Because the antenna efficiency is very low, about 1% by the simulation results of IE3D 10. It's that 1% of the input energy is radiated, then where does the other 99% of the input energy go? Could anyone tell me? I followed the file, Compact microstrip antennas for personal mobile communication, which can be found in the IEEE database, the antenna has been reported, but if the efficiency is so poor, then could this kind of antenna be used in actual systems?