Antenna systems that can include first and second radiators and an electromagnetic coupler disposed adjacent to the first and the second radiators. The radiators can be tunable to one or more frequencies. The electromagnetic coupler can be, for example, an inductive coupler or a capacitive coupler. One or more of the antenna systems can be configured to use carrier aggregation by tuning the first and/or the second radiators. For example, one or more of the antenna systems can be configured to use inter-band aggregation, intra-band contiguous aggregation, and intra-band non-contiguous aggregation.