Identification of the natural resonance frequencies of a conducting sphere from a measured transient response

It is shown that the imaginary parts of the first six natural resonant frequencies of a spherical scatterer can be determined quite accurately from measurements of both its surface charge and scattered field responses. This is an important step in verifying the practicality of characterizing low-Q targets by means of their resonance frequencies. Results for the real parts of the natural frequencies are not highly accurate. However, these values do not need to be known with great precision, since radar target discrimination schemes can be geared to use information primarily from the imaginary parts. It is important to note that target identification does not depend on the extraction of resonant frequencies in real time under adverse noise conditions. Rather, the resonance frequencies of the targets are assumed to be a priori knowledge, determined in a controlled, low-noise laboratory environment.<
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