MIMO Antenna System with Wideband, High Isolation and Directional Radiation Characteristics By Using Multi-functional Neutralization Line

A novel neutralization line technique is proposed in this paper to improve port isolation, impedance bandwidth and radiation feature for dual-antenna system. T-shaped branch, rectangular metal strip and reserved gap form the neutralization line structure, which is directly connected to the common ground. Attribute to the weak coupling effect between the T-shaped branch and the antenna common ground, new resonance frequency and reverse current path for cancelling mutual coupling are generated. By changing the position of the antenna radiation element, the novel neutralization line still exhibits efficient decoupling effect. To verify the attractive properties of the neutralization line, the dual-antenna system is analyzed and fabricated. The measured results indicate that within a compact area of 0.52λ0 × 0.52λ0, the dual-antenna system achieves maximum isolation exceeding 50 dB. The introduction of the neutralization line provides an isolation enhancement of up to 30 dB. Additionally, within the operating bandwidth of 4.06-6.42 GHz, a peak gain of 4.4 dBi and radiation efficiency above 70% are obtained, both closely matching the simulated results. In addition, the excellent MIMO characteristics of ECC < 0.025, DG ≤ 10 dB and TARC < -10 dB demonstrate that the designed antenna is suitable for applications in N46, N47, N79, Wi-Fi and CV2X fields.