Triple-notch UWB monopole antenna with fractal Koch and T-shaped stub

Abstract

In this study, a triple-notch ultra-wideband (UWB) monopole antenna with fractal Koch and T-shaped stub is presented. The prototype antenna is based on a circular monopole antenna with a back-plane feed line modified for 2–11GHz in an omnidirectional pattern. By implementing a combination of fractal Koch and T-shaped stub on the antenna, a triple-notch band occurred at 2, 3.5, and 5.8GHz for rejecting personal communication services (PCS), worldwide interoperability for microwave access (WiMAX), and wireless local area network (WLAN). In addition to the UWB application frequency range of 3.1–10.6GHz, the final antenna covers a frequency range of 1.78–1.91GHz for GSM 1800, 2.28–3.120GHz for Wi-Fi, and 2.4GHz for Bluetooth applications with a voltage standing wave ratio (VSWR)<2. Simulated results of HFSS and CST are compared with experimental results. The dimensions of the antenna are 50mm×50mm×1.6mm. The current distribution and efficiency at notch frequency are noted for the whole frequency band, and the maximum antenna gain is between −3.5 and 6.5dBi. In this study, methods using Koch structure and T-shaped stub to achieve triple-notch antenna are implemented in three steps. In addition, the effects of T-shaped stub and fractal Koch on the magnitude of the antenna (S11) are studied.