Time-Domain System for Identification of the Natural Resonant Frequencies of Aircraft Relevant to Electromagnetic Compatibility Testing

摘要

A method of measuring the natural resonant frequencies of a structure is described. The measurement involves irradiating this structure, in the case a helicopter, with an impulsive electromagnetic (EM) field and receiving the echo reflected from the helicopter. Resonances are identified by using a mathematical algorithm based on Prony's method to operate on the digitized reflected signal. The measurement system consists of special TEM horns, pulse generators, a time-domain system, and prony's algorithm. The frequency range covered is 5 megahertz to 250 megahertz this range is determined by antenna and circuit characteristics. The measurement system is demonstrated, and measured data from several different helicopters are presented in different forms. These different forms are needed to determine which of the resonant frequencies are real and which are false. The false frequencies are byproducts of Prony's algorithm.