Contents I. Introduction
Printed slot antennas are attractive because of their wide impedance bandwidths, low cost, planar structures and easy integration with active devices or MMICs. Thus, great interest in various printed slot antennas can be seen in the literature. In recent years, some microstrip-line-fed printed slot antennas [1]–[5] have been reported because of their favorable impedance characteristics. In the reported literature [5], a printed slot antenna with a fork-like tuning stub has been shown to have a good bandwidth enhancement. However, the structure of microstrip feed line used in [5] makes the configuration of the slot antenna more complicated. Another printed microstrip-line-fed slot antenna with a simple rotated slot for a wider bandwidth has also been studied in [6]. As a result, a wide operating bandwidth of about 2200 MHz (49.4%) with respect to the center frequency at 4453 MHz has been obtained. However, it is not enough for the operating bandwidth to cover more wireless communication services. In this paper, a new design of microstrip-line-fed printed slot antenna with a pair of parasitic strips is proposed and investigated. In this design, a smaller ground plane is considered. By choosing proper dimensions of the ground plane and parasitic strips, it is seen that more resonant modes operating near the center frequency of the conventional slot antenna can be obtained. With these resonant modes, the proposed antenna can have similar radiation patterns and the same polarization. From the experimental results, the obtained impedance bandwidth (10 dB return loss) of the proposed antenna can operate from 1.80 to 6.09 GHz with a center frequency at around 4 GHz.
