A Dual-Polarized Multi-Sector Antenna Using Dielectric Image Lines for Millimeter-Wave Indoor Base Stations

A new dual-polarized multi-sector antenna for a millimeter-wave indoor base station (27.4-27.8 GHz) is presented. The proposed antenna consists of six horizontally polarized (H-pol.) and vertically polarized (V-pol.) end-fire antennas on a ground plane. Since reflection coefficients of the ground plane are anti-phased between H-and V-pol. antennas, conventional antenna designs suffer from significant deviations of the directivity and beam tilt, resulting in a problem of unmatched coverage area. The impact is theoretically clarified, and optimally shaped dielectric image lines (DILs) with orthogonal polarization (E11y and E11z modes) are introduced to realize the identical antenna patterns. The designed DIL antennas are then applied to the multi-sector antenna, offering a high gain of as much as 15 dBi, relatively low profile (0.46λ), polarization diversity, and matched coverage area in full azimuth angles. The measurement result confirms that the prototype has a 14.2 and 15.2 dBi directivity for H-and V-pol. antenna unit on average, and the beam tilt error is less than 1∘. The proposed antenna is suitable for millimeter-wave micro base-station systems, especially for a ceiling antenna and multiple-input multiple-output applications.