Estimation and reduction of power absorbed in head from handheld terminals

Some of the radio frequency power transmitted from typical handheld terminals is absorbed in the head. This power loss is a drain on the communications link budget which translates to reduced battery time, and also carries a perception that there could be biological ramifications. The presence of the head affects the impedance seen at the antenna port, and this effect is known to be sensitive to the geometric details and also to vary considerably between individuals. Here, single-cut pattern measurement with power integration is discussed for estimating the absorbed power. This means that the power in the single pattern cut should be proportional to the total radiated power. In practice, this is not always the case, but indicative and useful results can still be obtained. Experimental results using a phantom head are given and simple retrofit parasitic shields are shown to decrease the absorbed power.