UNIT I introduces microwave systems and antennas. It discusses microwave frequency bands from 1 GHz to 300 GHz and key antenna concepts like near and far fields, gain, efficiency, impedance matching, and the Friis transmission equation. The unit also covers antenna pattern characteristics, radiated power and fields, and antenna noise temperature. UNIT I provides an overview of key topics in microwave engineering and antenna fundamentals, including microwave frequency bands, antenna radiation mechanisms, near and far-field regions, antenna parameters like gain and pattern characteristics, impedance matching concepts, and noise modeling of microwave systems.

1. UNIT-1
EC8701 - ANTENNAS AND
MICROWAVE ENGINEERING

2. All the truths are easy to understand once they are discovered;
The point is to discover them
- Galileo Galilei

3. EC8701 ANTENNAS AND MICROWAVE ENGINEERING
OBJECTIVES:
• To enable the student to understand the basic principles in antenna and microwave
system design
• To enhance the student knowledge in the area of various antenna designs.
• To enhance the student knowledge in the area of microwave components and antenna for practical
applications.
UNIT I INTRODUCTION TO MICROWAVE SYSTEMS AND ANTENNAS
Microwave frequency bands, Physical concept of radiation, Near- and far-field regions, Fields and
Power Radiated by an Antenna, Antenna Pattern Characteristics, Antenna Gain and Efficiency,
Aperture Efficiency and Effective Area, Antenna Noise Temperature and G/T, Impedance matching,
Friis transmission equation, Link budget and link margin, Noise Characterization of a microwave
receiver.
UNIT II RADIATION MECHANISMS AND DESIGN ASPECTS
Radiation Mechanisms of Linear Wire and Loop antennas, Aperture antennas, Reflector antennas,
Microstrip antennas and Frequency independent antennas, Design considerations and applications.

4. UNIT III ANTENNAARRAYS AND APPLICATIONS
Two-element array, Array factor, Pattern multiplication, Uniformly spaced arrays with uniform and non-
uniform excitation amplitudes, Smart antennas.
UNIT IV PASSIVE AND ACTIVE MICROWAVE DEVICES
Microwave Passive components: Directional Coupler, Power Divider, Magic Tee, attenuator, resonator,
Principles of Microwave Semiconductor Devices: Gunn Diodes, IMPATT diodes Schottky Barrier
diodes, PIN diodes, Microwave tubes: Klystron, TWT, Magnetron.
UNIT V MICROWAVE DESIGN PRINCIPLES
Impedance transformation, Impedance Matching, Microwave Filter Design, RF and Microwave
Amplifier Design, Microwave Power amplifier Design, Low Noise Amplifier Design, Microwave Mixer
Design, Microwave Oscillator Design

5. What is an Antenna?
Student responses…

6. Definition:
• A radio antenna may be defined as the structure associated with the region of
transition between a guided wave and a free-space wave or vice versa.
• The antennas radiate or receive energy, transmission lines guide energy and
resonators store energy.
• An Antenna is a transducer, which converts electrical power into electromagnetic
waves and vice versa.
• An Antenna can be used either as a transmitting antenna or a receiving antenna.
• A transmitting antenna is one, which converts electrical signals into
electromagnetic waves and radiates them.
• A receiving antenna is one, which converts electromagnetic waves from the
received beam into electrical signals eg. eye.
• In two-way communication, the same antenna can be used for both transmission
and reception.

7. Why we need Antenna?
A person, who needs to convey a thought, an idea or a doubt, can do so
by voice communication.
When two individuals communicating with each other. Here, communication
takes place through sound waves. However, if two people want to
communicate who are at longer distances, then we have to convert these
sound waves into electromagnetic waves. The device, which converts the
required information signal into electromagnetic waves, is known as
an Antenna.

