Compact microstrip omnidirectional ultrawideband antenna with dual broadband nested U‐shaped slots and flat frequency response

In this article, we present a compact ultrawideband antenna with dual broadband‐notched characteristics centered at 3.4 and 5.5 GHz. The proposed antenna consists of a rectangular patch with a modified ground plane structure and 50 Ω microstrip‐fed line. By etching two opposite U‐shaped slots in the radiating patch, the notched bands of 3.375–3.945 GHz for WiMAX and 5.425–6.150 GHz for WLAN and HYPERLAN/2 were achieved. The antenna also offers a flat frequency response so minimizing the formation of spurs and precursors that ensures optimal time domain performance for ultrawideband radio applications. The return loss was measured to better than −10 dB over the entire band from 3.1 to 10.6 GHz. The antenna gain was larger than 2 dBi all over the frequencies with a flatness of 2.5 dB and an omnidirectional radiation pattern in the H‐plane. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2854–2856, 2015