Features Study - A Study of RF External Transmissions

摘要

Cepstrum and Fast Fourier Transform techniques are developed which provide a theoretical basis for determining the configuration of aircraft and space vehicles. Some of the limiting assumptions of the analysis, and possible problem areas are discussed. The antenna radiation pattern of an omnidirectional antenna is largely determined by the shape, composition, location and size of the features of the vehicle to which the antenna is attached. The objective of this effort was to develop a method for determining the features and/or configuratiion of an aircraft or space vehicle from signals transmitted by those vehicles. A signal processing technique called Cepstral Processing offered the best chance to do this. Cepstral Processing is based on the fact that an RF signal sensed in the far field of the transmitting antenna will be a complex composite of the direct antenna signal path, and multipath reflections from vehicle wing suraces, landing gear struts, fuel pods, etc. This report documents two possible approaches for extracting required feature information from omnidirectional signals. The first approach is Time Signal Processing. The second approach Antenna Radiation Pattern Processing.