number of channels are inputted through the gui management unit 71 n algorithm trees are generated a bandwidth parameter and frequency information for each of the n algorithm trees are input n filter outcomes generated through the algorithm are combined together in the mux filter 10 so that an outcome is output with reference to fig2 the coefficient calculation unit 73 may calculate a frequency the number of channels and a bandwidth depending on parameters inputted from the outside through the gui management unit 71 based on the algorithm and the calculation function stored in the coefficient storage unit 72 to exemplarily and briefly explain the process of filtering a signal in the digital filter 40 as to a filter coefficient of the fir filter 41 a bandwidth and a frequency can be changed in a unit of minimum 10 khz depending on parameters inputted through the gui management unit 71 and n bands can be selected the coefficient calculation unit 73 selects a filter coefficient having a pre stored basic filter characteristic depending on parameters inputted by the user and a corresponding band size in the coefficient storage unit 72 and moves a frequency to generate a desired filter coefficient in this case a filter coefficient of each of the bands is generated depending on the number of bands selected by the user the generated filter coefficients are combined together to calculate a final filter coefficient thereafter based on the calculated coefficient information is sent to the fir filter 41 through the filter output controller 74 to.