Microwaves Applications
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Transcript of Microwaves Applications
• Muhammad Umer Shehzad• Jawad Fakhir
• Sir Haissam Sattar
Introduction to MicrowavesProperties of MicrowavesAdvantages/Disadvantages of MicrowavesWaveguideApplications of MicrowavesMicrowave ovenRadarWireless Mobile ChargingOthers Applications
In physics, a wave is disturbance or oscillation that travels through matter or space, accompanied by a transfer of
energy.
There are two main types of waves.
Mechanical WavesElectromagnetic
Waves
• Radio waves• Microwaves• Infrared radiation• Visible light• Ultraviolet radiation
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Microwaves are electromagnetic waves
Frequency range 300MHz-300Ghz
Wavelengths range in air
100cm-1mm
The word microwave means “very short wave”
Microwaves is the shortest wavelength region of the radio
spectrum and a part of the
electromagnetic spectrum
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Microwaves Frequency Bands
Properties of Microwaves
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1.Electromagnetic radiation of short
wavelength
2.Can reflect by conducting surface like optical waves.
3.M.W current flows through outer layer
of conductor
4.Microwaves are easily attenuated
5.They are not reflected by ionosphere
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Microwaves have large bandwidths
Improved Directive properties.Can be
focused in a specified direction
Fading effect and reliability.
Due to LOS and high frequency fading effect is
very low
Transmitter/Receiver power requirements are pretty low at microwave
frequencies
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Microwave band ranging from 300MHz-10GHz are capable of freely propagating through atmosphere
This helps in astronomical research of space in the study of microwave radiations from
the sun and stars
Because of high frequency, more data can be sent.
High bandwidth,higher speeds
Because of their short wavelength,microwaves use
smaller antennas
Smaller antennas produce a
more focused beam
Functional Block Diagram of a Communication System
Input signal
(Audio, Video, Data)
Input TransducerTransmitter
Output TransducerReceiver
Output signal
(Audio, Video, Data)
Channel
Electrical System
Wire
or
Wireless
Antenna and Wave Propagation
Surface Wave
Direct Wave
Sky Wave
Satellitecommunication
Microwave & Millimeter Wave
Earth
Ionsphere
Transmitting Antenna
Receiving Antenna
Repeaters(Terrestrial communication)
50Km@25fts antenna
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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.
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Electromagnetic waves at frequencies greater than
3GHz; transmission through cables becomes difficult.
Reason
This is due to losses in the solid cable and the
dielectric use to support the cable.
So, we use waveguide which is a hollow
metallic
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Waveguides are used to carry energy from one equipment to
another
e.g. In Antennas transmitter power
to antenna and microwave signal from antenna to
receiver
Waveguides are made from copper, aluminum or brass
The metals are extruded into long
rectangular or circular pipes
The energy to be transmitted is injected from one end of the waveguide through probes
The electric and magnetic field of
signals bounce off the walls back and
forth.
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EM field configuration can be determined from Maxwell’s equation.
There are number of configurations and each configuration is known as mode.
Possible modes
TransverseElectromag
netic
Transverse Electric
Transverse Magnetic
Hybrid
Components of Electric and Magnetic Field Intensities in an EM wave
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O
X
Y
Z
Ex , Hx
Ez, Hz
E y,H y
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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
1.Transverse Electro Magnetic (TEM) wave:Here both electric and magnetic
fields are directed components.(i.e.) Ez=0 and Hz=0
2.Transverse Electric (TE) wave:The electric field component is
purely transverse to the direction of propagation.(i.e.) Ez=0 and Hz≠0
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3.Transverse Magnetic (TM) wave:The magnetic field component is
purely transverse to the direction of propagation.(i.e.) Ez≠0 and Hz=0
4.Hybrid (HE) wave:Here neither electric nor magnetic fields are
purely transverse to the direction of propagation.(i.e.) Ez≠0 and Hz≠0
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Rectangular Waveguides
Any shape of cross section of a waveguide can support electromagnetic waves of which rectangular and circular waveguides have become more common.
A waveguide having rectangular cross section is known as Rectangular waveguide
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Rectangular waveguide
Dimensions of the waveguide which determines the operating
frequency range
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1.The size of the waveguide determines its operating frequency
2.The frequency of operation is determined by dimension ‘a’ which is usually made one half the wavelength at lowest frequency of
operation.
3.At cutoff frequency and below, the waveguide will not transmit energy.
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Wave paths in a waveguide at various frequencies
Angle of incidence(A) Angle of reflection (B)
(A = B) (a) At high
frequency
(b) At medium
frequency
( c ) At low frequency
(d) At cutoff
frequency
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Wave propagation
When a probe launches energy into the waveguide, the electromagnetic fields bounce off the side walls of the waveguide as shown in the above diagram.
