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Simulating Radar Signatures of Electrically Large Targets in ANSYS HFSS

Designing for stealth involves reducing a platform’s radar cross section or RCS. Simply put, RCS represents a target’s ‘size’ as seen by a radar system. Stealth design seeks to minimize a platform’s radar size since the larger it is the more easily the platform can be detected. Some examples of stealth platforms include F-117 Nighthawk, F-22 Raptor, B-2 Spirit, and the F-35 Lightning II. These platforms possess unique, previously unconventional, shapes combined with radar absorbent materials designed with the goal to minimize a platform’s electromagnetic scattering characteristics, its RCS. Reducing this RCS, sometimes referred to as a radar “echo” or signature, makes them less visible to radar allowing them to advance undetected through defense systems.

Developing a stealth aircraft is challenging and can be a very costly endeavor especially in the prototyping stage where facility and testing costs can be considerable. Traditional simulation approaches on the other hand are either computationally expensive or require significant approximations to the results. However, with new techniques recently developed at ANSYS, engineers can use simulation tools like ANSYS HFSS and HFSS SBR+ to design an aircraft’s stealth characteristics in a computationally efficient and fast fashion while maintaining a high degree of accuracy in the results. All this can be done prior to the platform’s construction thus eliminating prototype cycles and reducing costs through minimizing test and measurement requirements.

There is a great demand for simulation tools to perform high-fidelity and efficient radar signature modeling of electrically large platforms. ANSYS HFSS, with the addition of the SBR+ solver, ushers in a modern era of fast and efficient large target RCS modeling in an advanced and easy-to-use interface compatible with both Windows and Linux operating systems. The advantage of using SBR+ solver over other traditional asymptotic techniques such as physical or geometrical optics is in the use of integrated and advanced diffraction physics based upon Physical Theory of Diffraction (PTD) and Uniform Theory of Diffraction (UTD) for capturing scattering effects from vehicles that contain sharp edges and abrupt surface discontinuities. Shooting and bouncing ray (pure SBR) enhanced with PTD and UTD in HFSS SBR+ allows accurate signature prediction for electrically large bodies composed of metals and dielectrics.

The software provides control over the level of physics to implement in a simulation allowing for upfront fast analysis with SBR with later addition of PTD and UTD correction if necessary for higher fidelity, more accurate, simulation results. In addition, with its integration into the parametric HFSS interface, design exploration and goal-driven optimization can be easily performed. For post processing, along with 2D and 3D RCS plots for both monostatic and bistatic RCS analysis, the data can be extracted and post-processed into more advanced formats such as for an inverse synthetic aperture radar (ISAR) study. This advanced capability, including outputs like range profiles, waterfall plots and ISAR, with both pre- and post-processing automation, is available with the installation of ANSYS Application Customization Toolkits (ACT) for radar analysis.

The use of stealth technology is not restricted to aircraft and missiles but also actively used in developing ground vehicles and combat ships. Simulation with HFSS and HFSS SBR+ can help navies in their quest to develop ships that possess small radar signatures and make them more survivable regardless of whether these ships are used for humanitarian or combat missions.

At the same time HFSS SBR+ can be used for antenna placement studies, a discipline that often combines with RCS analysis. The ANSYS hybrid solver technology allows for the utilization in HFSS SBR+ of localized sources from full-wave finite element (FEM) and/or method of moment (MoM) solutions. Here a detailed FEM model of an antenna element or antenna array can be leveraged to excite an HFSS SBR+ analysis of a complex antenna system mounted on an aircraft platform. All this allows for a broad dynamic range of geometric and material detailed to be analyzed in one rigorous electromagnetic simulation.


Learn more about ANSYS HFSS.