Design of Optimal Engineering Filters

This paper is to realize the equivalent wave approximation of the FIR filter, based on its main characteristics, by application of the alternate theorem, and generalizing its mathematical model. Moreover, it can realize stop band controllable dent. This approximation is arbitrary. Setting up the dent in the noise power density area can best eliminate the general noise power output of the filter so as to improve the filter characteristics. This provides a relatively good theory and a practical method for the engineering design of a FIR filter.