A new compact broadband circular fractal antenna is presented to simultaneously cover the operations in S-, C-, X-, and Ku-bands. Fractal geometry of the radiator including an iterative circular patch with a square slot, a modified feed-line with step technique, and slot-loaded semi-circular ground plane is used to achieve a broad impedance bandwidth more than 151% from 3 to 21.5 GHz (|S11|< -10 dB). The simulation results are verified by experimental measurements. Measured data are in good agreement with the simulated results. The frequency- and time-domain characteristics of the antenna including impedance matching, far-field patterns, gain, group delay, and fidelity factor are presented and discussed. The proposed broadband antenna features small size of 38×36×1.4 mm3 and nearly omnidirectional radiation patterns that make it excellent candidate for integration in broadband wireless communication systems.
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