A mobile device at least includes a dielectric substrate, an antenna array, and a transceiver. The antenna array at least includes a first antenna and a second antenna. The first and second antennas are both embedded in the dielectric substrate. The first and second antennas have different polarizations. The transceiver is coupled to the antenna array so as to transmit or receive a signal. The polarization of the antenna array may be dynamically adjusted by controlling a phase difference between the first antenna and the second antenna.