Design of efficient FIR filters with minimal delay

A new design method for approximately linear phase narrow-band lowpass and highpass FIR filters is presented. Also an efficient filter structure is introduced for realising the designed filters. This structure is based on a cascade of linear and non-linear phase FIR filters having transfer functions expressable as integer powers of the unit delay. The overall implementation requires significantly less multiplications than conventional direct form FIR filters. Moreover, the delay of the new filters is only fractions of what can be attained using pure linearphase FIR filters. It is shown by means of an example that the new design method and realisation results in virtually linear phase FIR highphase filters which are computationally efficient and have short response times.