8. UNIT I:INTRODUCTION TO MICROWAVE SYSTEMS
AND ANTENNAS
• Microwaves are electromagnetic waves (EM) with wavelengths ranging from
1cm to 1m. The corresponding frequency range is 1 GHz to 300 GHz ( 1GHz =
109𝐻𝑧). This means microwave frequencies are upto infrared and visible – light
regions.
L-band 1000 - 2000 MHz
S-band 2000 - 4000MHz
SHF 3 GHz - 30 GHz (Super High Frequency) ITU Band 10
C-band 4000-8000MHz
X-band 8-12 GHz
Ku-band 12GHz-18 GHz
K-band 18 GHz-27 GHz
EHF 30 GHz - 300 GHz (Extremely High Frequency) ITU Band 11
Ka-band 27-40 GHz Millimeter Wave Frequencies
V-band 40-75 GHz
1. Microwave Frequency Bands

9. Microwave Frequency Bands
ELF SLF ULF /
VF
VLF LF MF HF VHF UHF SHF EHF
3-30
Hz
30 Hz-300
Hz
300 Hz
-3000
Hz
3-30
KHz
30-300
KHz
300
KHz - 3
MHz
3MHz-
30MHz
30MHz-
300MH
z
300MHz
-3GHz
3 GHz -
30 GHz
30 GHz
- 300
GHz
https://donsnotes.com/tech/em-spectrum.html
INFRARED VISIBLE
LIGHT
ULTRA
VIOLET
X RAYS Y GAMMA
RAYS
COSMIC
RAYS
100 GHz - 500
THz
500 THz - 900
THz
750x𝟏𝟎𝟏𝟐
Hz
(THz) - 30x
𝟏𝟎𝟏𝟓
Hz (PHz)
30x𝟏𝟎𝟏𝟖
EHz 30x𝟏𝟎𝟏𝟖
-
𝟏𝟎𝟐𝟖 Hz
30x𝟏𝟎𝟏𝟖
(EHz)- 𝟏𝟎𝟐𝟖
Hz

10. ELF : 3-30 Hz(Extremely Low Frequency) Metal Detectors
SLF : 30 Hz-300 Hz(Super Low Frequency) Submarine communications
ULF or VF 300 Hz-3000 Hz(Ultra Low Frequency/Voice Frequency)
Audio - Telephone
VLF 3-30 KHz(Very Low Frequency)
Navigation, Sonar
LF 30-300 KHz(Low Frequency)
9-190 KHz Radio navigation and Maritime
190-405 KHz Aeronautical and Radio Beacons
https://donsnotes.com/tech/em-spectrum.html
MF 300 KHz - 3 MHz (Medium Frequency)
AM Radio 535 - 1705 KHz Police, Fire
2000-2187 Maritime radio, Direction finding
457 KHz Avalanche Beacon
1800-2000 KHz 160 m amateur radio
2300-2500 120 m Shortwave BCB International Radio

11. HF 3MHz-30MHz (High Frequency) ITU Band 7
VHF 30MHz-300MHz (Very High Freq.) ITU Band 8
UHF 300MHz-3GHz (Ultra High Freq.) ITU Band 9 328-335 Aeronautical Radio navigation
Microwave 1 GHz - 300 GHz
L-band 1000 - 2000 MHz (LONG)
S-band 2000 - 4000MHz (short)
SHF 3 GHz - 30 GHz (Super High Frequency) ITU Band 10
C-band 4000-8000MHz (conventional)
https://donsnotes.com/tech/em-spectrum.html
X-band 8-12 GHz
Ku-band 12GHz-18 GHz
K-band 18 GHz-27 GHz (krus –short-in German)
EHF 30 GHz - 300 GHz (Extremely High Frequency) ITU Band 11
Ka-band 27-40 GHz Millimeter Wave Frequencies
V-band 40-75 GHz
W-band 75-110 GHz

12. Beyond Radio Frequency
At 300GHz the wave length is 0.1 mm and the em energy starts to behave more like particles than waves.
( EM energy has properties of both waves and particles or quanta of energy.)
Infrared 100 GHz - 500 THz
Visible 500 THz - 900 THz
Ultraviolet 750x𝟏𝟎𝟏𝟐
Hz (THz) - 30x 𝟏𝟎𝟏𝟓
Hz (PHz)
X-Rays 30x1015 PHZ - 30x𝟏𝟎𝟏𝟖 EHz
Y Gamma rays 30x𝟏𝟎𝟏𝟖 - 𝟏𝟎𝟐𝟖 Hz
Cosmic rays 30x𝟏𝟎𝟏𝟖 (EHz)- 𝟏𝟎𝟐𝟖 Hz
https://donsnotes.com/tech/em-spectrum.html

