GATE Electronics and Communications (EC) 2020 Solved Papers

For an infinitesimally small dipole in free space, the electric field ${\mathit{E}}_{\mathit{\theta }}$ in the far field proportional to $\left({\mathit{e}}^{-\mathit{j}\mathit{k}\mathit{r}}/\mathit{r}\right)\sin \mathit{\theta }$, where $\mathit{k}=2\mathit{\pi }/\mathit{\lambda }.$ A vertical infinitesimally small electric dipole is placed at a distance $\mathit{h}\left(\mathit{h}>0\right)$ above an infinite ideal conducting plane, as shown in the figure. The minimum value of $\mathit{h}$, for which one of the maxima in the far field radiation pattern occurs at $\mathit{\theta }={60}^{\circ }$, is