A coplanar waveguide-fed planar hexagonal monopole ultra-wideband antenna with dual-band rejection characteristics is proposed in this paper. The desired notch frequencies at 3.5 and 5.5 GHz are realized by incorporating mushroom structures. The input impedance and surface current distributions are used for analysis and explanation of the effects of mushroom cells. The prototype and proposed antennas are fabricated and tested. From the measured results, the proposed antenna provides an operating band of 2.81–14.32 GHz for 2 ≤ voltage standing wave ratio (VSWR), while the dual-band stop function is in the frequency bands of 3.3–3.7 GHz and 5.10–5.88 GHz. Moreover, the antenna model also exhibits constant group delay and linear phase in the pass band. The proposed antenna has appreciable gain and efficiency over the whole operating band except the notch bands.
