Frequency Response Measurements With Local Parametric Modeling

The concept of local parametric modeling has drawn renewed attention to frequency response function (FRF) measurements. Essentially, these approaches assume a particular parametric structure and approximate the FRF and the leakage errors in a small-frequency band around the frequency of interest. Following the successful application of the idea in the local polynomial method (LPM), the local rational method (LRM) was developed, replacing polynomial by rational approximating functions. The power of the LRM has previously been demonstrated in simulations and experiments, yet an explanation of the method's robustness to pole-zero cancellations was lacking. At the cost of increased computation, the LRM reduces the leakage errors with several orders of magnitude with respect to its alternatives while, under commonly encountered conditions, the sensitivity to disturbing noise remains competitive to that of the standard procedures. In this paper, we provide insight into the observed virtues of the proposed method.