Untitled

Abstract

Microstrip antennas suffer from low gain bandwidth product due to surface wave effects and aperture diffractions that limit their use for longrange communications. On top of that, the difficulty of achieving a pure circularly polarized radiation with high gain due to the feeding structure effects. This paper is subjected to design a gain enhanced circularly polarized patch antenna using Uniplanar Compact-Photonic Band Gap (UC-PBG) structu.res for UHF RFID applications. The patch is structured as truncated corners with cross slots at the centre mounted on an FR-4 epoxy substrate of 1.6mm thickness with an overall area of 188×188mm 2. The UC-PBG is constructed of two layers; each is made of 7×7 unit cells, separated by 20mm mounted from the top of the patch at 30mm height. The unit cell characterizations are evaluated in terms of their S-parameters and dispersion diagram CST-MWS environment. The antenna shows a boresight gain of about 8.2 dBi at 915MHz with a front to back ratio (F/B) of 13dB. The benchmark enhancement in boresight gain after adding the UC-PBG layers is found to be 3.4 dBi with a radiation efficiency of 87%. Finally, an excellent agreement is achieved between the obtained measurements and numerical results.