Ivan Krstić

Design of IIR Multiple-Notch Filters with Symmetric Magnitude Responses About Notch Frequencies

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.

Chained-Function Filter Synthesis Based on the Legendre Polynomials

A new kind of filter called Legendre chained-function (LCF) filter with characteristic function given by the product of low-degree Legendre orthogonal polynomials (seed functions) is studied in this paper. LCF filter magnitude response exhibits unequal ripple level in the passband compared to Chebyshev chained-function filter with identical edge ripple factor at the passband edge. A proper combination of seed functions, i.e., a product of them, is used to control the maximum ripple in the passband, which affects the return loss, selectivity and a group delay characteristics of a filter. By selecting one of the possible combinations of seed functions (thus obtaining various degrees of freedom in filter design), filters with improved performances compared to traditional approximation techniques can be obtained. The degrees of freedom increase if the degree of filter increases. Compared to existing Chebyshev chained-function (CCF) filters, whose performances are also presented, and Butterworth function filters as a special case of both LCF and CCF filters, the new family of LCF filters has many advantages. A table summarizing properties of CCF and LCF filters is given for design purpose.

The implementation of two channel IIR quadrature mirror filter bank based on residue arithmetic

Design of two-channel quadrature mirror filter (QMF) bank constructed by real infinite impulse response (IIR) digital all-pass filter is considered. Residue number system offers parallel processing and digital hardware implementation for binary operation of addition, subtraction and multiplication. There is no carry propagation between these operations. Hence, devices operating in this principle inherit properties of high speed and low power consumption. However, this properties makes overflow detection difficult during any operation. This paper discusses the application of RNS in designing the infinite impulse response (IIR) filter.