مرکز منطقه ای اطلاع رساني علوم و فناوري - Three angles significant in radio propagation

Abstract :

The wave tilt $\\theta$ of the electrical field vector, the Brewster angle $\\psi_{B}$ , and the limiting angle $\\psi_{N}$ (by Norton) play significant roles in some radio propagation problems of communication and target detection, especially in the cases where the electromagnetic waves travel close to the conductive surface, when the polarization of the incident rays is vertical and the radio frequency lies in the HF band or any of the lower frequency regions. The possible relations of these angles is examined. It is shown that under specified conditions: $\\liminf {X \\rightarrow 0} \\tan psi_{B}= \\lgroup frac{\\epsilon}{\\epsilon-1} rgroup^{1/2} \\liminf {X \\rightarrow 0} \\tan \\theta$ , for arbitrary $\\epsilon > 1$ $\\liminf {X \\rightarrow 0} \\psi_{B} \\approx \\liminf {X \\rightarrow 0} \\theta$ , for $\\epsilon \\gg 1$ $\\psi_{B}\\approx \\sqrt {2}\\theta$ , for $X \\gg \\epsilon > 1$ where $X$ is a physical parameter that depends on the frequency of propagation $f$ and the conductivity of the surface $\\sigma$ . The quantity $\\epsilon$ is the dielectric constant. No such relationship exists among $\\psi_{N}$ , $\\psi_{B}$ , and $\\theta$ . However, for given fixed surface variables $\\epsilon$ and $\\sigma$ , one can find a particular value of $f$ for which $\\psi_{N}$ is numerically equal to $\\psi_{B}$ .