Showing papers on "Bessel filter published in 2001"
TL;DR: In this article, the use of useful properties of sine, spherical Bessel and reduced Bessel functions to simplify the application of the nonlinear D- and -transformations for accelerating the convergence of semi-infinite very oscillatory integrals and to reduce the calculation times keeping a high predetermined accuracy.
Abstract: This paper focuses on the use of useful properties of sine, spherical Bessel and reduced Bessel functions to simplify the application of the nonlinear D- and -transformations for accelerating the convergence of semi-infinite very oscillatory integrals and to reduce the calculation times keeping a high predetermined accuracy. Three-centre nuclear attraction integrals, which are one of the most difficult type involved in density functional theory methods when using a basis set of B functions, are evaluated using the new approach. The numerical results show the efficiency of the new method compared with other alternatives.
42 citations
TL;DR: This paper proposes to process the filter weights via a least-squares-based method in order to acquire optimum delay estimates even with short filter lengths.
25 citations
01 Apr 2001-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: The Auger Fluorescence Detector (AFD) as mentioned in this paper is a detector module consisting of an array of 20 -22 PMTs at the focal surface of a large-aperture telescope.
Abstract: The Auger Fluorescence Detector will allow to determine the longitudinal development of atmospheric showers in the range 10 19 –10 21 eV. A detector module comprises an array of 20 � 22 PMTs at the focal surface of a large-aperture telescope. Thirty such modules will be used. The PMTs pixel signal is variable in shape depending on the shower-eye geometry. The sky background light (BL) is also variable. We have developed an analog signal processor to obtain best energy and timing resolution despite those constrains. The Head Electronics (HE) bias the PMTs and keeps its pulsegain constant even for large BL. This is measured using a current-monitor of novel design. Both the signal pulse and the BL DC level are sent via a single twisted pair to the Analog Board (AB). The AB performs the compression of the 15–16 bit signal dynamic range into 12 bits of the FADC which follows the AB. A three-pole Bessel filter was adopted for antialiasing. The AB includes 16 bit sigma-delta chips to readout the BL DC level, and a test-pulse distribution system. # 2001 Elsevier Science B.V. All rights reserved. PACS: 29.40
16 citations
TL;DR: A magnetic field exposure system that has been used to test human subjects, caged or confined animals, and cell cultures and is limited by the maximum voltage of the amplifier (Bessel filter bypassed).
Abstract: To maximize the availability and usefulness of a small magnetic field exposure laboratory, we designed a magnetic field exposure system that has been used to test human subjects, caged or confined animals, and cell cultures. The magnetic field exposure system consists of three orthogonal pairs of coils 2 m square × 1 m separation, 1.751 m × 0.875 m separation, and 1.5 m × 0.75 m separation. Each coil consisted of ten turns of insulated 8 gauge stranded copper conductor. Each of the pairs were driven by a constant-current amplifier via digital to analog (D/A) converter. A 9 pole zero-gain active Bessel low-pass filter (1 kHz corner frequency) before the amplifier input attenuated the expected high frequencies generated by the D/A conversion. The magnetic field was monitored with a 3D fluxgate magnetometer (0–3 kHz, ± 1 mT) through an analog to digital converter. Behavioral monitoring utilized two monochrome video cameras (viewing the coil center vertically and horizontally), both of which could be video recorded and real-time digitally Moving Picture Experts Group (MPEG) encoded to CD-ROM. Human postural sway (standing balance) was monitored with a 3D forceplate mounted on the floor, connected to an analog to digital converter. Lighting was provided by 12 offset overhead dimmable fluorescent track lights and monitored using a digitally connected spectroradiometer. The dc resistance, inductance of each coil pair connected in series were 1.5 m coil (0.27 Ω, 1.2 mH), 1.75 m coil (0.32 Ω, 1.4 mH), and 2 m coil (0.38 Ω, 1.6 mH). The frequency response of the 1.5 m coil set was 500 Hz at ± 463 μT, 1 kHz at ± 232 μT, 150 μs rise time from −200 μTpk to + 200 μTpk (square wave) and is limited by the maximum voltage ( ± 146 V) of the amplifier (Bessel filter bypassed). Bioelectromagnetics 22:401–407, 2001. © 2001 Wiley-Liss, Inc.
