High Gain Narrow Beam MIMO Array Antenna Operating at n260 Band for Millimeter Wave Applications

This paper introduces a novel four-port antenna array designed for n260 band operation, specifically addressing challenges like path loss fading and multipath effects commonly encountered in millimeter-wave frequencies in urban settings. The proposed 4 ×4 MIMO antenna array operates in the n260 band, offering high gain and a narrow beam, with an extended design enabling spatial and pattern diversity to mitigate multipath effects effectively. The single-element antenna combines elliptical and circular rings fed by a quarter-wave transformer. Its fundamental frequency of 30 GHz is suppressed by integrating circular rings in the radiator and a slot in the ground plane, which enhances its first harmonic at 38.5 GHz while generating vertical polarization. The array antenna improves the fractional bandwidth (FB) to 8.4%, with a frequency range of 36.76-39.92 GHz, and achieves dual broadside beams at ±37° angles with a gain of 16.7 dBi. Additionally, it exhibits exceptionally low cross-polarization (-80 dB), minimizing cross-talk effects. The MIMO configuration demonstrates excellent isolation (|S21| > 26 dB and 31.2 dB) while maintaining similar FB and radiation pattern characteristics as the array antenna. This robust design, incorporating both spatial and pattern diversity, makes it highly suitable for 5G wireless applications.