Airborne High-power Broadband Antenna Radiation Characteristics

With rapid development of science and technology and wide applications of airborne electronic equipments, a large number of antennae and electronic equipments are often installed in a limited space such as an aircraft. Also, the aircraft is a complicated electromagnetism scatter. Thus, the electronic equipments and the aircraft may result in the change of the radiant characteristics of antennae. So, it is very important in the engineering applications for the antennae to analyze accurately the radiant characteristics scattered by the aircraft. Moreover, the analysis brings some reference value and great significance to the optimal layout of airborne antennae and prediction of electromagnetic compatibility (EMC).In this dissertation, the eigenvalue and field distribution of double-ridged waveguides, field distribution of the mouth of double- ridged horn antenna, direction graph of far field and the effect of radiant characteristics scattered from the aircraft are studied. Main contents of this dissertation are as follows.1. The cut-off wavenumber and latent mode of ridged waveguides are analyzed contrastively using transverse mode-matching method(TM3) and finite element method (FEM). Principal mode of double-ridged waveguides, and the cut-off wavenumber and field distribution of high-order mode are studied in details. The main points of TM3 are that latent mode field is expressed with series and the deduced process is very clear, while the characteristics of FEM lie in that the effect of high order mode and the continuity of the distribution field are considered.2. Strictly and accurately theoretic analysis of ridged horn antenna cannot be made because of the effect of the ridge. So, a hybrid approach combined by FEM and lengthways mode match method is presented to analyze the whole ridged horn. The detailed algorithm is given. S parameter matrix is achieved, i.e. the ratios of the modes of the caliber field.3. After the ratios of the modes of the caliber field are obtained, far field radiate direction graph of multi-mode-arbitrary polarization is solved using pattern-expanding method and mouth-plane integral method when the horn antenna is an arbitrary space.4.UTD is employed to analyze the effect of the aircraft on radiant characteristics of the antenna on the aircraft. Because ray-racing technique is an important part of analyzing the scattering effect of the aircraft on the antenna, this dissertation studies the ray-tracing technique in detail. The algorithm of the ray-tracing technique is described and the electrical field strength of each ray is calculated. Then, all of the field strength is analyzed using vector-method and the radiating characteristics of the airborne antenna are obtained.When studying the radiating characteristics of the airborne antenna in this dissertation, the radiating characteristics in the light area are analyzed emphatically. The results achieved in this dissertation have good guidance significance to analyze the radiating characteristics of the antennae installed in some electronic-large-size carriers, such as naval vessels, airplanes and guided missiles, and to design the mutual coupling and EMC among antennae in some carriers.