Butterworth filter

About: Butterworth filter is a research topic. Over the lifetime, 6187 publications have been published within this topic receiving 69070 citations.

A Procedure for the Automatic Determination of Filter Cutoff Frequency for the Processing of Biomechanical Data

Abstract: This article presents and evaluates a new procedure that automatically determines the cutoff frequency for the low-pass filtering of biomechanical data. The cutoff frequency was estimated by exploiting the properties of the autocorrelation function of white noise. The new procedure systematically varies the cutoff frequency of a Butterworth filter until the signal representing the difference between the filtered and unfiltered data is the best approximation to white noise as assessed using the autocorrelation function. The procedure was evaluated using signals generated from mathematical functions. Noise was added to these signals so mat they approximated signals arising from me analysis of human movement. The optimal cutoff frequency was computed by finding the cutoff frequency that gave me smallest difference between the estimated and true signal values. The new procedure produced similar cutoff frequencies and root mean square differences to me optimal values, for me zeroth, first and second derivative...

Power system having a phase locked loop with a notch filter

Abstract: A power system having a phase locked loop (PLL) with a notch filter for synchronous reference frame sequence separation. The notch filter includes a generalized integrator tuned to the notch frequency. The output of the generalized integrator is summed with the filter input signal and the output of the summer is fed back to the integrator input. In one embodiment, the notch filter is programmable by a control signal generated in response to the filter output signal, thereby causing the filter to self-regulate to a frequency related to the PLL input signal. Illustrative power systems include active VAR generators and active rectifiers. One or more additional notch filters may be used to remove harmonic components from derived synchronous reference frame sequence components.

Subband acoustic feedback cancellation in hearing aids

Abstract: A new subband feedback cancellation scheme is proposed, capable of providing additional stable gain without introducing audible artifacts. The subband feedback cancellation scheme employs a cascade of two narrow-band filters Ai(Z)and Bi(Z)ng with a fixed delay, instead of a single filter Wi(Z)and a delay to represent the feedback path in each subband. The first filter, Ai(Z), is called the training filter, and models the static portion of the feedback path in ith subband, including microphone, receiver, ear canal resonance, and other relatively static parameters. The training filter can be implemented as a FIR filter or as an IIR filter. The second filter, B?I?(Z), is called a tracking filter and is typically implemented as a FIR filter with fewer taps than the training filter. This second filter tracks the variations of the feedback path in the i?th? subband caused by jaw movement or objects close to the ears of the user.

EMI filter design

Abstract: With today’s electrical and electronics systems requiring increased levels of performance and reliability, the design of robust EMI filters plays a critical role in EMC compliance. Using a mix of practical methods and theoretical analysis, EMI Filter Design, Third Edition presents both a hands-on and academic approach to the design of EMI filters and the selection of components values. The design approaches covered include matrix methods using table data and the use of Fourier analysis, Laplace transforms, and transfer function realization of LC structures. This edition has been fully revised and updated with additional topics and more streamlined content. New to the Third Edition Analysis techniques necessary for passive filter realization Matrix method and transfer function analysis approaches for LC filter structure design A more hands-on look at EMI filters and the overall design process Through this bestselling book’s proven design methodology and practical application of formal techniques, readers learn how to develop simple filter solutions. The authors examine the causes of common- and differential-mode noise and methods of elimination, the source and load impedances for various types of input power interfaces, and the load impedance aspect of EMI filter design. After covering EMI filter structures, topologies, and components, they provide insight into the sizing of components and protection from voltage transients, discuss issues that compromise filter performance, and present a goal for a filter design objective. The text also includes a matrix method for filter design, explains the transfer function method of LC structures and their equivalent polynomials, and gives a circuit design example and analysis techniques. The final chapter presents packaging solutions of EMI filters.

Finite Impulse Response Filter Design

Abstract: This chapter introduces principles of the finite impulse response (FIR) filter design and investigates the design methods such as the Fourier transform method, window method, frequency sampling method, and optimal design method. Then the chapter illustrates how to apply the designed FIR filters to solve real-world problems such as noise reduction and digital crossover for audio applications.