2. ANTENNA DESIGN
Figure 1(a) shows a typical geometry of a printed PTMA which consists of a triangular-shaped radiator on the top and a rectangular-shaped ground plane on the backside of the substrate. It is realized on a FR- 4 substrate (εr =4 .7) with a thickness of 1mm. A 50-Ω center-fed microstrip line on the top layer of the substrate, with the width of 1.8mm, is employed to excite the triangular radiator from its apex. The height and flare angle of the triangular radiator are denoted as hmono and α, respectively. The length of the feeding gap is denoted as hgap. The length hgap and the flare angle α exhibit a significant influence on the impedance bandwidth of the printed PTMA [13,36]. Here, the flare angle is set to be 90◦ and the optimum distance hgap is 0.9mm. The dimension of the rectangular-shaped ground plane on the backside of the substrate is 30mm×15mm. All parameters of the printed PTMA are summarized in Table 1. The impedance bandwidth of the above PTMA is not capable to cover the 3–10GHz UWB band (see Figs. 3 and 5). In order to enhance the impedance bandwidth of the conventional PTMA, a novel and simple means of ridging the rectangular-shaped ground plane is presented. As shown in Fig. 1(c) and (d), the ridged ground planes with two symmetrically hillside-shaped corrugations, the triangle- ridged and trapezoid-ridged shapes, offer a smooth transition from the feeding line to the radiating element for achieving a wide impedance bandwidth. For the PTMA with the triangle-ridged ground planes,
2. ANTENNA DESIGNFigure 1(a) shows a typical geometry of a printed PTMA which consists of a triangular-shaped radiator on the top and a rectangular-shaped ground plane on the backside of the substrate. It is realized on a FR- 4 substrate (εr =4 .7) with a thickness of 1mm. A 50-Ω center-fed microstrip line on the top layer of the substrate, with the width of 1.8mm, is employed to excite the triangular radiator from its apex. The height and flare angle of the triangular radiator are denoted as hmono and α, respectively. The length of the feeding gap is denoted as hgap. The length hgap and the flare angle α exhibit a significant influence on the impedance bandwidth of the printed PTMA [13,36]. Here, the flare angle is set to be 90◦ and the optimum distance hgap is 0.9mm. The dimension of the rectangular-shaped ground plane on the backside of the substrate is 30mm×15mm. All parameters of the printed PTMA are summarized in Table 1. The impedance bandwidth of the above PTMA is not capable to cover the 3–10GHz UWB band (see Figs. 3 and 5). In order to enhance the impedance bandwidth of the conventional PTMA, a novel and simple means of ridging the rectangular-shaped ground plane is presented. As shown in Fig. 1(c) and (d), the ridged ground planes with two symmetrically hillside-shaped corrugations, the triangle- ridged and trapezoid-ridged shapes, offer a smooth transition from the feeding line to the radiating element for achieving a wide impedance bandwidth. For the PTMA with the triangle-ridged ground planes,
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