Bessel filter

About: Bessel filter is a research topic. Over the lifetime, 656 publications have been published within this topic receiving 16808 citations.

Active filter hardware design & performance for the DIII-D plasma control system

Abstract: The digital plasma control system (PCS), currently in operation on the DIII-D tokamak, requires inputs from a large number of sensors. Due to the nature of the digitizers and the relative noisy environment from which these signal are derived, each of the 32 signals must be conditioned via an active filter. Two different types of filters, Chebyshev and Bessel with fixed frequencies: 100 Hz Bessel was used for filtering the motional Stark effect diagnostic data. 800 Hz Bessel was designed to filter plasma control data and 1200 Hz Chebyshev is used with closed loop control of choppers. The performance of the plasma control system is greatly influenced by how well the actual filter responses match the software model used in the control system algorithms. This paper addresses the various issues facing the designer in matching the electrical design with the theoretical.

Some design methods for two‐dimensional digital filters with complex coefficients in consideration of linear phase characteristics

Abstract: In designing a two-dimensional digital filter with special consideration of the phase characteristics, particularly the group delay characteristics, a very high-order filter is generally required. This paper extends the coefficients of the filter from real to complex and describes a design technique for comparatively low-order, two-dimensional, circularly symmetric filters with consideration of phase characteristics. First, the method of transforming a two-dimensional input signal into an analytic signal is described and then the design technique of two kinds of complex coefficient filters which use the properties of analytic signals is discussed. In the first kind variable transformation to a 1-D real coefficient FIR filter is used to obtain a 2-D FIR filter with complex coefficients. It has the merits of permitting independent setting of the sharpness of cutoff characteristics and circular symmetry. In the other kind of complex coefficient filter a recursive digital filter is obtained by using an all-pole filter having constant group delay in the passband of the transfer function and having a 2-D complex coefficient mirror image polynomial. It always has a constant group delay unrelated to the values of the coefficients and the overall group delay is also constant. Moreover, in this paper, design examples based on these methods are given and the validity of our methods is shown.

Lie analysis of the Webster horn equation with application to audio object recognition

Abstract: The Webster horn equation describes the pressure wave in a duct of slowly varying cross section. We discuss symmetry reductions and exact solutions of the Webster horn equation using the classical Lie method of infinitesimals. The particular case of the exponential horn is examined and a complete set of reductions and solutions is formulated. The generation of a complete set of solutions using Lie analysis produces a set of group transformations. Particular attention is given to a new solution found, which contains an exponentially decaying Bessel function. The use of these group transformations as a tool for audio object recognition is also explored. Results indicate that the decaying Bessel function solution provides a particularly useful insight into exponential horn object recognition. Practical results are presented which indicate the group transformations offer an exciting new mechanism for identifying a specific audio object in a mixed audio scene.

G m -C Fractional Bessel Filter Of Order ( $1+\alpha$ )

Abstract: The paper discusses the design and circuit realization of a low-pass fractional Bessel filter of order ( $1+\alpha$ ) using the inverse-follow-the-leader-feedback (IFLF) structure. The transfer function of the Bessel filter is verified for correctness using MATLAB software. The circuit realization of Bessel filter using voltage controlled current source (VCCS) behavioral model of $G_{m}$ -block is validated using Cadence software. The flexibility to adjust the cut-off frequency for different values of $\alpha$ has been verified. The group delay and step response plots for different values of $\alpha$ are presented.