High Efficient and Ultra Wide Band Monopole Antenna for Microwave Imaging and Communication Applications

The paper presents a highly efficient, low cost, ultra-wideband, microstrip monopole antenna for microwave imaging and wireless communications applications. A new structure (z-shape, ultra-wideband (UWB) monopole) is designed, which consists of stepped meander lines to achieve super-wide bandwidth and high efficiency. Three steps are used to design the proposed structure for the purpose to achieve high efficiency and wide bandwidth. The antenna bandwidth is enhanced by varying the length of meander line slots, optimization of the feeding line and with the miniaturization of the ground width. The simulated and measured frequency bands are 2.7-22.5 GHz and 2.8-22.7 GHz (156% fractional bandwidth), respectively. The dimensions of the antenna are 38 mm x 35 mm x 1.57 mm, and its corresponding electrical size is 2.41 lambda g x 2.22 lambda g x 0.09 lambda g, where guided wavelength lambda g is at the center frequency (12.75 GHz). This antenna achieved a high bandwidth ratio (8.33:1). The realized gain is varying from 1.6-6.4 dBi, while that of efficiency is 70% to 93% for the whole band. Radiation patterns are measured at four operating frequencies. It has an acceptable group delay, fidelity factor, and phase variation results that satisfy the limit of ultra-wideband in the form of the time domain.