Parallel Metal Plated U-shape Ultra-wide Band Antenna with WLAN Band-notched Characteristics

In this article, a parallel metal plated ultra-wideband (UWB) antenna with band stop characteristics is proposed. The proposed antenna is a simple U-shaped monopole structure where a rectangular strip is placed on both sides at the top of semi annular ring monopole structure. The band-rejection characteristic is achieved by introducing a lambda/4 open stub in the microstrip feeding line to prevent interference due to WLAN (wireless local area network) systems operating within ultra-wideband. To achieve the desired UWB response with WLAN band notched characteristics, the dimensions of rectangular strip, length and width of stub, and the gap between the ground plane and the radiating structure are optimized. Frequency rejection characteristics depend on the dimension of stub and can be fine controlled using other parameters. The proposed antenna is simulated, fabricated and tested. The antenna structure is designed using 0.5 mm thick copper metal plate for ground plane and radiating structure and 0.6 mm thick foam dielectric is placed between them. The relative permittivity (epsilon(r)) 1.06 and loss tangent (tan delta) of foam are 1.06 and 0.0 respectively. The antenna structure is fed through a 50 Omega microstrip line using a SMA connector. The results show that the S-11 <= -10 dB from 3.09-11.1 GHz except 4.4-6.4 GHz frequency band. The proposed antenna provides more than 95% antenna efficiency and gain varies from 3-6 dB over the 3.09-11.1 GHz range except in 4.4-6.4 GHz notched band. The structure exhibits nearly omnidirectional radiation patterns, stable gain, and small group delay variation over the desired bands.