A Self-Decoupled Ku-Band CP MIMO Antenna Using Asymmetrically Stepped Slotted Patches

This letter proposes a small self-decoupled circularly polarized (CP) multiple-input-multiple-output (MIMO) antenna working in the Ku band for satellite communication. Each radiating element consists of an asymmetrically stepped slotted patch, in which slot-induced perturbations excite two orthogonal characteristic modes with a quadrature phase relationship, as verified by characteristic mode analysis (CMA). This radiator-level design inherently reduces mutual coupling (MC) between neighboring elements while achieving CP radiation, without requiring additional decoupling or polarization control mechanisms. The proposed antenna attains an impedance bandwidth of 12-14.2 GHz (16.8%) and maintains a minimum inter-element isolation of 25 dB across the operating band. CP is achieved with an axial ratio (AR) bandwidth of 12.73-14.35 GHz. The antenna demonstrates a peak gain of 9.7 dBic and an average gain exceeding 7 dB. The proposed architecture provides a simple and effective solution for compact Ku-band MIMO systems, such as very small aperture terminals (VSAT) and satellite communication applications.