Smarter, faster design of metasurfaces that scatter radar waves

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The fabricated coding metasurface (left) next to a plain metal reference plate of the same size (right).
The fabricated coding metasurface (left) next to a plain metal reference plate of the same size (right).
The “spiralling cross” unit cell in its two states, “0” and “1”
The “spiralling cross” unit cell in its two states, “0” and “1”: a small change in geometry gives the 180° phase difference needed for coding.
Measurement set-up
Measurement set-up: simulated scheme (a) and the bistatic system in the anechoic chamber (b).
Simulated and measured scattering maps for the reference plate and for the metasurface
Simulated and measured scattering maps for the reference plate and for the metasurface: the metasurface spreads the reflected energy over many angles.
The optimized coding pattern and the resulting scattering at 8, 10 and 12 GHz
The optimized coding pattern and the resulting scattering at 8, 10 and 12 GHz: instead of a strong back-reflection, the energy is scattered in many directions.

Reducing the radar cross-section (RCS), that is how “visible” an object is to radar, matters for aircraft, ships, drones and satellites, but also for civil and dual-use systems. Coding metasurfaces, flat panels made of tiny cells that reflect with a phase of 0° or 180°, can scatter radar waves in many directions instead of back to the radar. Designing them is demanding, however: finding the best arrangement of cells requires many slow full-wave simulations.

What is new

  • A hybrid genetic algorithm in two stages: a fast analytical pre-optimization (Huygens–Fresnel principle) followed by refinement with full-wave simulations.
  • A new “spiralling cross” unit cell, whose meandered delay lines give extra freedom to tune the response and support intermediate phase states beyond the classic 1-bit scheme.

Key results

  • The hybrid approach cuts computation time by about 25% compared with full-wave-only optimization, with comparable performance.
  • It avoids the trivial checkerboard layouts produced by purely analytical design, which ignores coupling between cells.
  • The optimized metasurface reaches a maximum RCS reduction of about 21 dB near 10 GHz and about 12 dB on average over 9–12 GHz.
  • A prototype was fabricated in our lab and measured in an anechoic chamber, in good agreement with simulations.

Impact & outlook

The method strikes a good balance between accuracy and computational cost and scales to much larger metasurfaces. Next steps include multi-bit coding, which could widen the bandwidth and lead to programmable metasurfaces for stealth, electromagnetic compatibility and wireless applications.

Reference: S. Marzullo, I. Marasco, A. D’Orazio, G. Magno, “Hybrid Genetic Optimization of Metasurfaces for Scattering Control: X-Band Design and Experimental Validation,” Progress In Electromagnetics Research 185, 97–109 (2026). doi:10.2528/PIER26021001