A novel bit-serial design of comb filters for oversampling A/D converters
Nianxiong Tan, Sandra Eriksson, Lars Wanhammar · 2002
The non-recursive algorithm of comb filters suitable for bit-serial implementation is described in this paper. It performs decimation on the oversampling delta-sigma modulator output in several stages by utilizing the commutative rule. Each stage performs very simple FIR filtering and decimates the output by a factor of 2. A novel bit-serial design based on this algorithm is then presented. It features regularity and area and power-consumption efficiency. It also provides the possibility of higher frequency operation than existing designs. As an example, a comb filter of the response sinc/sup 3/(f) with a decimation ratio 32 has been designed in AMS' 1 /spl mu/m double-metal CMOS process. It contains only 4500 transistors even by using standard static gates and occupies about 1.1 mm/sup 2/ active chip area.>