Search

A new approach to the design of the nearly linear phase infinite impulse response low-pass differentiators using a parallel all-pass structure is discussed in this paper. The magnitude and phase responses of the proposed low-pass differentiators are first formulated as functions of the phase responses of the corresponding all-pass filters, and a set of equations is derived such that the magnitude response approximates the ideal one in the weighted Chebyshev sense both in the passband and the stopband. The maximum passband phase response linearity error is shown to be related to the maximum passband magnitude error and the value of an additional design parameter. Comparison with the existing nearly-linear phase infinite impulse response low-pass differentiators shows that the low-pass differentiators designed using the proposed method usually require less multiplications, which comes at the cost of a somewhat higher filter order and consequently higher group delay. However, as the reduced number of multiplications lead to lower power consumption if hardware implementation is considered, the proposed low-pass differentiators are an attractive alternative in applications where low group delay is not of crucial importance. [ABSTRACT FROM AUTHOR]

In this paper, design of infinite impulse response lowpass differentiators that can be realized by parallel connection of two allpass filters whose orders differ by two, where one of the allpass branches is pure delay, is considered. As adopted structure of proposed lowpass differentiators allows formulation of their magnitude and phase responses as functions of allpass filter phase response, a set of nonlinear equations in unknown allpass filter coefficients is derived and iteratively solved in a way that magnitude response approximates the ideal one in weighted Chebyshev sense, in both passband and stopband. On the other hand, passband phase response linearity is shown to be related to the maximum of the magnitude response, which can be directly controlled by an additional design parameter. Design examples reveal that proposed infinite impulse response lowpass differentiators of low order can have very low relative passband magnitude errors and nearly linear phases, while results of comparison with existing lowpass differentiators show that proposed differentiators usually require fewer multiplications. [ABSTRACT FROM AUTHOR]

A method for design of a new class of digital infinite impulse response filters realized as parallel connection of two all-pass filters is presented in this paper. A new approach to approximation of quadratic phase of all-pass filter at all frequencies is given. Chosen parallel structure offers opportunity for realization of filters with arbitrary shape phase. The presented algorithm is based on all-pass filter phase approximation. Phases of both all-pass filters approximate ideal quadratic phase in minimax sense at all frequencies. Such filters can be applied for chirp signal compression or expansion. Magnitude characteristic of described filters is very selective and elliptic-like. Obtained filters are compared with elliptic filter and group delay corrector in cascade. For the same specifications, much better results are achieved by the proposed filters. Parallel connection of all-pass filters introduces lower signal delay, and for a given maximal phase, approximation error demands less complex network. Examples to illustrate the proposed method are given. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

A method for design of linear phase notch IIR filters is presented in this paper. The filter is realized in the form of a parallel connection of two all-pass sub-filters. In order to achieve the resulting filter with an approximately linear phase in the pass-band, the applied all-pass sub-filters should be also with a linear phase. The desired amplitude characteristic of a resulting filter is obtained by all-pass sub-filter phase approximation. It can be achieved by applying either a pure delay or an IIR all-pass filter in one branch. If a pure delay is positioned in one branch, equiripple phase of all-pass sub-filter from the other branch is guaranteed for an equiripple amplitude characteristic of the resulting filter. Efficiency of the proposed algorithm is demonstrated on a few examples. The algorithm exhibits a fast convergence and an easy determination of initial values. In the case where IIR all-pass sub-filters are placed in both branches, the resulting amplitude characteristic satisfies all the prescribed demands, but the amplitude characteristic is not equiripple even when both all-pass sub-filters have equiripple phase. [ABSTRACT FROM AUTHOR]

The new 3D models of the prestressed symmetrical and unsymmetrical ultrasonic sandwich transducers are described in this article. The sandwich transducers are modeled through the application of a 3D matrix model of piezoceramic rings and discs, recently proposed by the authors. Theoretical analyses prove the proposed models as simple and easy to calculate, particularly suitable for the investigation of coupled vibrations cases. Experiments show that the measured resonance and antiresonance frequencies are in good agreement with the predicted results. Compared with traditional 1D models and methods, the results obtained by the proposed models matched better with the experimental results. [ABSTRACT FROM AUTHOR]

Summary: A noniterative method for the all‐pass–based design of infinite impulse response multiple‐notch filters is proposed. This method ensures that specifications regarding positions of notch, left‐ and right‐hand cutoff frequencies, are exactly met, leading to a symmetric magnitude response about notch frequencies. Passband magnitude response can be improved by increasing the order of the corresponding all‐pass filter. A noniterative method for the all‐pass–based design of infinite impulse response (IIR) multiple‐notch filters is proposed. This method ensures that specifications regarding positions of notch, left‐ and right‐hand cutoff frequencies, are exactly met, leading to a symmetric magnitude response about notch frequencies. Passband magnitude response can be improved by increasing the order of the corresponding all‐pass filter. [ABSTRACT FROM AUTHOR]

A novel all-pass-based infinite impulse response (IIR) digital multiple-notch filter design method is presented in this paper. The proposed method ensures that, for an arbitrary pass-bands ripple value, specifications regarding positions of notch, left- and right-hand cutoff frequencies are exactly met, which leads to symmetric magnitude responses about notch frequencies. Although iterative in its nature, proposed method requires a small number of iterations to find coefficients of the multiple-notch filter, making it very useful for designers. Since the magnitude response of the all-pass-based IIR multiple-notch filter is more sensitive in the stop-bands than in the pass-bands, sensitivity analysis along with simulation in limited word-length environment is performed. [ABSTRACT FROM AUTHOR]