Arthur Bernard Williams

Bio: Arthur Bernard Williams is an academic researcher. The author has contributed to research in topics: Electronic filter & Digital filter. The author has an hindex of 4, co-authored 4 publications receiving 402 citations.

Electronic filter design handbook

Abstract: Chapter 1: Introduction to Modern Network Theory Chapter 2: Selecting the Response Characteristic Chapter 3: Low-Pass Filter Design Chapter 4: High-Pass Filter Design Chapter 5: Bandpass Filters Chapter 6: Band-Reject Filters Chapter 7: Networks for the Time Domain Chapter 8: Refinements in LC Filter Design and the Use of Resistive Networks Chapter 9: Design and Selection of Inductors for LC Filters Chapter 10: Component Selection for LC and Active Filters Chapter 11: Normalized Filter Design Tables Chapter 12: Introduction to Digital Filters Chapter 13: Finite Impulse-Response Filters Chapter 14: Infinite Impulse-Response Filters Chapter 15: Multirate Digital Filters Chapter 16: Digital Filter Technology Chapter 17: Switched-Capacitor Filters Chapter 18: Introduction to Microwave Filters APPENDIX A: DISCRETE SYSTEMS MATHEMATICS APPENDIX B: SOFTWARE SUMMARY INDEX

Automated synthesis of analog electrical circuits by means of genetic programming

Abstract: Analog circuit synthesis entails the creation of both the topology and the sizing (numerical values) of all of the circuit's components. This paper presents a single uniform approach using genetic programming for the automatic synthesis of both the topology and sizing of a suite of eight different prototypical analog circuits, including a low-pass filter, a crossover filter, a source identification circuit, an amplifier, a computational circuit, a time-optimal controller circuit, a temperature-sensing circuit, and a voltage reference circuit. The problem-specific information required for each of the eight problems is minimal and consists of the number of inputs and outputs of the desired circuit, the types of available components, and a fitness measure that restates the high-level statement of the circuit's desired behavior as a measurable mathematical quantity. The eight genetically evolved circuits constitute an instance of an evolutionary computation technique producing results on a task that is usually thought of as requiring human intelligence.

An Improved Repetitive Control Scheme for Grid-Connected Inverter With Frequency-Adaptive Capability

Abstract: The power quality of grid-connected inverters has drawn a lot of attention with the increased application of distributed power generation systems. The repetitive control technique is widely adopted in these systems, due to its excellent tracking performance and low output total harmonic distortion (THD). However, in an actual system, the ratio of the sampling frequency to the grid frequency cannot always maintain an integer, and then, the resonant frequencies of the repetitive control technique will deviate from the real grid fundamental and harmonic frequencies. This will degrade the performance of the system, particularly when the grid frequency varies. Even if the ratio is a fixed integer, the auxiliary function for stabilization in the conventional repetitive control technique will also increase the steady-state tracking error and THD of the system. In this paper, an improved repetitive control scheme with a special designed finite impulse response (FIR) filter is proposed. The FIR filter cascaded with a traditional delay function can approximate the ideal repetitive control function of any ratio. The proposed scheme varies the FIR filter according to varied grid frequency and maintains its resonant frequencies matching the grid fundamental and harmonic ones. Finally, the simulation and experimental results show that the improved repetitive control scheme can effectively reduce the tracking error and compensate harmonics of the inverter systems.

Meta‐materials with wideband negative permittivity and permeability

Abstract: Recently, electromagnetic materials with negative permittivity and permeability values (sometime called “media with negative refraction index”) have been given much attention in the literature. Negative values of the material parameters can be achieved in composite media near resonances, which implies very dispersive properties. The material parameters are complex numbers to account for dissipation, and the real parts can be negative only in narrow frequency bands. Here, we show that this limitation can be relaxed in composite materials with active inclusions. It is proven that, using small dipole and loop antennas loaded by certain simple electronic circuits as composite inclusions, the material behaves as an effective medium with real negative parameters in wide frequency bands. Similarly, thin sheets of negative materials can be simulated by strip or patch arrays loaded by active circuits. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 163–165, 2001.

Experimental studies on realization of fractional inductors and fractional-order bandpass filters

Abstract: This paper presents the hardware realization and performance study of fractional inductors of order 0<α<2. The fractional inductors used in this work have been realized with the help of general impedance converter circuit and fractional capacitors. Impedance characterization of fractional inductors with different exponents has been carried out experimentally. Also a generalized approach to design a fractional-order bandpass filter is discussed in this work. The fractional-order bandpass filter consists of a series combination of a resistor, a fractional inductor of order 1<α<2, and a fractional capacitor of order 0<β<1. The performance of fractional-order bandpass filters has been studied and compared with corresponding integer-order filters through both experimentation and simulation. Copyright © 2014 John Wiley & Sons, Ltd.

Approximate formulae for numerical inversion of Laplace transforms

Abstract: Most methods for the numerical calculation of inverse Laplace transformations f(t) = L−1[F(s)] have serious limitations concerning the class of functions F(s) that can be inverted or the achievable accuracy. The procedures described in the paper can be used to invert rational as well as irrational or transcendental functions of the complex variable s. The required accuracy of the results can be enhanced without changing the algorithm, only at the cost of a longer computation time. The described methods were verified with many examples including transients in lumped/distributed systems with sections of lossy multiconductor transmission lines or with distributed RC elements. © 1998 John Wiley & Sons, Ltd.