A Dual-Polarized Wideband Phased Array With Enhanced Low-Scattering Characteristics Enabled by Unbalanced Coupling Structures

An X-band dual-polarized phased array with in-band co-polarization low-scattering property is presented. Unlike previous works, the relationship between mutual coupling and in-band scattering is investigated, identifying that the coupling structure is one of the primary contributors to residual mode scattering. Taking advantage of this feature, the bridge circuit topology is employed to analyze the effects of unbalanced adjustments for the coupling structure, revealing that these adjustments will lead to polarization conversion of the scattered field from co-polarized to cross-polarized form. Subsequently, a p-i-n diode-based central branch with interpolarization coupling current control ability is introduced for the real-time control of the trade-off between scattering and radiation performance. As a result, a dual-polarized element and its mirror element co-designed with controllable scattering polarization conversion ability are proposed, enabling residual mode scattering cancellation when arrayed together. As a demonstration, a prototype is fabricated and measured, which is capable of operating from 7.6 to 12 GHz with a radiation beam scanning up to ±60° in E-/H-plane. The achieved in-band co-polarized monostatic radar cross section reduction (RCSR) averages 16.5 and 21.4 dB for H-/V-polarized incidence, respectively. The measured results align well with the simulation results, thus confirming the good performance of the proposed array.