Compact wideband X-band MIMO antenna with enhanced isolation using neutralization line and modified ground structure

A compact two-port MIMO antenna is proposed for X-band wireless and radar applications where limited installation space is a key constraint. The antenna is fabricated on a low-cost FR-4 substrate and occupies only \(16 \times 18 \times 0.8~\textrm{mm}^3\) . By optimizing the radiator geometry together with the partial ground plane, an impedance bandwidth of 8–12.5 GHz is obtained. Mutual coupling between the two radiating elements is reduced by integrating a neutralization line with rectangular slots in the ground plane. The neutralization line introduces a controlled coupling path between the elements, while the ground slots alter the surface-current distribution and contribute to isolation enhancement. The antenna provides more than 20 dB isolation over most of the operating band and maintains stable radiation characteristics, with simulated radiation efficiency exceeding 92% over the favorable portion of the band. The MIMO characteristics are further evaluated using ECC, diversity gain, MEG, and TARC, with an ECC below 0.001 and diversity gain close to 10 dB. A fabricated prototype is characterized experimentally, and the measured S-parameters and radiation characteristics exhibit reasonable concordance with the simulated outcomes. The obtained results demonstrate the feasibility of the proposed compact configuration for X-band MIMO applications.