Radiation efficiency of small loop antennas for pager

It is well known that the radiation efficiency of small loop antennas used for pagers is very low since the size of the antenna is much smaller than the wavelength. The low efficiency is considered to be caused by the conducting loss of the antenna conductor. However, any accurate analysis has not been performed to show the mechanism of the low efficiency. In this report, numerical results of the moment method analysis of a small loop antenna with a ground plane and a matching circuit involving condensers are presented and the dielectric loss of the condensers as well as the conducting loss of the antenna and the feeding circuit are shown. Experimental results are also presented to demonstrate the improvement of the efficiency.