Equivalent circuit of a two-element spherical small antenna

摘要

For convenient portability mobile devices need to be small. To reduce their size, a small antenna is strongly required because the antenna is one of a mobile device's largest components. In addition, the antenna's bandwidth needs to be wide because the recent development of many kinds of multimedia services requires a large bandwidth. Designing a small antenna with a wide bandwidth is not easy, however, because an antenna's bandwidth is inversely proportional to the antenna's radiation Q-factor, the lower bound of which is determined by the radius of the virtual sphere, which includes the antenna's whole structure.