In this paper, two miniaturized (20 × 20 mm 2 ) coplanar waveguide fed slot antennas are proposed. Both the antennas are characterized by ultra wide impedance bandwidth while one of them has an additional narrow band near 2.5 GHz. The radiating element of the proposed antennas is a modified rectangular geometry which is excited by a 50 ohm line. The slot in the ground plane is stair case shape for UWB antenna and octagonal shape for the dual-band antenna. By modifying the slot and adding a λ/4

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... ength metallic stub, an extra resonance is created for the dual-band antenna. The measured impedance bandwidth of the UWB antenna is 7.8 GHz (3.4-11.2 GHz). The impedance bandwidths of the dual-band antenna are 150 MHz (2.45-2.6 GHz) and 8.4 GHz (3.2-11.6 GHz). The radiation patterns of the proposed antenna are found to be bi-directional in E-plane and omni-directional in H-plane. All the measured and simulated results are in good agreement.