Arithmetic transformations for increased maximal sample rate of bit-parallel bireciprocal lattice wave digital filters
Henry Ohlsson, Oscar Gustafsson, Lars Wanhammar · 2002
In this paper we propose an arithmetic transformation of first-order allpass lattice wave digital filter sections implemented with bit-parallel, carry-save arithmetic which increases the maximum sample rate. Such filter sections are the critical component of bireciprocal lattice wave digital filters which are efficient filter structures for sample rate conversion with factors of two. The proposed transformation reduces the sample period bound by up to 33% for CSDC coefficients. This is obtained with a coefficient with four nonzero bits, and, dependent on the value of the adaptor coefficient, at the expense of up to 28% more carry-save adders. An example is presented where an adaptor with a coefficient with two nonzero bits is implemented. This results in a reduction of the sample period bound with 25% with a 14% increase of the number of carry-save adders needed.