Gain Improvement of Vivaldi MIMO Antenna With Pattern Diversity Using Bi-Axial Anisotropic Metasurface for Millimeter-Wave Band Application

In this letter, a high gain Vivaldi multi-input-multioutput (MIMO) antenna with orthogonal pattern diversity for millimeter-wave (mm-Wave) band application is proposed with the reduction paradigm towards nonuniform phase errors (at Vivaldi aperture) through metasurface loading. The nonuniform phase error limits the endfire gain (4.9-5.9 dBi) and hence the efficacy of the system. To compensate the phase error and improve the gain, a bi-axial anisotropic metasurface unit cells have been thoroughly investigated in systematic manner and strategically loaded at Vivaldi MIMO antenna. The endfire gain improvement with metasurface loading is reflected to be similar to 73% higher at 28 GHz with gain variation 8.2-10.2 dBi in the band of interest. Simultaneously, high pattern integrity behavior of the MIMO system is confirmed by the appreciable 1 dB gain bandwidth (33%). The standard port-to-port isolation (>15 dB) and MIMO performance parameters (ECC < 0.2 and TARC > 10 dB) confirms its suitability for mm-Wave band application.