Wideband Circular Polarized Fractal Antenna for RFID/WiMAX/WLAN Applications

Abstract

|A novel wideband circularly polarized (CP) dipole antenna for RFID/WiMAX/WLAN applications is presented. A pair of crossed fan-shaped dipoles printed on both sides of the substrate are used as the primary radiating elements. The antenna achieves circular polarization by using a 90 ◦ phase shifted microstrip line between the dipoles. By changing the edge of fan dipoles into Minkowski fractal curve, miniaturization and wide bandwidth of the antenna can be realized. Besides, incorporating the U-slot into the fractal crossed dipoles can obtain a wider bandwidth. The test results show that the proposed antenna achieves a wide impedance bandwidth of 63.2% (1.9{3.7 GHz) for VSWR < 2 and a 3-dB axial ratio (AR) bandwidth of 42.9% (2.2{3.4 GHz). The maximum gain in the operating frequency band can reach 7 dBi. The proposed antenna has good radiation characteristics in both low and high frequencies, which makes it a candidate for applications of RFID, WLAN, WiMAX, and other communication systems.