12 citations
TL;DR: In this paper, a technique is presented that uses a combination of forward and backward recurrence for the computation of integer-order Hankel functions with complex-valued arguments, and it is shown that numerical round-off errors can lead to inaccurate results if Bessel functions of the first and second kinds are superimposed to obtain the desired Hankel function.
Abstract: The accurate computation of a series of integer-order Bessel functions is often required in applications in engineering and physics. Numerous authors have shown how a recurrence relationship can be used in the backward and forward directions to accurately compute integer-order Bessel functions of the first and second kinds, respectively, for real- valued arguments. However, significant round-off errors can result when these standard recurrence algorithms are employed and the argument for the Bessel function is complex valued. C. F. du Toit recently developed an algorithm that overcomes these numerical instabilities for Bessel functions of the first and second kinds. However, if one needs to compute integer-order Hankel functions with complex arguments, then we have found that numerical round-off errors can lead to inaccurate results if Bessel functions of the first and second kinds are superimposed to obtain the desired Hankel functions. To address this problem, a technique is presented in this paper that uses a combination of forward and backward recurrence for the computation of integer-order Hankel functions with complex-valued arguments.
11 citations
TL;DR: In this article, a complete orthonormal system was constructed for the Galerkin solution of the differential equation Lu = f on R + ǫ, where L is the Bessel operator.
9 citations
TL;DR: An extrapolation of sensitivity from the slopes reveals that sensitivity can be predicted by a simple model assuming detection to be mediated by a transfer function made up as a cascade of an even bandpass function and the disc pattern spectrum, as has been found previously using one dimensional luminance distributions.
Abstract: The detection of small radially symmetric targets was studied using a subthreshold summation paradigm. Small disc and disc-like patterns with diameters up to 0.6∘ were used for superposition on Bessel functions of zero order, subthreshold contrast and various spatial frequencies. Contrast interrelation functions prove linear over the whole range of contrasts used for the Bessel functions while their slopes show systematic variation with spatial frequency. An extrapolation of sensitivity from the slopes reveals that sensitivity can be predicted by a simple model assuming detection to be mediated by a transfer function made up as a cascade of an even bandpass function and the disc pattern spectrum, as has been found previously using one dimensional luminance distributions. Problems concerning the formation of pattern-specific radial symmetric filters are discussed.
6 citations
Journal Article•
TL;DR: In this article, the authors divide the quadrature of dual Bessel integration into [0,λ 0] and [λ 0,∞] and present an efficient algorithm to compute the Bessel function.
Abstract: Due to strong oscillation and slow decay of product term in dual Bessel integration,it is difficult to use ordinary numerical method for the quadrature of dual Bessel.In this paper we divide [0,∞) into [0,λ 0] and [λ 0,∞);In [λ 0,∞),the integration can be written as Fourier cosine and sine transformation by asymptotic expression of Hankel Function and it can be evaluated by fast algorthm.In [0,λ 0],the integration can be computed accurately through direct quadrature.But when we calculate a quantity the related dual Bessel integration with common argument,the algorithm mentioned above seem not to be efficient enough.In this case,according to derivative relation of Bessel function,the constant transformation of the integration in [0,λ 0] can be done and the changed into the integration of the Bessel function itself which can only be calculated only once.This algorithm has improved efficiency of calculation obviously for dual Bessel integration.
4 citations
Posted Content•
TL;DR: In this article, power series representations of the modified Bessel functions (McDonald functions) were derived using the relatively little known formalism of fractional derivatives, and the resulting summation formulae are believed to be new.
Abstract: Some power series representations of the modified Bessel functions (McDonald functions $K_{\alpha}$) are derived using the relatively little known formalism of fractional derivatives. The resulting summation formulae are believed to be new.
4 citations
06 May 2001
TL;DR: This paper shows that the original definition of e developed by Euler can be used as the basis of a delay approximation where all the poles have the same value and it is shown that either the group delay or step response can be optimised.
