Deep band-notched ultra-wideband planar monopole antenna using meander lines

Abstract

The article presents the design of a planar ultra-wideband (UWB) monopole antenna with a deep band-notched characteristic. The antenna has an elliptical radiator fed by a microstrip line and a small ground-plane size of 30×15 mm². Two pairs of meander lines (MLs) are employed to implement the deep band-notched characteristic. One pair of the MLs is placed closely on both sides of the microstrip-feed line with one of their ends shorted to ground. The other pair is placed at the upper edges of the ground plane on the other side of the substrate. The frequency range of the notched band can be controlled by the dimensions of the MLs. In our studies, the notched band is designed in the frequency band from 5.1 to 5.85 GHz to suppress the signals in the WLAN system. The antenna is studied and optimized using computer simulation. For verification of simulation results, the antenna is fabricated and measured. Results show that, by using the two pairs of MLs, the gain of the antenna at the notch frequency can be suppressed by 14 dB, with the efficiency reduced to less than 5%. Due to the small ground-plane size used in the antenna, the feeding cable used for measurements in the measurement equipment has significant effects on the measured results. This leads to large discrepancies between the simulated and measured results at low frequencies. To study this, the model of the feeding cable is also included in simulation and the results show that the discrepancies are substantially reduced. © 2013 Wiley Periodicals, Inc.