13. RADIO FREQUENCY BANDS

15. Applications of Microwave
• Communication
• Terrestrial –
• Microwave links
• Cellular
• Wlan
• Satellite
• RADAR
• Civilian
• Air traffic
• Ship traffic control
• Car traffic control
• Remote sensing
• Military
• Surveillance
• Navigation
• Weapon guidance
• Electronic warfare

16. Applications of Microwaves
• Industrial and Commercial
• Heating
• Drying
• Waste treatment
• Sensing and monitoring
• Biomedical
• Hypothermia
• Imaging
• Microwave spectroscopy

29. A guided wave travelling along a transmission line which opens out, as in the figure will radiate as a free-
space wave. The guided wave is a plane wave while the free-space wave is a spherically expanding wave.
Along the uniform part of the line, energy is guided as a plane wave with little loss, provided the spacing
between the wires is a small fraction of a wavelength.

30. Antenna Radiation and Reception
Dipole radiation fields:
Electric field (blue)
Magnetic field (red)
(picture from wikipedia)
Due to absence of transmission line conductors, the field lines join
is generated with spherical wave
together and an electromagnetic wave
front whose source is the signal generator connected at the input end.

31. • A transmission line is a device for transmitting or guiding radio frequency
energy from one point to another. It is desirable to transmit the energy
with a minimum of attenuation, heat and radiation losses being as small as
possible.
• The wave transmitted along the line is 1 dimensional in that it does not
spread into space but follows along the line.
• The region of transition between the guided wave and the free-space wave
is defined as an antenna.
• The antenna, like the eye, is a transformation device converting
electromagnetic photons into circuit currents; but unlike the eye, the
antenna can also convert energy from a circuit into photons radiated into
space.

32. Need of Antenna
In the field of communication systems, whenever the need for wireless
communication arises, there occurs the necessity of an antenna. Antenna has
the capability of sending or receiving the electromagnetic waves for the sake of
communication, where you cannot expect to lay down a wiring system.
Scenario
In order to contact a remote area, the wiring has to be laid down throughout
the whole route along the valleys, the mountains, the tedious paths, the
tunnels etc., to reach the remote location. The evolution of wireless
technology has made this whole process very simple. Antenna is the key
element of this wireless technology.

33. Antenna from Transmission Lines
• A transmission-line Thevenin equivalent of the antenna system in the transmitting mode is shown, where the
source is represented by an ideal generator, the transmission line is represented by a line with characteristic
impedance Zo and the antenna is represented by a load ZA [ZA= (RL + Rr) + jXA ] connected to the transmission
line.
• The load resistance RL is used to represent the conduction and dielectric losses associated with the antenna
structure while Rr, referred to as the radiation resistance, is used to represent radiation by the antenna. The
reactance XA is used to represent the imaginary part of the impedance associated with radiation by the antenna.

34. • Under ideal conditions, energy generated by the source should be totally transferred to the radiation
resistance R, which is used to represent radiation by the antenna.
• The reflected waves from the interface create, along with the traveling waves from the source
toward the antenna, constructive and destructive interference patterns, referred to as standing
waves, inside the transmission line which represent pockets of energy concentrations and
storage, typical of resonant devices.
• If the antenna system is not properly designed, the transmission line could act to a large degree as
an energy storage element instead of as a wave guiding and energy transporting device. If the
maximum field intensities of the standing wave are sufficiently large, they can cause arching
inside the transmission lines.
The standing waves can be reduced, and the energy storage capacity of the
line minimized, by matching the impedance of the antenna (load) to the
characteristic impedance of the line. This is the same as matching loads to
transmission lines, where the load here is the antenna

35. Load impedance and feeder impedance

43. • https://www.walter-fendt.de/html5/phde/standingwavereflection_de.htm