Natural resonances via rational approximants

A rational approximant method for extracting dominant poles of radiators or scatterers from complex- and real-frequency admittance data is tested for two simple targets (a straight wire and a bent wire). The method of fitting a rational function to admittance data generated at complex frequencies is described, and the results obtained are compared with known pole locations. Percentage errors in these results are evaluated for the real and imaginary parts of low-order poles. The method is shown to be susceptible to the density and location of the complex frequencies used to obtain the admittance data.