On near-field radiation characteristics of the internal handset antenna with a curved metal pattern

Near-field radiation characteristics of the internal handset antenna with a curved metal pattern are studied in this paper. We demonstrate that by using a smoothly curved metal pattern for an internal cellular handset antenna, the specific absorption rate (SAR) can be decreased, compared to a corresponding antenna with a metal pattern having right-angle or abrupt bendings. Results for a simple strip monopole for the GSM1800/1900 operation in the handset are presented and discussed. Related results obtained for corresponding strip monopoles with a right-angle bending or multiple-bendings are shown for comparison. The reason for decreased near-field radiation is because the excited surface currents on the strip monopole with a curved bending will experience a smooth variation on the surface current trace on the metal pattern of the antenna. On the other hand, the excited surface currents on the corresponding strip monopoles will experience relatively abrupt changes on the surface current trace of the antenna's metal pattern, which will result in strong near-field electric fields. It can be expected that the abrupt variations of the excited surface currents on the metal pattern of the antenna will cause sharp increase in the near-field radiation of the antenna. This behavior will lead to increased SAR values [1] and HAC (hearing-aid compatibility) values [2, 3] as well for the handset with such an antenna embedded therein.