Sub-6 GHz band massive MIMO antenna system for variable deployment scenarios in 5G base stations

A compact massive multi input multi output (MIMO) antenna system with 1 x 4 (sector) subarray configuration operating at sub-6 GHz range for 5th generation (5G) base stations has been designed and analysed in various geometries (rectangular, triangular, and hexagonal). The capacity of the system can be increased by more than 10 times whereas the energy efficiency can be increased 100 times using the massive MIMO system (Larsson et al. in IEEE Commun Mag 52(2):186-195, 2014). A maximum of 5 sectors has been used, with each sector comprising of 1 x 4 subarray elements. Each sector consists of three layers, in which 1 x 4 patches are located on its top layer whereas it's feeding network and ground plane are placed at the bottom layer and middle layer respectively. The entire system can operate in two modes, individual port operation and massive MIMO array operation with beam steering capabilities. The measured bandwidth of the system is 140 MHz that covers the frequencies from 3.36 to 3.50 GHz in sub-6 GHz band. The overall dimension of a unit subarray in terms of length, width and height is 280.5 x 56.1 x 2 mm(3). The gain of an individual port is found to be 12.77 dBi and the overall gain of a single panel with 5 sectors arranged in rectangular form is 19.73 dBi. Mutual coupling among all the ports has been kept less than - 16 dB. The operating frequency range of the antenna array system is chosen in the range of 3.3-3.8 GHz, as this band has been allocated and targeted across the globe to enable 5G in Sub-6 GHz band.