Theoretic Study of Antenna Scattering Problems Based on Characteristic Modes and its Applications in Reducing Antenna Scattering

Abstract

A new antenna scattering theory based on characteristic modes (AST-CMs) is proposed to analyze the antenna scattering mechanism and guide the design of antenna scattering reduction in this article. A specific set of modal electric fields, which of an antenna loaded with a short circuit, is used to express the structure mode and antenna mode scattering fields of the antenna with arbitrary loads. The contribution of each characteristic mode to the structure mode and antenna mode scattering fields can be clearly analyzed, which efficiently guides the antenna scattering reduction under the incident plane waves with arbitrary propagation direction and polarization. A typical microstrip antenna is given as an example to validate the proposed AST-CM. The radar cross section (RCS) of the microstrip antenna calculated by AST-CM agrees well with the result simulated by commercial simulation software Altair FEKO. Moreover, the design procedure based on AST-CM is used to guide the in- band RCS reduction of the microstrip antenna under both <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x}$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${y}$ </tex-math></inline-formula> -polarized normally incident plane waves. Compared with the reference antenna, the proposed antenna achieves a notable RCS reduction in its operation band with the radiation performance well preserved. The proposed low-RCS antenna is fabricated and measured, and the experimental results are in good agreement with the numerical simulated results.