An Algorithm for Computing Design Parameters of IFIR Filters with Low Complexity

Algoritmo para el Cálculo de Parámetros de Diseño de Filtros IFIR de Baja Complejidad

Javier Díaz–Carmona¹, Gordana Jovanovic–Dolecek² and José A. Padilla–Medina¹.

¹ Technological Institute of Celaya, Ave. Tecnologico y G. Cubas, Postal Code 38010, Celaya, Guanajuato, México. email: jdiaz@itc.mx ; apadilla@itc.mx.

² National Institute of Astrophysics Optics and Electronics, P. O. Box 51 and 216, Postal Code 72000, Puebla, Puebla, México. email: gordana@inaoep.mx.

Article received on August 17, 2006
Accepted on November 11, 2006

Abstract

This paper describes an algorithm for computing design parameters of Interpolated FIR (IFIR) digital filters with a low complexity (small number of products per output sample). The interpolation function is performed by a sharpened cascaded Recursive–Running Sum (RRS) filter, where the sharpening technique is used to improve the RRS frequency domain characteristics. Given the desired filter specifications and a chosen sharpening polynomial, the proposed algorithm computes the maximum IFIR filter interpolation factor and the minimum number of stages of the RRS filter in such a way that the overall structure meets the desired specifications with the minimum complexity.

Keywords: Narrowband filtering, Digital filters, IFIR, Sharpening technique, RRS filter.

Resumen

En este artículo se describe un algoritmo para calcular los parámetros de diseño de filtros digitales FIR interpolados (IFIR) con una complejidad baja (número pequeño de productos por muestra de salida). La función de interpolación se lleva a cabo mediante un filtro de suma en línea recursivo (RRS) moldeado, en donde la técnica de moldeo se aplica para mejorar las características en el dominio de la frecuencia del filtro RRS. Dadas las especificaciones deseadas del filtro y un polinomio de moldeo, el algoritmo propuesto calcula el máximo factor de interpolación del filtro IFIR y además el número mínimo de etapas en cascada del filtro RRS de manera que la estructura completa satisfaga las especificaciones con la mínima complejidad.

Palabras Clave: Filtrado de banda angosta, Filtros digitales, IFIR, Técnica de moldeo, Filtro RRS.

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