## Central composite design experiments CCD with responses coded

3.2.1. Parametric study by CST

The parametric study of OPYIG was conducted to obtain the optimum positioning of the OPYIG pellets within the antenna design, before possible fabrication and measurement. The DRA simulation was carried out using commercially available software, CST-Suite Studio 2008. This study is important to determine the efficient coupling of the OPYIG with the microstrip line. Through this IPA-3 coupling, OPYIG is directly placed on top of microstrip line (feeder) and centered so that OPYIG experienced HEM11 mode (as shown in Fig. 2). Afterwards, the distance of the optimum OPYIG position was compared with actual measurement. The resonance frequencies observed in genome mode could be predicted by the following equations [26].equation(4)fHEM11=18.982×1082πrεr+20.27+0.36r2t+0.02r2t2where f is the resonant frequency, εr is the dielectric constant, meanwhile both r and t are the dimensions that represent radii and thickness of OPYIG, respectively.

Fig. 2. The direction of the DRA from feeder edge (v-axis) in determination of the strong electric and magnetic field coupling.Figure optionsDownload full-size imageDownload as PowerPoint slide