Sequential design of IIR digital filters for low-power DSP applications

A method for the design of linear-phase IIR digital filters for low-power applications is proposed. In this method, the digital filter is implemented as a cascade arrangement of 2nd-order sections. The first section is designed through optimization techniques so as to satisfy as far as possible the overall required specifications. A second section is then added which is designed through optimization techniques so that the first two sections satisfy as far as possible the overall required specifications. This process is repeated until a multisection filter is obtained which satisfies the required specifications under the most critical circumstances imposed by the application at hand. The minimum number of sections required to process a particular input signal can then by switched on through the use of a simple adaptation mechanism and, in this way, the power consumption can be minimized. This design structure is achieved by formulating the design on the kth section as a weighted quadratic programming problem with stability, amplitude response, and the first k-1 sections as constraints.