Radiation Blockage Reduction in Antennas Using Radio-Frequency Cloaks [Antenna Applications Corner]

This article presents an experimental demonstration of antenna blockage reduction based on the concept of radio-frequency (RF) cloaking. The proposed cloaking configuration is validated by studying the antenna characteristics in the presence of obstacles that are covered with and without the cloaking surface. The known concept of thin cloaks used for reducing the scattering width is extended in this article to mitigate the blockage in antennas. An attempt is made to improve the degraded radiation characteristics of the antenna due to the presence of metal obstacles loaded in front of the aperture. This is accomplished by covering the obstacles with a cloaking surface made up of a periodic arrangement of interconnected patches and microstrip lines. The optimizations are carried out for various scenarios by varying the thickness of the substrate and the length of the interconnecting microstrip line to achieve an optimum cloaking performance. It is demonstrated through measurements that the RF cloaking could be achieved between the frequencies 3 and 3.3 GHz. At 3.2 GHz, the gain of the horn antenna in free space is measured to be 17.2 dBi, and the gain of the horn antenna with uncloaked obstacles at the aperture is 3.73 dBi. The same configuration with cloaked obstacles exhibits a gain of 12.13 dBi.