Analysis Of Antenna

CHAPTER 1 INTRODUCTION

1.1 Overview of Antenna:

An antenna is a specialized transducer that converts radio frequency (RF) fields into alternating current (AC) or vice versa. There are two basic types: the receiving antenna, which intercepts RF energy and delivers AC to electronic equipment, and the transmitting antenna, which is fed with AC from electronic equipment and generates an RF field. Also called an aerial, an antenna is a conductor that can transmit, send and receive signals such as microwave, radio or satellite signals [1]. A high

This antenna, also called a doublet is one of the simplest types of antenna, and constitutes tha main RF radiating and receiving element in various sophisticated types of antennas. The dipole is inherently a balanced antenna, because it is bilaterally symmetrical.

1.2.2 Travelling Wave Antenna:

In radio and telecommunication, a travelling-wave antenna is a class of antenna that uses a travelling wave on a guiding structure as the main radiating mechanism. Their distinguishing feature is that the radio frequency current that generates the radio waves travels through the antenna in one direction. This is in contrast to resonant antennas, such as the monopole or dipole, in which the antenna acts as a resonator, with radio currents travelling in both directions, bouncing back and forth between the ends of the antenna. An advantage of travelling wave antennas is that they often have a wider bandwidth [3].

a) Helical

These antennas are commonly used at earth-based stations in satellite communication systems. This type of antenna is designed for use with an unbalanced feed line such as coaxial cable. The center conductor of the cable is connected to the helical element, and shield of the cable is connected to the reflector.

b) Yagi uda antenna:

A Yagi-Uda antenna, commonly known simply as a Yagi antenna, is a directional antenna, consisting of multiple parallel dipole element in a usually made of metal rods. It consists of a single driven element connected to the transmitter or receiver with a transmission line, and additional parasitic elements: a so-called reflector and one or more directors. The reflector element is slightly longer than the driven dipole, whereas the directors are a little shorter. This arrangement shows in figure 1.2.2.

Fig 1.2.2 Yagi Uda Antenna

1.2.3 Reflector Antennas:

An antenna reflector is a device that reflects electromagnetic waves. Antenna reflectors can exist as a standalone device for redirecting radio-frequency (RF) energy, or can be integrated as part of an antenna assembly [3]. Figure 1.2.3 shows reflecting setup of reflecting