Antenna Theory Tutorial

Antenna Theory is a fundamental course in the field of electronics and communication engineering (ECE). It deals with the study of design, working, and applications of antennas in communication systems. As we know, antenna is one of the important components of a communication system that performs transmission and reception of electronic signals.

Antenna theory is introduced as a core subject in the electronics and communication engineering curriculum. This provides students a deep understanding of how different types of antennas function, where different antennas are used, etc. Therefore, for electronics engineers, especially working in the field of communication technologies, antenna theory is an essential course.

Antenna theory also plays an important role in development of modern communication systems like wireless communication, satellite communication, optical fiber communication, radar technology, etc. This course introduces important principles for optimized signals transmission and efficient communication of data and information.

Introduction to Antenna Theory

The primary objective of this Tutorial on Antenna Theory is to provide an overview of the wide range of concepts related to antennas like design, principles and their applications. Understanding these concepts is very important for performing tasks related to antenna design, operation, and maintenance in various communication systems.

For easier understanding of the concepts, this tutorial on Antenna Theory is divided into five modules −

1. The first module explains the various fundamental concepts and basic terms related to antenna theory. Some of the major topics covered here include basic parameters of antenna theory, meaning of near and far fields, radio pattern, concept of beam and polarization, calculation of beam width, property of reciprocity, and Poynting vector.

2. The second module describes different types of antennas and their properties. The major types of antennas explained in this section are half-wave and full-wave dipole antennas, half-wave folded dipole antennas, short dipole antenna, long wire antenna, V and Inverted V antennas, Rhombic antenna, loop antenna, helical antenna, aperture antenna, horn antenna, slot antenna, micro strip antenna, lens antenna, and parabolic reflector. Each of these antennas are explained in detail along with its advantages, disadvantages, and applications.

3. The third module explains different types of antenna arrays. It discusses topics like antenna arrays, collinear array, broad-side array, end-fire array, parasitic array, Yagi-Uda antenna theory, log-periodic antenna theory, and Turnstile antenna theory.

4. The fourth module is on wave propagation and covers topics like terms in wave propagation, spectrum and transmission, types of propagations, and ionosphere and its layers.

5. The fifth module of this tutorial provides a quick guide, suggested useful resources, and a community discussion platform on antenna theory.

Prerequisites to Understand Antenna Theory

This tutorial on Antenna Theory is written at a somewhat basic level and is intended for absolute beginners having a basic understanding of electronics and communication systems. Thus, it may be used as an introductory resource on antenna theory by undergraduate students as well as a reference by practicing electronics and communication engineers.

FAQs on Antenna Theory

There are some very Frequently Asked Questions (FAQs) about Antenna Theory and they are briefly answered in this section.

1. What is the antenna theory?

Antenna Theory is a core subject in the electronics and communication engineering discipline. It deals with the study of design, operation, and applications of different types of antennas used in communication systems.

An antenna is a component of a communication system that can convert electric signals into electromagnetic waves and vice-versa. Thus, it is used as a device for transmitting and receiving signals in the form of electromagnetic waves of distances.

Studying antenna theory involves understating various concepts of communication such as radiation patterns, near and far fields, polarization, types of antennas, antenna arrays, wave propagation, etc.

2. What is the basic principle of antenna?

The basic principle of antenna is to convert electric signals into electromagnetic waves and vice-versa. Apart from signal to wave conversion, an antenna can also perform transmission and reception of electromagnetic waves. These functions form the foundation of all radio communication systems.

3. What is the transmitting antenna theory?

Transmitting antenna theory is nothing but the concept that explains how an antenna converts electric signals into electromagnetic waves and transmit them into space. This theory involves generation of electromagnetic waves from time-varying electric signals and their radiation away from the antenna for communication of information.

4. What are the three types of antennas?

Antennas can be mainly classified on the basis of their directional characteristics into the following three types −

• Directional Antennas
• Semi-directional Antennas
• Omni-directional Antennas

1. Directional Antennas are those that radiate electromagnetic waves in a specific direction and provide a focused and narrow beam of radiation. Due to ability to produce a strong radiation signal in a specific direction, these antennas are used for long distance communication.

2. Semi-Directional Antennas are those types of antennas that can radiate electromagnetic waves in a specific direction but with a wider bandwidth as compared to directional antennas. Due to wider directional radiation pattern, these antennas are widely used in wireless networks, cellular communication, point-to-point communication, etc.

3. Omni-Directional Antennas are those antennas that equally radiate electromagnetic waves in all horizontal directions and provide a coverage of 360. The radiation pattern of these antennas is of doughnut shape. These antennas are commonly used where uniform coverage is required over large geographical area such as FM radio, Wi-Fi, mobile phone base stations, etc.

5. How do antennas work?

The working of a typical antenna is explained in the following simple steps −

Step 1 − A communication transmitter supplies an AC signal to the antenna and it creates an oscillating electric field in the antenna.

Step 2 − The oscillating electric field produces a time-varying magnetic field around the antenna. The combined effect of time-varying electric and magnetic fields form electromagnetic waves emitting out from the antenna.

Step 3 − The emitted electromagnetic waves have a specific radiation pattern depending on the design of the antenna.