Abstract: This paper shows that the original definition of e developed by Euler can be used as the basis of a delay approximation where all the poles have the same value. Furthermore it is demonstrated that by splitting the Euler function into complex pole pairs, by the addition of an artificial variable /spl beta/, an additional degree of freedom can be introduced. Through optimisation of the value of /spl beta/ it is shown that either the group delay or step response can be optimised. This delay approximation when compared to a standard Bessel approximation is shown to provide acceptable performance for many applications. Furthermore, it offers the considerable practical benefit of being realisable as a cascade of identical building block elements when appropriate technologies (e.g. second order active filter blocks) are used.
2 citations
08 Jul 2001
TL;DR: In this article, the main features of the secondary mirror unit of the SOFIA telescope are described and a state space model derived from the mechanical and electrical equations of the system is introduced.
Abstract: SOFIA is a 2.5-m telescope to be carried on a special Boeing 747 for astronomic observations at altitudes of about 15,000 m. The paper describes the main features of the secondary mirror unit. The SOFIA secondary mirror needs active control for alignment along five degrees of freedom as well as for very fast chopping with a frequency up to 20 Hz. The SOFIA secondary mirror chopping mechanism and control system are described. A state space model derived from the mechanical and electrical equations of the system is then introduced. This model can be used for the design of a state space controller based on a pole placement algorithm, making the system to behave as a fourth order Bessel filter. To avoid overshoots due to current and voltage limitations, a variable speed limitation which is function of the position error is added to the controller.
23 Oct 2001
TL;DR: In this paper, a fully differential R-MOSFET-C fourth-order Bessel active lowpass filter employing passive resistances and current-steering MOS transistors as a variable resistance is proposed.
Abstract: A fully differential R-MOSFET-C fourth-order Bessel active lowpass filter employing passive resistances and current-steering MOS transistors as a variable resistance is proposed. This proposed implementation relies on the tunability of the current-steering MOS transistors operating in the triode region counteracting the concert deviation of resistance in integrated circuit manufacturing technology in order that the group delay of Bessel active filter could be designed accurately. 0.75 us group delay fourth-order Bessel lowpass filter, which is synthesized according to passive doubly terminated RLC prototype lowpass filter, demonstrates better than -65 dB THD with 100-kHz, 1.65-Vpp signal in 3.3 V 0.5 um CMOS technology.
06 Aug 2001
TL;DR: In this article, the phase and group delay functions of an Nth order digital Laguerre filter are derived and the group delay function of the filter can be written as a ratio of quadratic functions in the filter coefficients.
Abstract: This paper considers the design of a digital filter with prescribed magnitude and group delay specifications. First, we outline the derivation of the phase and group delay functions of an Nth order digital Laguerre filter and show that the group delay function of the filter can be written as a ratio of quadratic functions in the filter coefficients. Then, we formulate our filter design problem as a constrained L/sub 2/ space minimization problem in which the performance requirement on the group delay and magnitude in the passband are treated as constraints while minimizing the L/sub 2/ norm of the error function between the designed and the desired filters. Methods for solving the proposed nonlinear optimization problem axe outlined. Numerical results are presented to illustrate the usefulness of the proposed method. As a special case, corresponding results for general FIR filters axe also derived.
Patent•
23 Aug 2001
TL;DR: An optical modulator for the encoded data in NRZ mode modulation of the intensity of a light signal, comprising means for shaping said luminous signal including shaping means for obtaining a low bandwidth signal (618 ) from the input control signal (635) such as a Bessel filter of the fifth order and an electrical control unit (620), and a laser modulator (610) having a transfer function (630) favoring extinction ratio of the light signal resulting from (640).
Abstract: An optical modulator for the encoded data in NRZ mode modulation of the intensity of a light signal, comprising means for shaping said luminous signal including shaping means for obtaining a low bandwidth signal (618 ) from the input control signal (635) such as a Bessel filter of the fifth order and an electrical control unit (620), and a laser modulator (610) having a transfer function (630) favoring extinction ratio of the light signal resulting from (640).