Optimum Laguerre filter design technique for sigma-delta demodulators

As an alternative to conventional FIR filters, an optimal IIR filter architecture based on orthonormal Laguerre functions is proposed for Sigma-Delta (/spl Sigma/-/spl Delta/) demodulators. A Laguerre IIR filter design methodology is presented via the optimization of a quadratic function subject to a linear and a quadratic constraint. An efficient procedure to perform the optimization is discussed. The proposed IIR filter is easy to implement because it needs only a small number of components and therefore well suited for VLSI implementations. The impact of the selection of filter pole on the filter stability and phase linearity is discussed. The robustness issue of the Laguerre IIR filter is also addressed.