Prediction of antennas radiation efficiency in resonance regions via contactless Wheeler cap measurements

A contactless Wheeler cap setup is proposed to measure the radiation efficiency of arbitrary moderate size antennas. A magnetic conductor flange surrounds the conventional Wheeler cap opening to be parallel to a conducting/nonconducting ground plane. Such arrangement suppress the leakage from the cavity without a need for electrical contact. The magnetic conductor is realized by an Electromagnetic Band Gap (EBG) surface. The fabricated design exploits cascaded and stacked mushroom-shaped unit cells to cover a wide operating frequency band (1.5-4 GHz) in a compact size. Also, the recently introduced semi-analytical quality factor method is employed to accurately predict antenna radiation efficiency with complete immunity of cavity modes´ effects. Finally, the design is verified with full-wave simulations and measurements for different antenna types.