Evaluation of cellular phone antennas and the advantages of using internal antennas

Antennas for cellular phones are required to be small in size and light in weight. Since cellular phones are randomly orientated by their operators, their antennas have to be sensitive to both vertically and horizontally polarized waves and their radiation patterns should be quasi-isotropic. However, cellular phones usually operate while they are hand-held beside the human head. Thus, their antennas are required to fulfil such requirements beside the human body as well as in free space.