A digital filter function requires many coefficient multiplications. Instead
of
implementing the multiplications individually as multipliers, they may be implemented
using traverse or shift operations. This approach uses the relation among the coefficients
of the digital filter to reduce required hardware. A disclosed digital filter uses
scalers and sample combiners for processing samples of a digital input stream.
Each scaler scales a respective input sample from one of the combiners, preferably
by a different power of 2. The combining circuits combine sets of samples, from
the digital input stream and from the digital output of the filter, to form the
input samples for processing by the scalers. An adder totals the respective scaled
values, to form the digital output stream of the filter. The digital filter may
be used in a variety of digital signal processing applications, but is particularly
useful in low-power portable devices, such as wireless spread-spectrum receivers.