A Small Scale Circular Polarized Reader Antenna with Wide Beamwidth for RFID Applications

Abstract

A small-scale circular polarized (CP) wide beam reader antenna is being presented in this article. Single feed, rectangular-slotted patch antenna is designed with a size of $0.24\lambda_{0}\times 0.24\lambda_{0}$ at UHF (840–960) MHz for RFID applications. Free-space wavelength corresponding to the resonant frequency is $\lambda_{0}$. Wide rectangular slotted patch on the front side and inverted L shaped feed line on the back side have been implanted to help this antenna for size reduction. The circular polarize radiation is been carry through in two steps, one is by switching the feedline and another is by placing an antithetical L-parasite strip into the rectangular slot. This two L-parasite strips on the both side have been connected through metal via. Therefore, the combined effect of horizontal and vertical polarization assures to sustain wide beamwidth. The antenna results carry out of 70MHz, 10 dB impedance bandwidth and 29MHz, 3dB axial ratio bandwidth (ARBW) within the operating band. Half-power beamwidth in X-Z radiation plane is achieved to reach 110°. With maintaining the 3.32dB overall gain, this antenna established itself as a competent CP antenna for RFID application.