The angles of incidence and reflection depend upon the operating frequency. At high frequencies, the angles are large and therefore, the path between the opposite walls is relatively long as shown in Fig.
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At lower frequency, the angles decrease and the path between the sides
shortens.
When the operating frequency is reaches the cutoff frequency of the
waveguide, the signal simply bounces back and forth directly between the side
walls of the waveguide and has no forward motion.
At cut off frequency and below, no energy will propagate.
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• It is used for bends, twists or in applications where certain criteria may not be fulfilled by normal waveguides.
• Figure below shows some of the flexible waveguides:
How a Microwave Oven Works?
History
Invented Accidentally By Dr. Percy Lebaron Spencer.
Working Principle
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Microwave radiations generated by a magnetron pass through the exposed food, create dielectric heating within the food, this is the basic principle on which a microwave oven works.
Dielectric Heating
How the Oven Works
Electricity from the wall outlet travels through the power cord and enters the
microwave oven through a series of fuse and safety protection circuits
When the oven door is closed, an electrical path is also established through a series
of safety interlock switches
Sensing That All Systems Are Set To Go, The Signal Activates Triac Producing A Voltage Path
To The High-voltage Transformer.
The High-voltage Transformer Along With A Special Diode And Capacitor Arrangement
Increases The Typical Household Voltage From ~220 Volts To ~3000 Volts
The magnetron converts the high voltage into the microwave frequency for cooking.
The microwave energy is transmitted into a waveguide.
The waveguide feeds the energy to the stirrer blade and into the cooking area.
When the door is opened, or the timer reaches zero, the microwave energy stops.
How Foods Get Cooked
The microwaves that penetrate the food have an electric field that oscillates 2.45
billion times a second, a frequency that is well absorbed by polar liquid molecules
such as water, sugars, fats and other food molecules.
Water interacts with the microwave:
flipping its orientation back and forth very rapidly
bumping into one another and producing heat, cooking the food.
Radar
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Introduction
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Radar Radio Detection and Ranging
A System For Detecting The Presence, Direction, Distance, And Speed Of Aircraft, Ships, And Other Objects, By Sending Out Pulses Of Radio Waves Which Are Reflected Off The Object Back To The Source.
The Time Delay Between The Transmitted Pulse And The Received Echo Can Be Used To Determine The Distance To The Target .
Basic Principle and Operation Of Radar
RADAR FUNCTIONS
TRANSMITTER:
Generate radio waves
Perform modulation
Amplification to high power
RECIEVER:
High sensitivity
Very low noise
Ability to discern a received signal from background noise
PROCESSING & CONTROL:
It regulates the rate at which pulses are sent (PRF). Synchronizes the function between Transmitter, Receiver,
display, duplexer etc.
DUPLEXER:
A switch to alternatively connect Tx and Rx to antenna.
ANTENNA:
Takes radar pulses from transmitter and puts into the air.
Focuses energy into the well designed beam.
Antenna is of two types
1) Physically moving
2) Electronically steered
DISPLAY:
Display received information to the operator. It is of two types
1) PPI
Used for surface search and navigation
2) A-Scan
Used for gunfire control
MAIN TYPES OF RADAR
There are two main types of radar:
1)Primary Radar
Continuous wave Radar
Pulse Radar
2)Secondary Radar SSR
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1)CONTINUOS WAVE RADAR:
Employs continual RADAR transmission
Separate transmit and receive antennas
Relies on the “DOPPLER SHIFT”
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2)PULSE RADAR:
The PULSE radar is the more conventional radar, which transmits a burst of radar energy and then waits for the energy (or echo) to be reflected back to the antenna.
Since radar waves travel at the speed of light, range from the return can be calculated.
Applications of Radar
MILITARY
Target Detection, Target Tracking & Weapon Control
Tracks The Targets, Directs The Weapon To An Intercept And Assess The Effectiveness Of Engagement
Weather Observation
Planetary Observation
Below Ground Probing
REMOTE SENSING
Used To Safely Control Air Traffic In The Vicinity Of The Airports.
Mapping Of Regions Of Rain In The Vicinity Of Airports & Weather.
AIR TRAFFIC CONTROL
Radar Speed Meters Are Used By Police For Enforcing Speed Limit.
