Multiplier-less IIR filter synthesis algorithms to trade-off the delay and the number of adders

As the complexity of digital filters is dominated by the nuniber of multiplications, many works have focused on minimizing the complexity of multiplier blocks that compute the constant coefficient niultiplications required in filters. Although the complexity of multiplier blocks is significantly reduced by using efficient techniques such as decomposing multiplications into simple operations and sharing common subexpressions, previous works have not considered the delay of multiplier blocks which is a critical factor in the design of complex filters. In this paper, we present algorithms to minimize the complexity of multiplier blocks under the given delay constraints and apply them to infinite impulse response (IIR) filter synthesis. By analyzing multiplier blocks in view of delay, three delay reduction methods are proposed and combined into previous algorithms. Since the proposed algorithm can generate multiplier blocks that meet the specified delay, a trade-off between delay and hardware complexity is enabled by changing the delay constraints. Experimental results show that the proposed algorithms can reduce the delay of inultiplier blocks at the cost of a little increase of complexity.