A high-quality digital filter instrument

A high-quality real-time low power dissipation 12-bit low-pass digital-filter instrument is described. It is a hardware version of a recently proposed multirate ladder structure which can be implemented entirely without digital multipliers. The frequency response of the filter is user programmable and is determined by an operating sequence stored in a read-only memory. A numerical technique is described for determining the operating sequence corresponding to a particular low-pass response. Measured frequency responses are shown for four different cutoff frequencies between 2 and 5.5 kHz) for the fifth-order filter instrument.