On the power implications of floating point addition in IIR filters

In floating point DSP applications, filtering of data samples is one of the most demanding operations. While the specification driven filter design delivers transfer functions satisfying target applications, certain implementations of these transfer functions can result in filters exhibiting various undesirable artifacts. This work addresses the characterization of the relative power implications of floating point Direct form II and Transposed Direct form II IIR filters. In programmable DSP applications, (compared to Transposed Direct form II realizations), Direct form II realizations offers better power reduction as far as the power implications of the floating point adder segment of DSPs are concerned. During filtering of white noise samples, the alignment driven data path switchings of transposed realizations had been found to be around 3 to 4 times that of direct form realizations. Performance of the same experiment involving audio samples substantiates the above findings.