An introduction to digitial matched filters

In this introductory exposition, the class of noncoherent digital matcted filters (DMF´s) which are matched to AM signals is analyzed. Attention is focused on the special case of binary signals and one-bit digitization. Expressions are obtained relating output and input signal-to-noise ratios when the channel interference is additive and a) white Gaussian, b) incoherent and of constant amplitude, and c) coherent and of constant amplitude. These expressions are compared with expressions for the performance of the corresponding noncoherent analog matched filter under the same conditions Improvements in DMF performance obtained by thresold biasing and by dithering are investigated; it is shown that DMF´s can be made to outperform analog matched filters by proper use of the former technique. All theoretical results are corroborated by computer simulation.