A Dual Band Circularly Polarized Antenna with Parasitic Element for Gain Enhancement

A dual band circularly polarized (CP) antenna for WiMAX and WLAN application is proposed. By placing a fork-type parasitic element with a ground plane and a rectangular stub connected to the ground, desirable CP dual band characteristics are achieved. The measured results exhibit %22.2 (3/2-4 GHz) and %21/4 (5-6/2 GHz) impedance bandwidth with axial ratio (AR) of % 21.06 (3/4-4/2 GHz) and %35/7 (4/6-6/6 GHz) for WiMAX and WLAN frequency bands, respectively. Additionally, a novel and simple approach in order to enhance gain of the antenna at the lower frequency is introduced. Indeed, by employing a rectangular shorted parasitic element under the patch, the gain of the proposed antenna is improved nearly 3 dBi. In comparison to recent CP dual band antennas, the proposed antenna has a more desirable gain as well as wide AR bandwidth in both functional bands with a smaller size.