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Abstract

A method and apparatus for performing complex digital filters. According to one aspect of the invention, a method for performing a complex digital filter is described. The complex digital filter is performed using a set of data samples and a set of complex coefficients. In addition, the complex digital filter is performed using a inner and outer loop. The outer loop steps through a number of corresponding relationships between the set of complex coefficients and the set of data samples. The inner loop steps thorough each complex coefficient in the set of complex coefficients. Within the inner loop, the data sample corresponding to the current complex coefficient (the complex coefficient currently identified by the inner loop) is determined according to the current corresponding relationship (the corresponding relationship currently identified by the outer loop). Then, in response to receiving an instruction, eight data elements are read and used to generate a currently calculated complex number. These eight data elements were previously stored as packed data and include two representations of each of the components of the current complex coefficient and its current corresponding data sample. Each of these data elements is either the positive or negative of the component they represent. As a result of the manner in which these eight data elements are stored, the currently calculated complex number represents the product of the current complex coefficient and its current corresponding data sample. The currently calculated complex number is then added to the current output packed data.

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