关键词: 伴随方程, 雷达吸波材料, 阻抗边界条件, 雷达散射截面, 梯度优化

Abstract: The development of anti-stealth technology has put forward higher requirements for the stealth performance of military aircraft. In response to the design problem of low radar cross section (RCS) of aircraft considering absorbing materials, combined with imped-ance boundary conditions, the discrete adjoint equation of Maxwell's equation considering absorbing materials is established. The multi-layer fast multipole expansion form of the adjoint equation is derived, achieving efficient RCS gradient calculation with re-spect to shape parameters, material electrical parameters, and coating thickness. A switch function is proposed to conduct absorbing material coating position optimization. Shape parameters, material coating position, coating thickness, and electromagnetic param-eters optimization based on the adjoint method using typical shapes such as the inlet. The design results indicate that gradient opti-mization based on adjoint equations can achieve cavity shape design considering the characteristics of absorbing materials, further reducing the scattering intensity of the cavity on the basis of ideal conductor shape design and material coating; Being able to opti-mize the design of material parameters and coating thickness, providing guidance for the selection and coating of absorbing materi-als; Optimization of coating position based on switch function can achieve optimal allocation of absorbing materials under the con-straint of total material weight. The proposed RCS adjoint optimization method for absorbing materials can provide reference and technical support for the design of efficient coating schemes for absorbing materials.

Key words: electromagnetic adjoint equation, radar absorbing material, impedance boundary condition, radar cross section, gradient optimiza-tion