The design of a 0.6-/spl mu/m CMOS programmable integrated digital PID controller for a buck converter is presented. Several novel features are implemented. These include: 1) a dual-band switching scheme for sampling the output voltage for better output resolution; 2) a dual-band switching PWM generator with a modified tapped delay line for area efficiency; 3) a VCO driving a counter to serve as an ADC; 4) a programmable PID compensator employing variable integration times for enhancing accuracy and stability; and 5) complex pole-zero cancellation in extending the bandwidth of the control loop. The converter is designed for variable output applications, and the fast digital loop achieves a tracking time of 50 /spl mu/s for a 1-V step change of the reference voltage. The converter switches at 1 MHz and attains a maximum efficiency of 90% when delivering a load of 125 mW.     

The synchronization of variable-length codes

Many variable-length codes exhibit a tendency for resynchronization to occur automatically following any error. However, attempts to identify an underlying synchronization mechanism, and to accurately predict the expected synchronization delay, for even quite specific variable-length codes, appear to have been largely unsuccessful. The present paper explores a novel method for estimating the synchronization performance for a wide variety of variable-length codes, based on the T-Codes. T-Codes are a class of self-synchronizing codes, which typically synchronize within 2-3 codewords by a mechanism that derives from a recursive T-augmentation construction. It is observed that the T-Code mechanism for synchronization is followed, more or less, by other variable-length codes wherever substantial numbers of codewords are shared with a T-Code set. T-augmentation itself provides a means for assessing the contribution individual codewords make to the overall synchronization process for a T-Code set. Thus codeword differences between sets may be specifically evaluated to estimate the synchronization performance of a variable-length code set from a closely related T-Code set     

Automotive Noise from a Motorway: Part II, Analysis

Modeling for automotive traffic radio noise is presented. A model is basic for single running vehicles with ignition-system radio emissions on a roadway. An equivalent source for the impulsive noise, continuously distributed over the distance traversed by a vehicle, with the same source density, is assumed to be acting only for the differential time length which is required for a vehicle to run through the differential distance. Based upon this model, the impulse amplitude distributions at the input to a narrowband receiver are derived mathematically, when a vehicle runs through a definite distance at a constant speed. Applications of the derived formula for the distribution are discussed in detail for the cases: 1) when the traversed distance varies, 2) when the emitting characteristic of impulses of the ignition system varies, and 3) when many vehicles with various emitting characteristics of impulses run on the roadway for a time long enough to provide statistically stationary data for automotive traffic radio noise.     

Spatially Adaptive Estimation via Fitted Local Likelihood Techniques

This paper offers a new technique for spatially adaptive estimation. The local likelihood is exploited for nonparametric modeling of observations and estimated signals. The approach is based on the assumption of a local homogeneity of the signal: for every point there exists a neighborhood in which the signal can be well approximated by a constant. The fitted local likelihood statistics are used for selection of an adaptive size and shape of this neighborhood. The algorithm is developed for a quite general class of observations subject to the exponential distribution. The estimated signal can be uni- and multivariable. We demonstrate a good performance of the new algorithm for image denoising and compare the new method versus the intersection of confidence interval (ICI) technique that also exploits a selection of an adaptive neighborhood for estimation.     

Transmission-Line Properties of a Strip on a Dielectric Sheet on a Plane

The subject is a strip Iine formed of a strip and a parallel ground plane separated by a dielectric sheet (commonly termed "microstrip"). Building on the author's earlier papers all the significant properties are formulated in explicit form for practical applications. This may mean synthesis and/or analysis. Each formula is a close approximation for all shape ratios, obtained by a gradual transition between theoretical forms for the extremes of narrow and wide strips. The effect of thickness is formulated to a second-order approximation. Then the result is subjected to numerical differentiation for simple evaluation of the magnetic-loss power factor from the skin depth. The transition formulas are tested against derived formulas for overlapping narrow and wide ranges of shape. Some of these formulas are restated from the earlier derivations and others are derived herein. The latter include the second-order approximation for a narrow thin strip, and a close approximation for a narrow or wide square cross section in comparison with a circular cross section. Graphs are given for practical purposes, showing the wave resistance and magnetic loss for a wide range of shape and dielectric. For numerical reading, the formulas are suited for programming on a digital pocket calculator.     

