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06-07-2022 | Posted by Joaquín Martí
Airborne radomes (radar domes) are critical for protecting the antenna from the environment. However, the radome can affect the performance of the antenna systems, which makes it essential to consider the radome while designing the antenna system. A well-designed radome is transparent to the electromagnetic waves within the operating frequency band of the antenna while satisfying the structural and aerodynamic requirements.
In a paper presented at the NAFEMS World Congress 2021, the electromagnetic performance and the mechanical response of the radome are considered simultaneously while optimizing the material properties and geometrical parameters of its wall structure. Aerodynamic forces on the radome surface are extracted from a steady-state Reynolds Averaged Navier-Stokes (RANS) fluid dynamics analysis and mapped onto the structural model. The structural integrity of the radome is simulated by applying the aerodynamic pressure from the CFD analysis in linear static and buckling analyses. Additionally, an explicit bird strike analysis is performed using smoothed particle hydrodynamics (SPH) to prevent structural failure in bird strike events. A hybrid simulation approach is utilized to model the electromagnetic interaction between the antenna system and the radome based on a 3D full-wave analysis technique as well as Physical Optics.
To validate the design approach a multi-layered sandwich radome, protecting a weather radar antenna operating at X-band (9.3 GHz), is studied in the paper. The antenna and the radome are situated at the nose of a regional jet commercial aircraft. A slotted waveguide antenna array is used to achieve the scanning behaviour. The aerodynamic forces on the radome surface are computed at typical cruise flight conditions to provide the input for calculating the resulting stress under the aerodynamic loading. The thickness and the stacking sequences of the different layers of the radome are optimized to maximize the transmission coefficient, constrained by the buckling safety factor. Additionally, the maximum structural damage in the event of a high-velocity bird impact is simulated to ensure the structural integrity of the radome with the optimal design parameters. The lightning protection strips on the radome are included in the study to investigate the impact of the solid and segmented strips on the radiation performance of the antenna.
This approach offers an efficient workflow to automate the multiphysics analysis of the radome, resulting in optimal designs for its electromagnetic and mechanical performance. It enables early-stage validation of the radome design and an accurate prediction of the antenna behaviour, thus reducing physical prototyping and therefore design costs.
The analysis could be extended to study radomes on aircrafts flying at higher speeds or on missiles, which experience higher temperatures due to the aerodynamic loading. This affects the electromagnetic material properties of the radome, thus requiring a strong coupling of the electromagnetic and computational fluid dynamic analyses along with the structural analysis of the radome.