Wave Propagation

1. Introduction

Wave propagation is any of the ways in which waves travel. For electromagnetic waves, propagation may occur in a vacuum as well as in a material medium. Most other wave types cannot propagate through vacuum and need a transmission medium to exist.

Free Space propagation

As a wave travels in free space, its power density varies inversely with the square of the distance. When the transmitter horn is fixed and the received powers at different distances are to be different.

Antenna Polarization

Polarization is a property of certain types of waves that describes the orientation of their oscillations. Electromagnetic waves, such as light and gravitational waves exhibit polarization; acoustic waves (sound waves) in a gas or liquid do not have polarization because the direction of vibration and direction of propagation are the same.

In the experiment, the rectangular horn radiating waves can be placed into two orientations.

When the narrower side of the rectangular opening is oriented horizontally with respect to the ground, then the electric field will e in the horizontal plane and the antenna is said to be horizontally polarized

E- Field

Narrow side

Figure 1: Horizontal polarization

When the narrower side of the rectangular opening is oriented vertically with respect to the ground, the electric field will in the vertical plane and the antenna is said to be vertically polarized.

E- Field

Narrow side

Figure 2: Vertical polarization

Transmission through a Dielectric Slab

A dielectric is an electrical insulator that may be polarized by an applied electric field. When a dielectric is placed in front electromagnetic waves, a part of the wave is either reflected or absorbed while the remaining is transmitted. Hence a dielectric slab placed in the wave propagation path to measure the received power. And estimate the transmission coefficients of dielectric slabs of different thickness.

Diffraction

Diffraction is described as the apparent bending of waves around small obstacles and the spreading out of waves past small openings. Once the wave is incident on an object, included secondary sources are formed and they scatter the wave in different directions. In the experiment,