MIMO Mobile Handset Antenna Merging Characteristic Modes for Increased Bandwidth

The behavior of a mobile handset chassis-mode antenna with a metal bezel is analyzed in this paper by utilizing the theory of characteristic modes (TCM). Two eigenmodes, one from the chassis (0.5 lambda-dipole mode) and the other one from the bezel (1 lambda-perimeter mode), are merged by a monopole exciter to broaden the antenna bandwidth below 1 GHz. A new eigenmode from the bezel (1.5 lambda-perimeter mode) is also exploited to achieve multiple-input multiple-output (MIMO) performance. The characteristics of the antenna are verified with an experimental prototype and measurements. The measured input reflection bandwidths from the two ports are 263 MHz (742-1005 MHz) and 93 MHz (863-956 MHz), respectively. The port isolation is more than 7.4 dB across the whole band of interest. Finally, the monopole exciter, which excites two eigenmodes in the low-frequency band, is modified to provide more resonances in the upper frequency band, providing coverage in the range of 1715-2060 MHz and 2280-2710 MHz.