Quad-Element LTE Hidden Car Roof Antenna System

This letter presents the systematic design and optimization of a compact quad-element multiple-input–multiple-output (MIMO) antenna system in a roof cavity for the expected channel behavior at a 700 MHz LTE band. Beginning with a standard low-profile antenna element, the desired radiation pattern is synthesized by structural modification. The configuration for a quad-element design is then optimized. The results show that the proposed hidden solution even outperforms a nonhidden reference antenna of four quarter-wave monopoles in the cavity, making it attractive for real application.