The Distributed Half Band Filter (DHBF) is a 'down-convert and decimate' filter, primarily intended for use as the first stage in very high sample rate DSP systems. Data is presented at the DHBF input from a high speed sampling system (typically an A to D and anti-aliasing filter) and the input signal is down-converted to base-band with the frequency range +/- fs/4 (where fs is the input sample rate).