CASCADED INTEGRATOR COMB FILTER WITH ARBITRARY INTEGER DECIMATION VALUE AND SCALING FOR UNITY GAIN

摘要

We disclose a CIC digital filter having an arbitrary-integer decimation rate. The filter has a shifter (110) connected to its input. The shifter (110) receives a shift control input, where the shift control input is pre-computed as equal to the integer portion of 2 raised to the base-2 logarithm of the gain of the CIC filter. There is a multiplier (100) connected between the input and the shifter (110). In other embodiments, the multiplier (100) could be connected between the input and the shifter (110). Sequentially-connected integrator (130) functions are connected to the shifter (110) or multiplier (100); a decimation function receives input from the integrator (130) functions; and sequentially-connected differentiator (150) functions receive input from the decimation function. The decimation function has a selectable rate equal to any integer between 1 and a number equal to the predetermined maximum decimation value. The multiplier (100) is configured to compute the product of each input data sample by a correction factor; the correction factor being pre-computed as equal to the fractional portion of 2 raised to the base-2 logarithm of the gain of the CIC filter, so as to correct the gain of the CIC filter for decimation values not a power of 2.