A mobile device at least includes a dielectric substrate, an antenna array, and a transceiver. The antenna array includes a first antenna, a second antenna, and a third antenna. The third antenna is disposed between the first and second antennas so as to reduce coupling between the first and second antennas. The first, second and third antennas are all embedded in the dielectric substrate and substantially arranged in a straight line. Each of the first and second antennas is a transmission antenna and the third antenna is a reception antenna, or each of the first and second antennas is a reception antenna and the third antenna is a transmission antenna. The transceiver is coupled to the antenna array and is configured to transmit or receive a signal.