Digital IIR integrator design using recursive Romberg integration rule and fractional sample delay

In this paper, a digital IIR integrator design based on the recursive Romberg integration rule and the fractional sample delay is investigated. Starting with trapezoidal integrators, the approximation error of the frequency response of digital integrators can be reduced recursively by using the Romberg rule. Although the proposed IIR digital integrators involve the implementation of the fractional sample delay, this problem is easily solved by applying the well-documented design techniques of the FIR Lagrange and IIR allpass fractional delay filters. These techniques lead to the transfer function of the IIR Romberg integrator without using the fractional sample delay. Several design examples are presented in order to demonstrate the effectiveness of the proposed method.