Step 4 − These electromagnetic waves are radiated away from the antenna and received by another antenna in the communication system. Where, these waves induce an AC signal in the receiver antenna and the EM waves are converted back into electric signals.

Step 5 − These electric signals are collected and processed by the receiver to retrieve the original information.

These five steps show how a typical antenna works in a communication system.

6. What are antenna properties?

Antenna properties are parameters that determine the performance of the antenna. The following are some key properties of antennas −

• Radiation Pattern − This antenna property describes how the antenna radiates electromagnetic waves in space. It could be directional, semi-directional, or omni-directional.
• Gain − This antenna property describes the ability of the antenna to increase radiated power.
• Directivity − This property of an antenna gives the measure of power radiated in a specific direction over the power radiated in all directions.
• Bandwidth − This property defines the frequency range over which the antenna can operation efficiently.
• Polarization − This property of antennas specifies the orientation of electric field of the radiated electromagnetic waves. It could be horizontal, vertical, circular, and elliptical.
• Efficiency − This property of antenna gives the measure of power radiated over the total amount of power input to the antenna. It also provides losses in the antenna.

7. What are the applications of antenna?

Antenna is an important component of a communication system or communication device. Some common applications of antennas are listed here −

• Mobiles and Wi-Fi to provide wireless communication
• Radio and TV broadcasting
• Satellite communication
• GPS (Global Positioning System) and navigation
• Radar systems
• Remote sensing and control, etc.

8. What is the theory of slot antenna?

The theory of slot antenna is based on the concept of complementary antennas. According to this concept, a slot antenna is constructed by using a conductive metallic surface usually a flat plate. This metallic surface is cut out with one or more slots or holes into it. On the application of radio frequency current signals, the slots act as a radiator and produces electromagnetic waves. The pattern, frequency, and polarization of these electromagnetic waves is determined by the dimension and orientation of slots.

9. What are the two main functions of antenna?

In communication systems, an antenna performs the following two main functions −

• Transmission of Electromagnetic Waves − Antenna converts electric signals into electromagnetic waves and transmit them to the destination.
• Reception of Electromagnetic Waves − Antenna receives electromagnetic waves and convert them into electric signals to retrieve original information.

10. Who invented the antenna?

A German physicist, Heinrich Hertz was invented the first antenna in the year of 1888. This antenna was a parabolic antenna, which is also known as a satellite dish. In this antenna, Hertz used spark-excited dipole antenna at the foci of the cylindrical parabolic reflector to perform transmission and reception of electromagnetic waves.

11. What is wave propagation?

The movement of electromagnetic waves in the space or a medium is known as wave propagation. In communication engineering, wave propagation is nothing but the radiation of electromagnetic waves containing information between transmitter antenna and receiver antenna.

12. What are the modes of wave propagation in antenna?

In the case of an antenna, modes of wave propagation are defined as the ways in which electromagnetic waves move from transmitter antenna through space to the receiver antenna. The following are some common modes of wave propagation in antennas −

• Ground Wave Propagation − In this wave propagation mode, the electromagnetic waves move along the surface of the Earth. This mode of wave propagation is commonly used in short-range communication like AM radios.
• Sky Wave Propagation − In this wave propagation mode, electromagnetic waves travel to the receiver by reflecting back to the Earth by the ionosphere. This mode of wave propagation is commonly used in long distance communication like TV broadcasting.
• Line of Sight Propagation − In this mode of wave propagation, electromagnetic waves travel in a direct visual path without any reflection or diffraction. This mode is commonly used in very-high frequency and ultra-high frequency communication.
• Free Space Propagation − In this wave propagation mode, the electromagnetic waves travel in a straight line from transmitter to the receiver in an open space environment. This mode is widely used in satellite communication.

13. What are the properties of antenna array?

The following are some important properties of antenna arrays −

• Gain − This property describes how effectively the antenna array can convert input electric signals into electromagnetic waves in a particular direction.
• Directivity − This property describes the ability of an antenna array to focus electromagnetic radiation in a specific direction.
• Interference Cancellation − This property explains how the antenna array can cancel the interference from particular directions.
• Beam Steering − This property of an antenna array provides ability to electronically steer the electromagnetic radiation without physically moving the antenna array. This property involves the phase control of the signals.

14. What is the advantage and disadvantage of array antenna?

The key advantages and disadvantages of array antennas are highlighted below −

Advantages of Antenna Array

• Antenna array provides higher gain and increased directivity.
• Antenna array offers improved signal-to-noise ratio (SNR).
• Antenna array reduces unwanted radiation in other directions.
• Antenna arrays offer high flexibility in terms of scalability and customization.

Disadvantages of Antenna Array

• Antenna arrays are relatively complex to design and maintain.
• Due to multiple antennas used, array antennas are costlier.
• Antenna arrays have larger size and higher weight.
• Array antennas consume more power.

15. What is the principle of wave propagation?

The principle of wave propagation involves the production, transmission, and reception of electromagnetic waves containing information.

The principle of wave propagation is described by various physical laws like Maxwells equations. These equations explain the interaction of electric and magnetic fields, and describe the behavior of electromagnetic waves.