Analysis And Control Of Radar Cross-section From Antennas, Frequency-selective Surfaces And Conducting Plates

Radar, as a chief kind of equipment for the detection and location of objects, has found wide applications in modern military operations. Thus the radar stealth performance of friendly military systems and platforms acts as a vital measure of their survivability in hostilities. The radar stealth of friendly objects obtained through properly designing can help them effectively avoid the incoming threats generated by hostile radars. As a result, the hostile radar detection of friendly objects can be delayed and the combat capability of hostile radar systems can be weakened. The survivability of friendly objects can then be improved.The radar stealth or radar low observability has been usually achieved through reducing the radar cross-section. Shaping and radar absorbing materials, as two radar stealth techniques that have been relatively well developed and extensively applied, can properly reduce the radar cross-section from military platforms. However, certain components and subsystems installed on modern military stealth platforms have been theorectically or experimentally classified as dominant scattering sources of those platforms, such as the antenna system which may contain the antenna and radome. Dominant scattering sources can generate strong radar echo, which tends to be a threat to the stealth performance of the whole platform. Meanwhile, due to operating characteristics of those components and subsystems, the simply direct use of traditional radar cross-section reduction techniques may affect their operating performances.In order to improve the radar stealth of the whole platform, radar cross-section reduction design of components exhibiting strong radar cross-section is of practical significance. On the other hand, due to the widely used electromagnetic detection, radar decoy is showing its special importance in the improvement of survivability of friendly real units and platforms. Therefore, radar cross-section enhancement design of specific radar targets is also of practical significance. This dissertation presents radar cross-section reduction designs of antennas, frequency-selective surfaces and conducting plates. Radar cross-section enhancement designs of conducting plates are also presented. The contents are divided into following parts.Chapter 1 contains the background information and significance of radar cross-section control, describes the research status of radar cross-section reduction of antennas, frequency-selective surfaces and conducting plates, the research status of radar cross-section enhancement is also presented.Chapter 2 introduces the antenna polarimetric total scattering matrix based on the equivalent description of antennas or arrays with multiple feeding ports, discusses in detail the polarimetric total scattering matrix for antennas with one or two feeding ports.Chapter 3 proposes a novel technique based on PIN attenuator diodes to reduce the backscattering from a microstrip patch antenna and its array, presents a complex ground including frequency-selective surface cells for backscattering reduction of a microstrip patch antenna, introduces the termination impedance for cancellation between the antenna mode and structural mode scattering and uses it to reduce the backscattering from dielectric resonator antennas, proposes a planar bilayer four-arm spiral antenna and a resistor-loaded planar two-arm Archimedean spiral antenna with reduced co-polarization backscattering.Chapter 4 introduces rasorber designs which can reduce the reflection from rejection bands of two-dimensional frequency-selective surfaces and can retain the transmission window with small insertion loss, based on the equivalent circuit model. The reflection reduction helps backscattering reduction and radar stealth improvement.Chapter 5 studies the non-magnetic single-layer circuit analog absorber based on its equivalent citcuit model. Using the double-square-loop as the unit cell structure, a design with three resonances observed within the absorption band is proposed. Optimum performances of the non-magnetic single-layer circuit analog absorber can then be obtained. Four resonances are observed through the use of a high-impedance surface. The wideband absorption indicates a wideband reduction of backscattering from conducting plates. Besides, a wideband parallel-plate waveguide is designed to retrive the reflection coefficient from a one-dimensional wideband absorber prototype.Chapter 6 introduces the backscattering characteristics of thin conducting plates, proposes a quasi-superdirective reradiation-based backscattering enhancement design of thin conducting plates at edge-on incidence.Chapter 7 summarizes this dissertation and lists some work that may be topics of future studies.