Research On Three-dimensional Wideband Microwave Absorber And Its Energy Protection Application

Microwave Absorbers(MA)are a class of periodic structures that absorb the incident electromagnetic waves within their operating bands.They are widely used in many electronic systems to improve their electromagnetic compatibility(EMC)or reduce the radar cross section(RCS).In this thesis,a new kind of three-dimensional(3D)microwave absorber based on coupled-slotline structures has been proposed to realize wideband absorption.Moreover,an energy selective structure(ESS)has been proposed based on a 3D Band-notched absorber.The main contents of this thesis are as follows:1?Two kinds of three-dimensional microwave absorbers based on coupled-slotline structures have been proposed.The operating principle of electromagnetic absorption was analyzed by the current distribution on the metallic surface of the structure and the transmission line theory.The input impedance was matched to the free space wave impedance by optimizing the structure,and a wide absorption band was finally realized.First,single-polarized microwave absorber based on the coupled-slotline structure produced an absorption band from 3.7GHz to 5.9GHz with absorption rate more than 90%.Second,a dual-polarized wideband microwave absorber with wider absorbing bandwidth and better angular stability was proposed.The dual-polarized design is more practical in various applications.Measured results showed that the wideband microwave absorber can achieve122.7% fractional bandwidth.2?The working mechanism of each component of an ESS was studied.The working states of PIN diode under open-and short-circuit conditions were obtained through simulation analysis.The spice model of the diode can well explain the working mechanism in space field environment.The approximate values of equivalent capacitance and equivalent inductance of metal wire under different spatial field conditions are obtained by theoretical calculation and analysis.In order to reduce the energy loss of the incident electromagnetic wave passing through the energy selective surface,two solutions are proposed.3?A wideband microwave absorber with energy selection characteristic was studied and designed.The improved design of absorber 2 can control the absorber 1 and absorber 2 to work together under the condition of high power electromagnetic wave incidence and completely absorb the incident wave.However,under the condition of low power electromagnetic wave incidence,only absorber 1 works,and the in-band incident wave is completely reflected and absorbed out of band to reduce the out-of-band RCS.Two solutions proposed in this paper are used to optimize the energy loss under low power electromagnetic wave incidence,and the corresponding relationship between different oblique incidence angles and starting threshold is studied.