Binary lattice vector quantization with linear block codes andaffine index assignments

We determine analytic expressions for the performance of some low-complexity combined source-channel coding systems. The main tool used is the Hadamard transform. In particular, we obtain formulas for the average distortion of binary lattice vector quantization with affine index assignments, linear block channel coding, and a binary-symmetric channel. The distortion formulas are specialized to nonredundant channel codes for a binary-symmetric channel, and then extended to affine index assignments on a binary-asymmetric channel. Various structured index assignments are compared. Our analytic formulas provide a computationally efficient method for determining the performance of various coding schemes. One interesting result shown is that for a uniform source and uniform quantizer, the natural binary code is never optimal for a nonsymmetric channel, even though it is known to be optimal for a symmetric channel     

Combinatorial Analysis of Check Set Construction for Algorithm-Based Fault Tolerance Systems

Algorithm-based fault tolerance (ABFT) is a low-cost system-level concurrent error detection and fault location scheme. The design problem for an ABFT system is concerned with the construction of a check set for detecting errors or faults. In this paper, we analyze the construction of check sets from a combinatorial perspective, and propose a necessary and sufficient condition for the design of a check set that detects a given number of errors. We also propose a new bound for detecting three errors for algorithm-based fault tolerance systems.     

Monolithic integrated direction-sensitive flow sensor

A manolithic integrated direction-sensitive flow sensor for measuring the velocity of gas or liquid flow is described. Its operation is based on the transfer of heat from a heated chip to a flowing fluid. Temperature differences on the chip are a measure for the flow velocity and flow direction in a plane parallel with the chip's surface. The sensor can be embedded in a wall, for example, in a wall of a tube conducting a fluid flow, and can be shielded from a direct contact with the fluid. Measurements are stated for velocities in a range below 3 m/s for air at room temperature.     

Analysis of stochastic gradient tracking of time-varying polynomialWiener systems

This paper presents analytical and Monte Carlo results for a stochastic gradient adaptive scheme that tracks a time-varying polynomial Wiener (1958) system [i.e., a linear time-invariant (LTI) filter with memory followed by a time-varying memoryless polynomial nonlinearity]. The adaptive scheme consists of two phases: (1) estimation of the LTI memory using the LMS algorithm and (2) tracking the time-varying polynomial-type nonlinearity using a second coupled gradient search for the polynomial coefficients. The time-varying polynomial nonlinearity causes a time-varying scaling for the optimum Wiener filter for Phase 1. These time variations are removed for Phase 2 using a novel coupling scheme to Phase 1. The analysis for Gaussian data includes recursions for the mean behavior of the LMS algorithm for estimating and tracking the optimum Wiener filter for Phase 1 for several different time-varying polynomial nonlinearities and recursions for the mean behavior of the stochastic gradient algorithm for Phase 2. The polynomial coefficients are shown to be accurately tracked. Monte Carlo simulations confirm the theoretical predictions and support the underlying statistical assumptions     

The transient electromagnetic field of a pulsed line source located above a dispersively reflecting surface

An exact representation for the transient field of a pulsed line source above a plane reflecting surface is obtained as a finite integral over the transient plane-wave solution for complex angles of incidence. When applied to the reflection from a conducting half-space, a solution for the transient field is obtained as a finite double integral, which permits accurate calculations in a minimum of computer time. Comparison with early-time and late-time approximations available in the literature shows that there is a wide range of times for which neither is accurate.     

Synthesis of Bashkow's a matrix for the general RC circuit

For many uses, a convenient formulation for solving a circuit is Bashkow's A matrix. The circuit formulation then becomes x? = Ax. Given this circuit formulation, the synthesis of a circuit for a particular A matrix is of interest. Such a synthesis is accomplished by finding the diagonalising matrix for A, finding the form of the square incidence submatrix for a general tree in this case, and then using a linear-programming technique.     

A posteriori error learning in nonlinear adaptive filters

The authors provide relationships between the a priori and a posteriori errors of adaptation algorithms for real-time output-error nonlinear adaptive filters realised as feedforward or recurrent neural networks. The analysis is undertaken for a general nonlinear activation function of a neuron, and for gradient-based learning algorithms, for both a feedforward (FF) and recurrent neural network (RNN). Moreover, the analysis considers both contractive and expansive forms of the nonlinear activation functions within the networks. The relationships so obtained provide the upper and lower error bounds for general gradient based a posteriori learning in neural networks     

Thermoelectric Module Design Under a Given Thermal Input: Theory and Example

Established thermoelectric theory enables direct calculation of the power output and conversion efficiency if the temperature difference across a module is given. However, in some applications such as those using a radioisotope or solar radiation as a heat source, the thermal input remains constant while the temperature difference varies with the geometry of the thermoelectric module. In this paper, a theoretical framework for thermoelectric module design under a given thermal input is presented. It provides a convenient approach for module geometry optimization. The usefulness of the theory is demonstrated through a design study, in which an appropriate thermoelement length for a solar thermoelectric system is determined by considering conflicting requirements for a longer length to obtain a greater temperature difference and for a shorter length to produce a larger power output.