Antenna and Wave Propagation

Prof. Pushpendra Singh

BIT Durg
 Antennas and Wave Propagation - Syllabus
Course Objectives:
•To study guided wave propagation in metallic wave guides
•To study radio wave propagation
•To study the concept of radiation and analyze radiation characteristics of a current
element and dipole
•To study antenna fundamentals and antenna arrays: uniform and tapered and their
design
•To study some practical antennas like rhombic; Loop, yagi and log periodic antenna.
Course outcomes:
• Student is able to understand the guided and unguided
wave propagation.
• Student gets knowledge of Basic antennas, their radiation and
characteristics.
• Student gets knowledge of antenna arrays and their design.
• Student is able to understand some practical antennas.
 Frequency Ranges and Applications - RF (Radio Waves)
Sl. No. Band Name Frequency Range Typical Applications

1 VLF 3kHz-30KHz Telegraphy.

2 LF 30kHz-300kHz Marine and navigational aids, long

distance point to point service.
3 MF 300kHz-3MHz AM broadcast, navigation, Horbour
telephone etc.
4 HF 3MHz-30MHz Aircraft radio, short wave
broadcasting to distant places.
5 VHF 30MHz-300MHz FM, TV, radar, Telephony and so on.

6 UHF 300MHz-3GHz Radar, TV, short distance commn.

7 MICROWAVE 3GHz-30GHz Radar, satellite commn and so on.

8 EHF 30GHz-300GHz Experimental purposes, Amateur,

government.
N.K.Dewangan, Asso. Prof.(Sr.Scale), BIT,
4
Durg.
 Unit - III, IV, V
Antennas
Definition:
• It is an electrical device which converts electric power into radio waves, and
vice versa. It is usually used with a radio transmitter or radio receiver.

 In transmission, a radio transmitter supplies an electric current oscillating

at radio frequency (i.e. a high frequency alternating current (AC)) to the
antenna's terminals, and the antenna radiates the energy from the current
as electromagnetic waves (radio waves).
 In reception, an antenna intercepts some of the power of an
electromagnetic wave in order to produce a tiny voltage at its
terminals, that is applied to a receiver to be amplified.
 Figure 1:
 Components
• Antennas are essential components of all equipment that uses radio.
• They are used in systems such as:
– radio broadcasting,
– broadcast television,
– two-way radio,
– communications receivers,
– radar,
– cell phones,
– satellite communications,
– wireless microphones,
– Bluetooth-enabled devices,
– wireless computer networks,
– baby monitors, and
– RFID tags on merchandise.
 Diagram of the electric fields (blue) and magnetic
fields (red) radiated by a dipole antenna (black
rods) during transmission.

Half-wave dipole antenna

(Transmission)

Half-wave dipole antenna

(Receiver side)

Half-wave dipole antenna

Whip antenna on car, common
example of an omni-directional
antenna Mast radiator antenna of medium
wave AM radio station, Germany
Yagi-Uda television antenna for analog
channels 2-4, 47-68 MHz

Log-periodic antenna covering

140-470 MHz
Loop direction finding
antenna covers 1.75 -
30 MHz, 6 ft diameter

Microwave horn antenna

bandwidth 0.8–18 GHz
 Unit - I
Wave Guides

Definition

A Hollow metallic tube of

uniform cross section for
transmitting electromagnetic
waves by successive
reflections from the inner
walls of the tube is called
waveguide.
 Waveguide components

Rectangular waveguide Waveguide to coax adapter

Waveguide bends E-tee

15
 Basic features
 Waveguides may be used to carry energy between pieces
of equipment or over longer distances to carry transmitter
power to an antenna or microwave signals from an
antenna to a receiver

 Waveguides are made from copper, aluminum or brass.

These metals are extruded into long rectangular or circular
pipes.

 An electromagnetic energy to be carried by a waveguide is

injected into one end of the waveguide.

 The electric and magnetic fields associated with the signal

bounce off the inside walls back and forth as it progresses
down the waveguide.
EM field configuration within the waveguide

 In order to determine the EM field configuration

within the waveguide, Maxwell’s equations
should be solved subject to appropriate
boundary conditions at the walls of the guide.

 Such solutions give rise to a number of field

configurations. Each configuration is known as
a mode. The following are the different modes
possible in a waveguide system
 Possible Types of modes

1. Transverse Electro Magnetic (TEM) wave:

• Here both electric and magnetic fields are
directed components. (i.e.)
E z = 0 and Hz = 0

2.Transverse Electric (TE) wave:

• Here only the electric field is purely transverse
to the direction of propagation and the magnetic
field is not purely transverse. (i.e.)
E z = 0, Hz ≠ 0
 Possible Types of modes

3. Transverse Magnetic (TM) wave:

• Here only magnetic field is transverse to the
direction of propagation and the electric field is
not purely transverse. (i.e.) E z ≠ 0, Hz = 0.

4. Hybrid (HE) wave:

• Here neither electric nor magnetic fields are
purely transverse to the direction of
propagation. (i.e.) E z ≠ 0, Hz ≠ 0.
 Unit – II
WAVE PROPAGATION
 Modes of Propagation
When EMW is produced by an antenna it moves from the
transmitter to the receiver in the following ways:

1. A part of the wave travels along or near the surface of the

earth. This wave called the ground wave or surface wave
(upto 2 MHz).

2. Some waves travel directly from the transmitting to the

receiving antenna. That is, these waves do not follow the
earth and also do not move towards the sky. These waves
are called space waves (> 30 MHz).

3. Some waves travel upwards into space towards the sky and
get reflected back to the receiver. These waves are called sky
waves (2-30MHz).
Rectangular Waveguides

25
Propagation of Wave in Rectangular Waveguide

26
Propagation of Wave in Rectangular Waveguide

27
Propagation of Wave in Rectangular Waveguide

28
Propagation of Wave in Rectangular Waveguide

29
Propagation of TM Wave in Rectangular Waveguide

30
Propagation of TM Wave in Rectangular Waveguide

31
Propagation of TM Wave in Rectangular Waveguide

32
Propagation of TM Wave in Rectangular Waveguide

33
Propagation of TM Wave in Rectangular Waveguide

34
Propagation of TM Wave in Rectangular Waveguide

35
Propagation of TM Wave in Rectangular Waveguide

36
Propagation of TM Wave in Rectangular Waveguide

37
TM Modes in Rectangular Waveguide

38
Cut-off Frequency of a Waveguide

39
Cut-off Frequency of a Waveguide

40
Guide Wavelength, Group and Phase Velocity
Guide Wavelength:

41
Guide Wavelength, Group and Phase Velocity

42
Guide Wavelength, Group and Phase Velocity
Phase Velocity:

43
Guide Wavelength, Group and Phase Velocity
Group Velocity:

44
Relationship between Guide Wavelength, Group
and Phase Velocity

45
TM Modes in Rectangular Waveguide

46