Microwaves 1 s

8/12/2019 Microwaves 1 s

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Muhammad Umer Shehzad

Jawad Fakhir

Sir Haissam Sattar


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In physics, a waveis 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 air100cm-

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


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Properties of Microwaves

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1.Electromagnetic

radiation of shortwavelength

2.Can reflect by

conducting surfacelike optical waves.

3.M.W current flows

through outer layerof conductor

4.Microwaves are

easily attenuated

5.They are not

reflected byionosphere


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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 highfrequency fading effect is

very low

Transmitter/Receiver

power requirements are

pretty low at microwavefrequencies


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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


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Because of high frequency,

more data can be sent.

High

bandwidth,hi

gher speeds

Because of their short

wavelength,microwaves use

smaller antennas

Smaller

antennasproduce a

more focused

beam


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Functional Block Diagram of aCommunication System

Input signal

(Audio, Video, Data)

Input TransducerTransmitter

Output TransducerReceiver

Output signal

(Audio, Video, Data)

Channel

Electrical System

Wire

or

Wireless


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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 transmittingelectromagnetic 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 toanother

e.g. In Antennas

transmitter power

to antenna and

microwave signalfrom antenna to

receiver

Waveguides are made from copper,

aluminum or brass

The metals areextruded into long

rectangular or

circular pipes

The energy to be transmitted is

injected from one end of the

waveguide through probes

The electric andmagnetic field of

signals bounce off

the walls back and

forth.


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EM field configuration can be determined from

Maxwells equation.

There are number of configurations and each

configuration is known as mode.

Possible

modes

Transverse

Electromag

netic

Transverse

Electric

Transverse

MagneticHybrid


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Components of Electric and Magnetic

Field Intensities in an EM wave

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O

X

Y

Z

Ex, H

x

Ez, Hz

Ey,

Hy


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2. Transverse Electric (TE) wave:Here only the electric field ispurely transverse to the direction of propagation and the magnetic

field is not purely transverse. (i.e.) Ez= 0, H

z 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 Hz0


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3.Transverse Magnetic (TM) wave:The magnetic field component is

purely transverse to the direction of propagation.(i.e.) Ez0 and Hz=0

4.Hybrid (HE) wave:Here neither electric nor magnetic fields are

purely transverse to the direction of propagation.(i.e.) Ez0 and Hz0


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Rectangular Waveguides

Any shape of cross section of a waveguidecan support electromagnetic waves ofwhich rectangular and circular waveguides

have become more common.

A waveguide having rectangular crosssection is known as Rectangularwaveguide


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Rectangular waveguide

Dimensions of the waveguide which determines the operatingfrequency range


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1.The size of the waveguide determines its

operating frequency

2.The frequency of operation is determinedby 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 propagation

When a probe launches energy into thewaveguide, the electromagnetic fields bounceoff the side walls of the waveguide as shown inthe above diagram.

The angles of incidence and reflection dependupon the operating frequency. At highfrequencies, the angles are large and therefore,

the path between the opposite walls is relativelylong 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 thewaveguide, 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 befulfilled by normal waveguides.

Figure below shows some of the flexible waveguides:


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How a Microwave Oven Works?


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History

Invented Accidentally By Dr. Percy Lebaron Spencer.


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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


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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


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Sensing That All Systems Are Set To Go, The Signal Activates Triac Producing A Voltage PathTo 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


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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.


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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 BeUsed To Determine The Distance To The Target .


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Basic Principle and Operation Of Radar


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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


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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


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MAIN TYPES OF RADAR

There are two main types of radar:

1)Primary Radar

Continuous wave Radar

Pulse Radar

2)Secondary Radar SSR

1)CONTINUOS WAVE RADAR


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1)CONTINUOS WAVE RADAR:

Employs continual RADAR transmission

Separate transmit and receive antennas

Relies on the DOPPLER SHIFT

2)PULSE RADAR:


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2)PULSE RADAR:

The PULSE radar is the more conventional radar, which transmits aburst of radar energy and then waits for the energy (or echo) to bereflected back to the antenna.

Since radar waves travel at the speed of light, range from the return canbe calculated.

Applications of Radar


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Applications of Radar


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MILITARY

Target Detection, Target Tracking & Weapon Control

Tracks The Targets, Directs The Weapon To An Intercept And Assess

The Effectiveness Of Engagement


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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


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Radar Speed Meters Are Used By Police For EnforcingSpeed Limit.

LAW ENFORCEMENT &HIGHWAY SAFETY


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Airborne Weather Avoidance Radar Outlines The RegionsOf Precipitation & Dangerous Wind Shear

Low Flying Military Aircrafts Rely On Terrain Avoidance &Terrain Following Radars To Avoid Collision With HighTerrain & Obstructions

AIRCRAFT SAFETY &

NAVIGATION


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Radar Is Found On Ships & Boats For Collision Avoidance & ToObserve Navigation Buoys, When The Visibility Is Poor

Shore Based Radars Are Used For Surveillance Of Harbours &

River Traffic

SHIP SAFETY


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MINE INSPECTION


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LOCATING UNDER GROUND PIPES

W


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Wireless Charging of Mobile

Phones Using Microwaves

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INTRODUCTION


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INTRODUCTION Objectiveto 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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Micro a e region of


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Micro a e region ofelectromagnetic spectrum

We choose sband 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 GHzC Band 4 to 8 GHz

X Band 8 to 12 GHz

Ku Band 12 to 18 GHz

K Band 18 to 26 GHzKa Band 26 to 40 GHz

Q Band 30 to 50 GHz

U Band 40 to 60 GHz

Principle of Operation &


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Principle of Operation &

Block Diagram

Transmitting

station with the

microwave

transmitter

sensor

Rectenna

RF cable

circulator

waveguide

Slotted waveguide

Antenna

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 aRECTENNA.

Rectenna receives the transmitted power and converts the

microwave power to DC power.


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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


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Slotted a eg ide antenna


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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 .


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RECEIVER SECTION

Basic additions to mobile phone

Sensor

Rectenna

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SENSOR


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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 toON

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.


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Implementation


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Implementation

Recently NOKIA has launched this wireless charging technology

in its new recent mobile model NOKIA LUMIA 1020.


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Advantages

The need of different types of chargers by differentmanufacturers 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 theservice providers in that area.

Di d t


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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


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Other Applications Of Microwaves

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Homeland Security Applications


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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


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Under Cloth, Paper, Tape, Even Behind Walls

Objects Concealed Under clothes Knife Wrapped in Newspaper


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Microwaves 1 s

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