UHF handset monopole antenna designed for SAR compliance

The specific absorption rate, SAR, has become an important design criterion for wireless devices. A portable must meet various SAR regulatory standards. As a result, antennas are designed not only to meet the required matched bandwidths and efficiencies or gains, but also to be such that the whole antenna-chassis configurations do not result in SAR levels exceeding the compliance limits in the bodies of users. Traditionally, SAR is tested after the complete portable device has been put together. The designs would have to go through a few iterations of modifications and measurements before the design is finalized, should the designs result in high SAR levels. While antenna design works have migrated from cut-and-measure to computer aided design, it is now possible to design an antenna to ensure SAR compliance, with the help of EM modelling. This paper describes the design of a quarter-wave monopole antenna for a portable radio operating in the UHF band. While this is not a unique design, it served to demonstrate the use of SAR prediction techniques.