Multiplier-free decimator algorithms for superresolution oversampled converters

A class of efficient linear-phase finite impulse response (FIR) decimators for attenuating the out-of-band noise generated by a high-order sigma-delta analog-to-digital modular is introduced. The stopband attenuation of these decimators is more than 120 dB. The decimators contain no general multipliers and a few data memory locations, thereby making them easily VLSI-realizable. This is achieved by using several decimation stages, with each stage containing a small number of delays and arithmetic operations. Some of the stages are constructed using low-order building blocks which are combined to give a selective filter using a few additional tap coefficients and adders. The output sampling rate of these decimators is the minimum possible one, and the proposed decimators can be used, with very slight changes, for many oversampling ratios. These decimators highly attenuate the undesired out-of-band signal components of the input signal, thus significantly relaxing the antialiasing prefilter requirements