An improved method for measuring the radiation efficiency of mobile devices

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. In addition to Wheeler's network model, 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. Several measurements show that using the new method, the radiation efficiency of mobile devices can be determined very quickly and very accurately.