Using carry-save adders in low-power multiplier blocks

Abstract

For a simple multiplier block FIR filter design, we compare the effects on power consumption of using direct versus transposed direct forms, tree versus linear structures and carry-save (CS) versus carry-ripple (CR) adders (for which multiplier block algorithms have been designed). We find that tree structures offer power savings, as expected, as does transposition in general but not always. Selective use of CS adders is shown to offer power savings provided that care is taken with their deployment. Our best result is with a direct form CR/CS hybrid. The need for new multiplier-block design algorithms is identified.