For a mobile terminal (for example, a mobile phone), when an uplink rate and/or a downlink rate needs to be improved, it may be implemented by increasing a bandwidth. An increase in a bandwidth may be implemented by using carrier aggregation (CA), which specifically includes the following two types: a first type, carrier aggregation within a frequency band; a second type, carrier aggregation in different frequency bands. For the first solution for increasing a bandwidth, a radio-frequency signal may be received by using a primary antenna, and different I/Q (in-phase/quadrature) demodulation is performed on the received radio-frequency signal. For the second solution for increasing a bandwidth, in the prior art, because radio frequency resources actually used in mobile communications are relatively scattered, bandwidths of some frequency bands used in mobile communications are relatively narrow, and the like, when carrier aggregation is performed in different frequency bands, an independent antenna needs to be added for each frequency band, to perform corresponding receiving/sending.
FIG. 1 shows a schematic diagram of an antenna included in a currently common mobile terminal, and to exemplarily show antennas, the antennas are marked by using dashed lines. As shown in the figure, the system includes a primary antenna 1, another primary antenna 2, a diversity antenna 3, and a parasitic antenna 4, where the diversity antenna 3 is used to resist weakness, and the parasitic antenna 4 is used to spread a spectrum. To meet a requirement of carrier aggregation performed in multiple frequency bands, the primary antenna 1 may be used for one frequency band, and the another primary antenna 2 may be used for another frequency band. It can be seen from the figure that the terminal has already included multiple antennas, and moreover, because mobile terminals are increasingly miniaturized, it is extremely difficult to add an antenna within limited space of the mobile terminals.