This document discusses different types of antennas used for transmitting and receiving electromagnetic waves. It describes log-periodic antennas, which work over a wide frequency range using a logarithmic size progression of elements. Specific types are described, including bow-tie antennas and log-periodic dipole arrays. Wire antennas like dipoles, monopoles, and loops are also covered. Travelling wave antennas transmit signals along their length, represented by helical and Yagi-Uda antennas. Microwave antennas and reflector antennas are used at higher frequencies for applications like communication and radar. Key antenna properties and a variety of applications are also summarized.

1. ANTENNAS AND WAVE PROPAGATION

2. ANTENNA:
 An antenna is a specialized transducer that
converts radio-frequency (RF) fields into
alternating current (AC) or vice-versa.
 An antenna is a device for sending or
receiving electromagnetic waves

3. Antenna parameters:
• Radiation pattern
• Efficiency
• Bandwidth
• Directivity
• Gain

4. Types of antennas:
Log Periodic Antennas
Wire Antennas
Travelling Wave Antennas
Microwave Antennas
Reflector Antennas

5. Log-Periodic Antennas
It is a multi-element, directional narrow beam
antenna that works on a wide range of
frequencies.
This antenna is made of a series of dipoles
placed along the antenna axis at different space
intervals of time followed by a logarithmic funct
ion of frequency.

6. Types of log period antennas
Bow-Tie Antennas
Log-Periodic Dipole Array

7. Bow-Tie Antennas
• A bow-tie antenna is also known as
Biconical antenna or Butterfly antenna.
• Biconical antenna is an omnidirectional
wide-band antenna.
A bow-tie slot antenna is designed for ra
dar applications.

8. Log-Periodic Dipole Array
• These dipole-array antennas reduce in
size from the back end to the front end
.
• During this operation, as the frequency
varies, a smooth transition takes place
along the array of the elements, which
leads to form an active region.

9. 2. Wire Antennas
• Wire antennas are also known as linear o
r curved antennas. These antennas are
very simple, cheap and are used in a wid
e range of applications.

10. • These antennas are
further subdivided into four types
Short Dipole Antenna
Dipole Antenna
Monopole Antenna
Loop Antenna

11. Dipole Antenna
• The dipole antenna consists of two metall
ic rods through which current and voltag
e flow.
• This current and voltage flow makes an
electromagnetic wave and the radio
signals get radiated.
• This are mainly used in FM broadcasting.

12. Short Dipole Antenna
• It is the simplest of all types of antennas.
• This antenna is an open circuited wire in
which short denotes “ relative to a
wavelength”
• A Dipole is considered as short if the
length of the radiating element is less tha
n a tenth of the wavelength.
• L<λ/10
•

13. Monopole Antenna
• A monopole antenna is half of a simple
dipole antenna located over a grounded
plane.
• the total power radiated is half that of a
dipole.
• The directivity of these antennas become
double compared to the dipole antennas
.
GSM, Bluetooth, and UWB are main applications

14. Loop Antenna
A loop antenna is a closed circuit
radio antenna.
Loop antennas are available in differen
t shapes like circular, elliptical,
rectangular, etc.
They are widely used in communicatio
n links.

15. 3. Travelling Wave Antennas
• The antenna in which the standing wave
does not exist along the length of the
antenna is called traveling wave antenna.
• These antennas are of two types
1. Helical Antennas
2. Yagi-Uda Antennas

16. Helical Antennas
• Helical antennas are also known as helix
antennas.
• As it is a traveling wave antenna, the curren
t and phase vary continuously along the
helical antenna.
• Because of their unique and special
properties, helical antennas are widely used
in simple and practical applications such as
in radios and satellite communications.

17. Yagi-Uda Antennas
• A Yagi antenna, also known as a Yagi-Ud
a array or simply a Yagi, is a directional
antenna commonly used in communicati
on when a frequency is above 10 MHz.

18. 4. Microwave Antennas
• The antennas operating at microwave
frequencies are known as microwave
antennas.
• These antennas are used in a wide range
of applications.
• These antennas are classified into two
types
• Rectangular Micro strip Antennas
• Planar Inverted-F Antennas

19. 5. Reflector Antennas
• An antenna reflector is a device that reflec
telectromagnetic waves.
• These antennas are classified into two
types
• Corner Reflector Antenna
• Parabolic-Reflector Antenna

20. • Advantages of Antenna Types
•
➨Dipole Antenna:They are cheap and
exhibits good gain.
➨Loop Antenna:They are cheap and not
easily de-tuned by hand movements.
➨Helical Antenna: It is very directive
antenna and provides good amount of gai
n.
➨Microstrip Antenna:They are very simpl
e and chip antenna. They are used in smar
t phone due to their thin structure.

21. ANTENNA APPLICATIONS
• They are used in Radio Astronomy.
• antenna is used to cure breast cancer.
• Antennas can be extremely small. iPhone
has several antennas all built into that
small case.
• Mobile satellite communication
• Used in GPS tracking
• Antennas are also used in Remote
sensing and in defense radar.

22. largest antenna in the world
World's Largest Radio Telescope
Five-hundred-meter Aperture Spherical Telescope's (FAST) giant dish, China's state-run

23. world's smallest antenna
Developed by Indian scientist
Chakraborty, a PhD student