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

The radiated power density is symmetrical with respect to $$\phi $$ and exists only in the upper hemisphere: $$0 \le \theta \le {\pi \over 2};\,\,\,\,0 \le \theta \le 2\pi ;$$

$${C_0}$$ is a constant. The power radiated by the antenna (in watts) and the maximum directivity of the antenna, respectively, are