A Compact Fractal-Shaped Antenna for Ultrawideband and Bluetooth Wireless Systems With WLAN Rejection Functionality

A compact planar quasi-self-complementary antenna is presented for ultrawideband applications. The antenna also radiates at Bluetooth frequency band centered at 2.4 GHz and exhibits band rejection at 5.5 GHz. A Koch fractal boundary is embedded over the hexagonal-shaped radiator to improve the input impedance matching of the antenna at higher frequencies. An arc-shaped protruded ground plane is incorporated to match the input impedance of the antenna at lower frequencies. A modified meandered-shaped stub is introduced to resonate at Bluetooth frequency band. The property of band rejection is achieved by etching a quadratic fractal slot on the radiator. Overall size of the antenna is 18.5 x 39 mm(2). The antenna shows almost a constant group delay with a deviation of 1 ns throughout the operational bandwidth and also has a stable radiation pattern. An equivalent circuit is also developed for the proposed antenna. The results obtained from circuit model, electromagnetic simulation, and measurement are in good agreement.