Passive Structural Cancellation Technique for UWB PAA Copolarized In-Band RCS Reduction via Stepped-Impedance Metasurfaces

This letter proposes a novel passive structural cancellation (PSC) technique achieving co-polarized in-band radar cross section (RCS) reduction for ultra-wideband (UWB) phased array antennas (PAAs), by engineering the scattering fields of 3D stepped-impedance metasurfaces (SI-MS) to destructively interfere with the residual scattering fields of a reference PAA. Simulations extract the reflection parameters of reference elements to define the required SI-MS unit quantity and phase response for perfect PSC. Following SI-MS unit topology optimization, experimental validation demonstrates its effectiveness: A fabricated 8×8-element all-metallic stepped notch array integrated with a 2×8-unit SI-MS radiates effectively within 2.5-10.9 GHz and achieves ±45° beam scanning. The proposed array achieves significant co-polarized in-band RCS reduction across 3.9-9.6 GHz exceed 7 dB. The PSC approach resolves the long-standing challenge of in-band RCS reduction without compromising radiation performance in UWB PAAs, overcoming inherent limitations of active cancellation technique.