In many measurement applications, it is required to have notch filters that simultaneously possess a very selective magnitude response (high quality factor Q) and a transient response of short duration. However, increasing the quality factor also increases the duration of the transient process in the filter after the action of the excitation. This paper presents a new concept of digital IIR notch filters, whose quality factor changes with time. Owing to a temporary change in the value of the quality factor, the transient can considerably be reduced. Simulations verifying the effectiveness of the proposed Q-varying IIR notch filter are presented and compared with the performance of the traditional Q-constant filter using ECG signals with unwanted sinusoidal interference as a study case.

Digital $Q$ -Varying Notch IIR Filter With Transient Suppression

Dynamic compensation of load cell response: A time-varying approach

The aim of this work is to develop an automated system for skeletal bone age evaluation. Skeletal bone age assessment is a common and time-consuming task in pediatric radiology. We describe a system that implements the EMROI (epiphyseal/metaphyseal region of interest) extraction method by image processing techniques. Each EMROI is localized on the image, by using an analysis of its gray levels. Then the bones in the EMROI are extracted by using the DoG (difference of Gaussians) filter and enhanced using a novel adaptive thresholding obtained by histogram processing. Finally, the main features of these bones are extracted for the stage TW2 (tanner whitehouse) evaluation. Results obtained on a sample of 20 X-rays are discussed. With respect to the other existing automated approaches to compute the bone age, the proposed method requires less user feedback on system's settings and is very versatile since it doesn't depend strongly on features of the X-ray acquisition.

Epiphysis and Metaphysis Extraction and Classification by Adaptive Thresholding and DoG Filtering for Automated Skeletal Bone Age Analysis

One important problem of signal processing in measurement systems is designing a filter that possesses a linear-phase response and, at the same time, has a short transient state. This paper presents the methodology of varying, in the time parameters, a low-pass Bessel filter and a filter of a constant component. In the proposed filters, significant shortening of the transient state is achieved at the cost of a slight increase in oscillations. This paper also addresses the problems that are connected with continuous running of the filters with varying parameters. The presented approach allows better preservation of the edge shape, as compared with traditional filtering techniques. Typical filtering results are presented, which are obtained by simulations of selected structures of filters with varying parameters.

Selected Structures of Filters With Time-Varying Parameters

One of the important problems of signal processing is to design the filters which possess linear phase characteristics. This paper presents the concept of time-varying Butterworth filters with linear phase. The compensation of the phase characteristics is carried out with the aid of phase shifter which is cascade-connected to the structure of the original Butterworth filter given by the transfer function. The parameters of the phase shifter were calculated in this way that the group delay of the designed filter is possible constant in the filter pass---band. Time varying coefficients were introduced to the phase---compensated filter structure for the purpose of minimization of the filter transient state. This paper contains simulation results of proposed filters and comparison with classic circuits.

Phase-Compensated Time-Varying Butterworth Filters

The paper presents the methodology how to vary in time values omega0i = omega0i(t) in selected links of a structure of low-pass Bessel filters. In examinations of the filters a significant shortening of the transient state is achieved at the cost of slight increase in the oscillations. It allows to shorten time intervals of filtered signals. Typical filtration results are presented which are obtained by simulations of selected structures of filters with varying parameters

Bessel Filters with Varying Parameters

The paper presents the methodology how to vary in time values /spl omega//sub 0i/ = /spl omega//sub 0i/(t) selected links of a structure of low-pass Bessel filters In examinations of the filters a significant shortening of the transient state is achieved at the cost of slight increase in the oscillations It allows shortening time intervals of filtered signals Typical filtration results are presented which simulations of selected structures of filters with varying parameters obtain

Bessel filters with varying parameters

One of the important problems of analog signal processing is to design the filters which possess linear phase characteristics. This paper presents the concept of time?varying Butterworth filters with linear phase response. The compensation of the phase characteristics is carried out with the aid of a phase shifter which is cascade?connected to the structure of the classic Butterworth filter. The parameters of the phase shifter were calculated in this way that the group delay of the designed filter is possible constant in the filter passband. Time?varying coefficients were introduced to the phase?compensated filter structure for the purpose of minimization of the filter transient state in the sense of the settling time. This paper contains simulation results of the proposed filters and comparison with the classic circuits.

Dynamic Compensation of Phase Distortion in Time-Varying Butterworth Filters

One of the important problems of signal processing in measurement systems is to design a continuous-time filter that provides both a constant delay over the desired frequency band and a selective magnitude response, and at the same time ensures the transient of the designed filter as short as possible. In this paper, we propose a new theoretical method for dynamic shortening of transients in compensated continuous-time filters. Using the compensated Chebyshev filter, we introduce time-varying parameters to its structure for the purpose of the minimization of the transient that was lengthened because of the compensation process. Results verifying the effectiveness of the proposed method are presented and compared to the traditional filters.

J. Piskorowski

Papers

Bessel Filters with Varying Parameters

Bessel filters with varying parameters

Dynamic Compensation of Phase Distortion in Time-Varying Butterworth Filters

Dynamic Reduction of Transients Duration in Delay-Equalized Chebyshev Filters