A simple shape broadband planar antenna adaptable to RFID-tag

This paper presents a simple shape planar antenna with high adaptability to an Radio Frequency IDentification tag. The feed point of this antenna consists of two adjacent electrodes in the plane which can be matched to the intrinsic impedance of a coaxial cable (50-Ω) without using parasitic elements or balun. Specifically, the aperture shape inside the loop antenna is modified without deforming the antenna element outline. Control of the input impedance becomes possible and bandwidth for S11≤-10 dB can reach about 49% of the central frequency. The proposed antenna demonstrates a steady gain (3.5-4.2 dBi) within a wide frequency range. An investigation of antenna-element miniaturization showed the sectional area of the antenna element could be compressed by about 50% while maintaining wide bandwidth.