الفهرس | Only 14 pages are availabe for public view |
Abstract Intensive review on the electrical and structural aspects of airborne antennas in different frequency bands (excluding microwave bend) revealed the special importance of the frequency range 100-1000 MHZ to the various applications. This review revealed also that the majority of the externally mounted antennas in this frequency range comprise one or more monopole structures. Due to the numerous impedance matching techniques in this frequency range, the major part of the problem of monopoles on airframes is the determination of their radiation patterns. In this research work the problems of radiation from V.H.F. and U.H.F. airborne antennas on different airframes are studied on modeled shapes for these airframes. The modeled shapes are simpler in geometry than the original airframes but, nevertheless retain their general features. Thus cylindrical fuselages of aircrafts, conical airframes of spacecraft’s and moderate size missiles are modeled into cylinders, frustums of cones and composites of cylinders and conical parts respectively. Many investigators handled the problem of radiation from a current element near an infinite conducting cylinder while, due to the theoretical difficulties encountered, only few investigators examined the case of finite cylinder. Recently theoretical numerical techniques have been used in the solution of electromagnetic field problems. These techniques depend on the face that with the aid of high speed computers it is often more convenient to use methods which are analytically simple but require large amounts of computations. |