Review of antenna design options for dual mode handsets

As mobile communications grow rapidly new frequency bands are being used. At the same time the mobile service providers are trying to equip end users with new terminals which bring additional benefits from operating at more than one frequency band. First commercial hand held portable terminals that can operate at two bands have also appeared on the market. Nevertheless the design of dual band handset antennas still presents a challenge for both antenna design engineers and antenna manufacturers. This paper, hence, reviews the current state of the dual band antenna designs. In general, relatively simple dual band handset antennas can be divided into single feed and dual feed structures, whereas more complicated solutions are based on adaptive array techniques. The review begins with description of dual feed antennas. Most frequently used external antennas i.e., monopoles and helices are considered first. This is followed by an introduction of a planar inverted-F antenna (PIFA) as a typical internal (integral) antenna. A retractable multi-element antenna is mentioned next. Single feed composite antenna structures, both external and internal are also considered and the review is finished with a discussion of adaptive arrays as handset antennas. At the end two examples of commercially available dual band antennas are presented.