Improving the RF Performance of Clamshell Handsets

The designers of handsets for mobile radio networks are subject to pressures to integrate more and more functionality into handsets whose dimensions, led by the expectations of the market, shrink with each new generation of designs. This pressure is accentuated by the demand for power created by large colour displays and cameras, while the dimensions available for batteries are stringently limited. On examining the link budget for a mobile radio system it is very obvious that the low gain of a typical handset antenna is an area capable of significant improvement. For the network operator the modest RF performance of handsets limits their coverage, while for the user it not only degrades the service they enjoy, but also significantly diminishes battery life (talk time). This article discusses the important interactions between aspects of the design of the handset and the RF performance which can be obtained from it. As will be seen, acceptable RF performance is not just a matter for the antenna designer, but depends on an understanding of the underlying issues on the part of the whole handset design team.