Natural resonances via rational approximants

An approach for locating the dominant complex natural resonances (poles) of scatterers or radiators is described. Admittance values, calculated using Richmond´s thin wire computer programs, at a regular grid of complex and real frequencies are fit by a rational function. Zeros of the resultant numerator and denominator polynomials then yield, respectively, the zeros and poles of the structure. The method is illustrated for resonances of straight and bent wire structures.