Wanye Xu

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.

Surface Configuration Design of Cable-Network Reflectors Considering the Radiation Pattern

Since the curved surface of a cable-network reflector is generally approximated by regular flat facets, the electromagnetic performance of the cable-network reflector is determined by the size and shape of the facets. In many cases, the geometric approximation errors of the facets are periodically distributed on the surface, which can result in strong grating lobes. First, in this paper, the periodicity of the geometric approximation error and the effects of this periodicity on the EM performance are investigated. Second, the periodic geometric approximation errors of the regularly faceted configurations are disturbed by three proposed approaches, and three new types of surface configurations are thus formed. The first approach is to introduce radial direction disturbance parameters, the second one is to change the shape of the outlines and the last one is to use a Penrose-tiling-like configuration. The first two approaches are carried out in combination with the optimization strategies. Finally, the effects of the mentioned disturbance parameters on the EM performance are simulated, and some numerical examples are given to show that the surface configurations proposed in this paper can reduce the grating lobes level obviously, without either decreasing the gain or increasing the structural complexity of the cable-network reflectors.

Far-Field Pattern Tolerance Analysis of the Antenna-Radome System With the Material Thickness Error: An Interval Arithmetic Approach

As the geometry thickness error of composite radome impacts the electromagnetic (EM) performance of the antenna-radome system, a novel interval arithmetic analytic approach to the analysis of the effect on average power pattern of antenna-radome system with the thickness error in the composite radome-based is proposed. The thickness error of radome’s composite material is modeled as interval-valued errors. The link between the interval of thickness error and the interval power pattern along with some main EM characteristics (sidelobe level, peak power, and half-power beamwidth) expressed as intervals are efficiently constructed. Some comparisons with measured and simulated results reported in the state-of-the-art literature, experiment data and Monte Carlo (MC) method result serve as a way to validate the interval analysis (IA)-based method. Some numerical examples are reported to reveal the effect of the main geometric properties (i.e., location, size, width, and midpoint of the error interval) of the thickness error interval on power pattern. The obtained results show that the proposed IA-based approach offers tangible advantages and exhibits effectiveness versus some traditional statistical techniques (e.g., MC method).

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.

Power Pattern Tolerance Analysis of Radome With the Material Property Error Based on Interval Arithmetic

For the problem that the material property error of composite radome will impact the electromagnetic (EM) performance of the antenna-radome system, a novel analytic approach for the research of the effect on average power pattern of the antenna-radome system with the material property error (including permittivity and loss tangent) in the composite radome based on interval arithmetic is proposed. The material property errors of the radomes composite material are modeled as interval parameters. The relationship of the material property error interval, the power pattern interval, and some main EM characters (sidelobe level, peak power, and half-power beamwidth) intervals are researched by interval analysis (IA). Some valuable conclusions are revealed by four kinds of numerical examples. The property errors of different composite materials (skin and core) and components (joint and panel) of radomes are taken into account. The proposed IA-based approach has good prospect to be applied in antenna-radome engineering.

A New Interval Pattern Analysis Method of Array Antennas Based on Taylor Expansion

In this communication, a new Taylor expansion-based interval pattern analysis method is developed to predict the impact of the small excitation amplitude uncertainty on the radiated array pattern. The dependence problem of the classical interval arithmetic, which may lead to overestimation of performance intervals, is addressed in this communication. The proposed method approximates by approximating the antenna power values to the first order with respect to the uncertain amplitude. The new method is simpler and can produce more accurate bounds of the antenna pattern and the pattern features than the existing techniques. Several representative numerical examples are investigated to demonstrate the validity and efficiency of the proposed method.

Study of Stepped Amplitude Distribution Taper for Microwave Power Transmission for SSPS

A novel stepped amplitude distribution (SAD) taper for microwave power transmission for space solar power satellite is proposed in this paper. The SAD taper is described by the summation of the Heaviside step functions. Through optimizing the “height” and “radius” of each step of the descriptive function, the maximal beam collection efficiency (BCE) with and without constraints on the radiation levels can be obtained. A large set of numerical experiments on continuous apertures and discrete antenna arrays are carried out. The results show that the obtained BCEs can be close to or even higher than those of the 10-dB Gaussian ones, which shows the superiority of the method. In addition, only several kinds of amplifiers are required in this method, and therefore, the cost and complexity of the system can be greatly reduced.