Yuanying Qiu

Multiobjective Particle Swarm Optimization of Boresight Error and Transmission Loss for Airborne Radomes

The streamlined shapes of airborne radomes tend to cause severe degradation of the electromagnetic (EM) performance, which could be compensated by properly designing the thickness profile of the radome. Boresight error (BSE) and transmission loss (TL) are the two most important EM characteristics that need to be improved. Previous researches focused on the single-objective optimization of either BSE, or the linear combination of BSE and TL through the conventional weighted aggregation (CWA) method. However, the single-objective optimization is limited in reaching mutual balance between BSE and TL, and could not explain why the optimal solution obtained by optimizing BSE usually has a better TL than the constant thickness radomes. In this communication, the multiobjective particle swarm optimization (MOPSO) combined with 3-D ray-tracing method is employed to optimize the BSE and TL simultaneously for airborne radomes. The simulation results explain why the optimal solution on BSE usually has a better TL; the TL wall phenomenon in the multiobjective space is also explained. Both problems are due to the variation of mean incident angle of the radomes during antenna scanning, which is general for streamlined radomes. Significant conclusions are drawn and could benefit the radome design in engineering applications.

EM Analysis of Deformed Metal Space Frame Radome

The presence of radome inevitably degrades the electromagnetic (EM) performance of the enclosed antenna while the deformation of the radome may make the degradations even worse. This letter studies the effect of structural deformation of a metal space frame (MSF) radome on EM performance. Far field of the antenna-radome system is obtained by adding the far field transmitted through skin to the scattered field of elements, both fields varying when deformation occurs. A 20-m MSF radome is employed for simulation, whose structural deformation under wind and self-weight is analyzed using finite element method (FEM). Several significative characteristics about the effect of deformation on EM performance are pointed out.

EM Performance Analysis of Radomes With Material Properties Errors

Modern radomes are commonly made of composites, whose material properties inevitably have errors due to the complicated manufacturing process, thus degrading the electromagnetic (EM) performance of radomes. In this letter, both systematic and random material properties errors are introduced in the EM analysis of radomes. A statistical method is proposed, which relates the random material properties errors to the EM performance of radomes. The tolerance of material properties, including relative permittivity and loss tangent, are determined from experiment. Several significative characteristics about the effect of material properties errors on EM performance are provided. Then, the compensation method through modifying the geometrical thickness is applied to improve the EM performance of radomes with material properties errors, which is proved to be effective.

Study on the Electromagnetic Performance of Inhomogeneous Radomes for Airborne Applications—Part I: Characteristics of Phase Distortion and Boresight Error

Inhomogeneous radomes, characterized by stacked layers of continuously varying dielectric parameters, are potential in yielding excellent electromagnetic (EM) performance. This two-part sequence of papers presents a study on the EM performance of inhomogeneous airborne radomes based on impedance match, including comparison with the conventional constant thickness radomes and variable thickness radomes (VTRs). In this paper, study on the phase distortion of antenna aperture field caused by inhomogeneous radomes gives a physical insight into the cause of radome boresight error (BSE), and explains why the substantial decrease of insertion phase delay (IPD) of inhomogeneous radomes, instead of leading to BSE improvement, increases the BSE. Based on the study, a method is proposed to estimate the IPD distribution which can be used to predict the BSE. The results reveal the EM characteristics of inhomogeneous radomes which is potential in realizing high-performance airborne radomes superior to traditional VTRs. The second part of the paper studies the bandwidth performance and the effect of radome coating, thickness errors, and layer number in order to acquire an overall understanding of the performance of inhomogeneous radomes.

Study on the Electromagnetic Performance of Inhomogeneous Radomes for Airborne Applications—Part II: the Overall Comparison With Variable Thickness Radomes

In the first part of a two-paper sequence, the phase distortion caused by inhomogeneous radomes is studied to reveal the boresight error (BSE) characteristics, and a method is proposed to estimate the insertion phase delay distribution and the BSE. In this second part, the bandwidth performance and the effect of radome coating, thickness errors, and layer number are further analyzed to acquire an overall understanding of the performance of inhomogeneous radomes through the comparison with variable thickness radomes (VTRs). Transmission loss and BSE, the two most important EM characteristics of airborne radomes, are considered. The bandwidth performance of VTRs is, from the authors’ best knowledge, for the first time optimized, and corresponding conclusions are drawn. Results indicate that inhomogeneous radomes have superiorities over VTRs, which makes this kind of radome a potentially popular choice in modern airborne applications.

A New Efficient Thickness Profile Design Method for Streamlined Airborne Radomes

The streamlined shapes of airborne radomes tend to cause severe degradation of the electromagnetic (EM) performance, which can be compensated by properly designing the radome thickness profile. Conventional variable thickness radomes based on optimization method yield excellent EM performance at the expense of 1) considerable design time consumed by the inevitable optimization process and 2) potential manufacturing difficulties as thickness profile tends to vary dramatically in the entire range of the radome. In this communication, we present an efficient thickness profile design method through introducing the concept of half-wave thickness under average incident angle. No optimization process is involved and gentle thickness profile variation is naturally guaranteed by the gradual variation of radome shape which determines the average incident angle. Both 2-D and 3-D cases are considered in computing the average incident angle. Results of a tangent-ogival airborne radome validate the effectiveness of the proposed method.