Improved radiation efficiency measurement of mobile systems and application to a novel multiband antenna

In this paper an improved method for measuring the radiation efficiency of small devices is introduced. The method is based on Wheeler's principle of measuring the antenna impedance within two controlled environments: free space and a closed metallic box. An extended equivalent circuit is introduced, that gives an exact description of the behavior of the small device within the metallic box. This model is the basis for the determination of the radiation efficiency, independent of the size of the box and the location of the device within the box. In the next part of the paper, a concept for an integrated up-to-date multiband antenna for a GSM mobile phone is presented. The characterization of the radiation efficiency by the above mentioned method proves the new way to characterize the efficiency.