1. A repeatable filter cell comprising: a coefficient input stage having at least two coefficient inputs for receiving respective input coefficients, a means for selecting one of the input coefficients, and a coefficient output for providing the selected coefficient as output of the coefficient input stage, a mixer stage having at least two data value inputs for receiving respective input data values, a means for selecting one of the input data values, a multiplier means for receiving the selected coefficient from the coefficient input stage and the selected input data value and multiplying the selected input data value by the selected coefficient to form a mixer stage product, and a product output for providing the mixer stage product as output of the mixer stage, an accumulator delay stage having at least one input for receiving at least one input accumulation value, a selectively variable delay means for imposing a selected delay on the input accumulation value, and an accumulation delay output for providing the selectively delayed input accumulation value as output of the accumulator delay stage, and a summation stage having an input for receiving the accumulator delay stage output, an input for receiving the mixer stage output, a means for summing the accumulation value and the mixer stage output, and a summation stage output for providing the sum of the accumulation value and the mixer stage output as output of the filter cell.