A low-profile dual-polarized directional antenna for an indoor MIMO transmission

Large channel capacity is achieved by Multi-Input Multi-Output (MIMO) technology with multi-antenna at the transmitter and receiver side, and many studies to maximize the channel capacity have been performed [1], [2]. In indoor wireless communications for small area as typified by femtocell and wireless LAN, the channel capacity has been reported to be enhanced by directional antennas and multi-polarization [3], [4]. In the above environment, Base Station (BS) is often placed at the ceiling due to realize a Line-Of-Sight (LOS) environment to Mobile Terminal (MT). We focused on the BS antenna for downlink transmission, and demonstrated that directive radiation patterns with a tilt angle in the downward direction are effective for enhancing the SNR and channel capacity, compared to sleeve antennas configuration [5].