In this article, an ultrawideband (UWB) antenna with triple
band-rejection characteristics is proposed. The antenna is compact
with size of 22.5 3 24 mm2. Matching between a sector-disk shaped
radiating patch and the 50-X microstrip line is manipulated through a
proximity-feed technique. An elliptically-shaped aperture is etched in the
ground plane to enhance the antenna bandwidth. Double shunt stubs are
used to get more enhancement of the impedance bandwidth of the antenna. The band notches at WiMAX of 3.3–3.9 GHz, lower WLAN of
5.15–5.35 GHz, and upper WLAN of 5.725–5.825 GHz are realized by
embedding three elements; a reversed F-shaped slot etched off in the
patch, a reversed U-shaped slot etched off in the feed line, and adding a
parasitic flipped C-shaped strip around the patch, respectively. The
antenna is fabricated and the experimental data show that the designed
antenna has an impedance bandwidth of 3.2–11.6 GHz for VSWR less
than 2, except at three frequency stop-bands of 3.20–4.19, 5.02–5.32, and
5.51–6.10 GHz. Curve fitting formulations to describe the influences of
the embedded structures on the corresponding notched frequencies are
obtained by using a second-order polynomial. Moreover, physical lumped
elements of an electrical equivalent circuit model of the proposed antenna
are obtained using a rational function approximation based on the vector
fitting technique. The antenna provides almost omnidirectional patterns,
relatively flat gain, and high radiation efficiency over the entire UWB
frequency excluding the rejected bands. VC 2014 Wiley Periodicals, Inc.
Microwave Opt Technol Lett 56:646–654, 2014; View this article online
at wileyonlinelibrary.com. DOI: 10.1002/mop.28149