A SIMPLE APPROACH TO THE DESIGN OF LINEAR-PHASE FIR DIGITAL-FILTERS WITH VARIABLE CHARACTERISTICS

A class of linear phase digital filters is discussed for which the filter coefficients are simple functions of the parameters determining the desired frequency response. In the case of lowpass or highpass filters, the 6 dB cutoff frequency is the parameter considered. Bandpass and bandstop filters are characterized by the center frequency and the bandwith measured from the 6dB cutoff frequencies. Notch filters with a first-order zero at the notch frequency are discussed. The filters are variable over nearly the whole frequency range from zero to half the sampling frequency. Due to direct control of filter coefficients, the length of the filter does not change when it is made variable.