Showing papers on "Bessel filter published in 1994"

The time-frequency distributions of nonstationary signals based on a Bessel kernel

Abstract: A kernel based on the first kind Bessel function of order one is proposed to compute the time-frequency distributions of nonstationary signals. This kernel can suppress the cross terms of the distribution effectively. It is shown that the Bessel distribution (the time-frequency distribution using Bessel kernel) meets most of the desirable properties with high time-frequency resolution. A numerical alias-free implementation of the distribution is presented. Examples of applications in time-frequency analysis of the heart's sound and Doppler blood flow signals are given to show that the Bessel distribution can be easily adapted to two very different signals for cardiovascular signal processing. By controlling a kernel parameter, this distribution can be used to compute the time-frequency representations of transient deterministic and random signals. The study confirms the potentials of the proposed distribution in nonstationary signal analysis. >

Modified Bessel nondiffracting beams

Abstract: Solutions of the scalar-wave equation that are based on modified Bessel functions are introduced. These functions are radially nonoscillating, unbound, and nondiffractive. Their propagation constant is larger than that of vacuum, meaning that there is an inverse Guoy effect or a phase velocity smaller than c. The beams are physically realized by apodization of the modified Bessel profiles by means of suitable window functions. When Gaussian apodization functions are used, axial decay is slower than in the Gaussian case and the case of ordinary Bessel counterparts. Super-Gaussian and circular apodization are also examined. In the latter case a persistent narrow axial lobe that also has a nondecaying character is encountered.

Further comments on the geometrical efficiency of a parallel-disk source and detector system

Abstract: A derivation is presented for a previously published formula, which determines the geometrical efficiency of a parallel-disk source and detector system. The formula involves an integral over a product of two Bessel functions. An algebraic approximation to the integral is also discussed.

Programmable operation transconductance amplifier

Abstract: A digitally programmable Bessel filter includes a plurality of serially connected stages or biquads with each biquad including a plurality of programmable operational transconductance amplifiers. The first stage of the filter provides an all pass equal amplitude response. Two stages provide pulse slimming (first and second derivatives of an input pulse), and three stages provides a sixth order Bessel low pass function. The operational transconductance amplifiers are controlled by a fine tuning control signal, and an array of integrating capacitors are selectively controlled by a coarse tuning signal. The fine tuning and coarse tuning signals are generated in a phase locked loop from a reference clock and a reference biquad which receives the reference clock.

Approximations to the radiation resistance and directivity of circular-loop antennas

Abstract: The purpose of this article is to derive approximate formulas for the radiation resistance (R), and the directivity (D) of circular loop antennas. It is shown that simple approximations to the Bessel functions can be employed, to accurately model the oscillatory behavior of the Bessel function integral for both small and intermediate-sized loop antennas. Furthermore, when these approximations are combined with the usual asymptotic contributions to the integral in the case of a large input parameter ka (a=loop radius, a=2/spl pi///spl lambda/) accurate and relatively simple results for R and D can be secured for all loop sizes. Numerical results can, if necessary, be obtained using a simple pocket calculator. >

Bessel functions: parallel display and processing.

Abstract: We present an optical setup that converts planar binary curves into two-dimensional amplitude distributions, which are proportional, along one axis, to the Bessel function of order n, whereas along the other axis the order n increases. This Bessel displayer can be used for parallel Bessel transformation of a signal. Experimental verifications are included.

Evaluating innite integrals involving Bessel functions of arbitrary order

Abstract: The evaluation of integrals of the formIn = R 1 0 f(x)Jn(x)dx is considered. In the past, the method of dividing an oscillatory integral at its zeros, forming a sequence of partial sums, and using extrapolation to accelerate convergence has been found to be the most ecien t technique available where the oscillation is due to a trigonometric function or a Bessel function of order n = 0; 1. Here, we compare various extrapolation techniques as well as choices of endpoints in dividing the integral, and establish the most ecien t method for evaluating innite integrals involving Bessel functions of any order n, not just zero or one. We also outline a simple but very eectiv e technique for calculating Bessel function zeros.

A CONTINUOUS-TIME FILTER AND EQUALIZER COMPRISING A PARASITIC-INSENSITIVE BiCMOS ACTIVE INTEGRATOR

Abstract: A fast parasitic-insensitive continuous-time filter and equalizer integrated circuit that uses an active integrator is described. Circuit techniques for excess-phase cancellation, and for setting the corner-frequency of the filter and equalizer are also described. These techniques result in a filter and equalizer chip with performance independent of process, supply, and temperature without employing phase-lock loops. This 20MHz 6th order Bessel filter and 2nd order equalizer operate from 5V, and generate only .24 % (-52dB) of total harmonic distortion when processing 2Vp-p differential output signals. The device is optimized to limit high-frequency noise and to amplitude equalize the data pulses in hard disk read-channel systems. The device supports data rates of up to 36Mbps, and is built in a 1.5ν/4GHz BiCMOS technology.

Pulsation diagnosing device using image

Abstract: PURPOSE:To provide a device for assisting a diagnosis on pulsation by a doctor with the use of an image data inference using an electrical signal CONSTITUTION:A pulsation diagnosing device is composed of a probe 200, a pulsation signal matching circuit 212, a low band pass circuit Bessel filter 213 having a linear phase characteristic, an analog/digital converting circuit 214, a computer system 215, a display unit 216, a pressure signal matching circuit 222, an analog/digital converting circuit 223 and a numerical value indicator 224