Wireless communication system with multi-mode cavity antennas

An antenna system for implementation in a wireless communication system such as a mobile device, and a wireless communication system employing such an antenna system, and a related methodology, are disclosed herein. In one example embodiment, a mobile device includes a display, a chassis, and one or more electrical components. The display is provided along a front surface of the mobile device, and the chassis has first and second cavities provided along a rear surface of the mobile device, the rear surface being substantially opposite the front surface. Further, the one or more electrical components is or are supported in between the display and the chassis, and the one or more electrical components provide excitation signals to one or both of the first and second cavities so as to cause electrical fields in accordance with a plurality of modes to occur respectively within the cavities at multiple frequencies, respectively.