LAW ENFORCEMENT & HIGHWAY SAFETY
• Airborne Weather Avoidance Radar Outlines The Regions Of Precipitation & Dangerous Wind Shear
• Low Flying Military Aircrafts Rely On Terrain Avoidance & Terrain Following Radars To Avoid Collision With High Terrain & Obstructions
AIRCRAFT SAFETY & NAVIGATION
• Radar Is Found On Ships & Boats For Collision Avoidance & To Observe Navigation Buoys, When The Visibility Is Poor
• Shore Based Radars Are Used For Surveillance Of Harbours & River Traffic
SHIP SAFETY
• Space Vehicles Have Used Radar For Landing On The Moon And Other Planets.
• Used For Planetary Exploration
• Ground Based Radars Are Used For Detection & Tracking Of Satellites & Other Space Objects
• Used For Radio Astronomy
SPACE
MINE INSPECTION
LOCATING UNDER GROUND PIPES
Wireless Charging of Mobile Phones Using Microwaves
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INTRODUCTION Objective—to Recharge Any Mobile Phone Independent Of Particular Mobile
Charger.
Mobile Phones Becoming Basic Part Of Life
Recharging Of Mobile Phones Is A Big Problem
More You Talk More The Mobile Get Charged!
No Separate Mobile Charger
Additives To Mobile Handsets:
Sensor
Rectenna
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Microwave region of electromagnetic spectrum
We choose s –band of microwave region(2-4GHz)
We Use License free 2.45 GHz Industrial, Scientific and Medical (ISM)
radio bands
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Designation Frequency range
L Band 1 to 2 GHz
S Band 2 to 4 GHz
C Band 4 to 8 GHz
X Band 8 to 12 GHz
Ku Band 12 to 18 GHz
K Band 18 to 26 GHz
Ka Band 26 to 40 GHz
Q Band 30 to 50 GHz
U Band 40 to 60 GHz
Principle of Operation &
Block Diagram
Transmitting station with the
microwave transmitter
sensor
Rectenna
RF cable
circulator
waveguide
Slotted waveguideAntenna
mobile signal
Microwave signal is transmitted from transmitter along with message signal using slotted waveguide antenna at frequency 2.45 GHZ.
The sensor search for the mobile signal , in addition it has a “RECTENNA”.
Rectenna receives the transmitted power and converts the microwave power to DC power.
TRANSMITTER SECTION
Consists of two parts
Magnetron
Slotted waveguide antenna
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MAGNETRON
• Magnetron is a vacuum tube oscillator that generates
high-power electromagnetic signals in the microwave
frequency range.
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Working Principle
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When a charge/charge particle accelerates in space, it generates electromagnetic waves.
This statement is the derivation of Maxwell’s law which says that a classical electromagnetic radiation is ultimately generated when a charged particle is accelerated through space.
Working
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Slotted waveguide antenna
It is an Omni-directional Antenna.
It is used as ideal power transmitter
(because of its high aperture efficiency
>95%) .
It has high power handling capacity .
RECEIVER SECTION
Basic additions to mobile phone
Sensor
Rectenna
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SENSOR Simple circuit which detects whether the user is making a call
Simple F to V converter, this would serve our purpose
Operating frequency of mobile phone operators for GSM system for mobile
communication in Pakistan is 900MHZ to 1800MHZ
Simple yet powerful F to V converter is LM2907
On the reception of the microwave signal ,the sensor circuitry directs rectenna circuit to
ON
Rectenna circuit converts microwave energy to dc output
Mobile phone begins to charge using the microwave power as long as the user talks over
cell phone.
RECTENNA A rectifying antenna called a rectenna receives the transmitted power
and converts the microwave power to direct current (DC) power.
The Schottky diode rectifies the AC current induced in the antenna by the microwaves, to produce DC power, which powers a load connected across the diode.
Schottky diodes are usually used because they have the lowest voltage drop and highest speed and therefore have the lowest power losses due to conduction and switching.
Circuit Design
Implementation
Recently NOKIA has launched this wireless charging technology
in its new recent mobile model “ NOKIA LUMIA 1020”.
Advantages
The need of different types of chargers by different
manufacturers is totally eliminated
Lower risk of ELECTRICAL SHOCK or shorting.
Convenience.
Get Charged as we make call.
Only one microwave transmitter can serve to all the
service providers in that area.
Disadvantages
Wireless transmission of the energy causes some
drastic effects to human body, because of its radiation.
Process is of high cost.
Network Traffic may Cause Problem in charging
Other Applications Of Microwaves
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Homeland Security Applications
Potential Security Applications
Detection of hidden weapons and explosives
Detecting non-metallic weapons
Postal screening of envelopes for bacteria
Chem/bio detection
Security screening wand
Explosives
Stand-off detection
Postal screening
Envelope
Terahertz Images Can Reveal Objects Concealed Under Cloth, Paper, Tape, Even Behind Walls
Objects Concealed Under clothes Knife Wrapped in Newspaper
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