Microstrip ring antenna on grooved substrate for the enhancement of radiation efficiency

The dielectric losses and excitation of surface waves inside substrates decrease the gain and efficiency of microstrip antennas. However, low loss dielectric substrates may increase the antenna efficiency, but they do not decrease the generation of surface waves. In this paper, we propose to remove some portions of the substrate not located under the antenna patch layout, for the objective of eliminating the conditions of propagation of surface waves, which eventually leads to the increase of antenna radiation efficiency. Specially, we apply the proposed method to a dual-arm monopole antenna with favorable results.