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We apply the Cauchy method to interpolate/extrapolate the radar cross-section (RCS) data which is amplitude-only data over a given frequency band. This is accomplished by approximating the amplitude-only data by a ratio of two polynomials, the coefficients of which are calculated by using the total least squares (TLS) implementation of a singular value decomposition (SVD) technique so as to properly estimate the dimension of the null space. By applying the Cauchy method, the power spectrum of an electromagnetic system is represented by a set of symmetric pole and zero pairs in the -plane. Once these coefficients in the numerator and the denominator polynomials in the Cauchy method are computed using the amplitude-only data, the response can be interpolated/extrapolated over other frequencies of interest. Numerical examples are presented to illustrate the applicability of the Cauchy method in interpolating/extrapolating RCS data over a frequency band, including a method of generating the phase response from the amplitude-only data.