It is a hectic task to carry everywhere the charger of mobile phones or any electronic gadget while travelling, or it is very cruel when your mobile phone getting off by the time you urgently need it. It is the major problem in today’s electronic gadgets. Though the world is leading with the developments in technology, but this technology is still incomplete because of these limitations. Today’s world requires the complete technology and for this purpose here we are proposing the wireless charging of batteries using Microwaves. Now in the recent days we come across some solutions for this problem by using the Witricity (Wireless Transmission of Electricity). Recently Nokia has launched Nokia Lumia 920 smart phones whose special feature is its wireless charging. But this is possible only when the device is placed on to the plate given for the wireless charging. So it is also somewhat difficult to travel with those charging plates. There may chance has forgetting the charging plates, and then we require something which can charge our electronic gadgets whenever they get used The proposed method gives the solution for this problem. Once think that how it will be when your electronic gadget gets charged on using it? Then the label will come as “CHARGE ON USE”. This wireless charging method works on the principle of MICROWAVE OVEN. As the things when placed in microwave oven gets heated, in the same way these batteries should work using microwaves which are the medium of communication from long back. We are getting our network in terms of microwaves and it is proved that the total radiation coming from the cellular mobile communication is not been using and the remaining radiation is creating hazardous problem for human beings. So here we are working on the concept that why can’t we use those remaining radiations in order to charge our batteries? This will be the best solution to reduce the effect of radiation.

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ACKNOWLEDGEMENT
I express my deep sense of gratitude to Malabar Polytechnic Campus that provided me the required
infrastructure in fulfilling my most cherished desire of reaching the goal.
I am also thankful to our principal Mr. Abdul Kareem who is responsible for creating such a pleasant
environment and appreciating my talents in both academic and extracurricular activities.
I would like to express my sincere thanks to Mr. Mohamed Thahir.PK,Lecturer and HOD of Elec-
trical and Electronics Engineering for his continuous support, advice and guidance.
I would like to express my sincere thanks to our guide Ms. Vimitha.P, for her continuous support,
advice and guidance.
I would like to express my gratitude to the teaching and non-teaching staff of Malabar Polytechnic
Campus Last but not the least I would like to thank my parents for their encouragement and never
ending support.
MOHAMMED JISHID. K.M
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Contents
1 ABSTRACT 4
2 INTRODUCTION 5
2.1 ELECTRO MAGNETIC SPECTRUM . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 WIRELESS POWER TRANSMISSION 8
3.1 WIRELESS POWER TRANSMISSION SYSTEM . . . . . . . . . . . . . . . . . . 8
3.2 MICROWAVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4 COMPONENTS OF POWER TRANSMISSION SYSTEM 10
4.1 MICROWAVE GENERATOR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.2 TRANSMITTING ANTENNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4.3 RECTENNA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5 WIRELESS POWER TRANSMISSION 12
6 SYSTEM DESIGN 13
6.1 TRANSMITTER SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
6.1.1 The Magnetron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.1.2 Slotted wave guide antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.2 RECIEVER SECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2.1 sensor circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2.2 Rectenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.2.3 Process of Rectification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.2.4 Schottky Barrier Diode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
7 INDUCTIVE CHARGING 20
8 ADVANTAGE 21
9 DISADVANTAGES 22
10 CONCLUSION 23
11 REFERENCE 24
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List of Figures
2.1 A Microwave Telecommunications Tower on Wrights Hill in Wellington, New Zealand 5
2.2 Electromagnetic spectrum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
4.1 Block Diagram of a Rectenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1 Block diagram of Wireless power transmission for Mobile phones . . . . . . . . . . 12
6.1 Magnetron . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
6.2 Slotted Waveguide Antenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.3 Zener regulated frequency to voltage converter . . . . . . . . . . . . . . . . . . . . . 16
6.4 Rectenna . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1 Existing Power Transfer system . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
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Chapter 1
ABSTRACT
It is a hectic task to carry everywhere the charger of mobile phones or any electronic gadget while
travelling, or it is very cruel when your mobile phone getting off by the time you urgently need it. It is
the major problem in today’s electronic gadgets. Though the world is leading with the developments
in technology, but this technology is still incomplete because of these limitations. Today’s world re-
quires the complete technology and for this purpose here we are proposing the wireless charging of
batteries using Microwaves.
Now in the recent days we come across some solutions for this problem by using the Witricity (Wire-
less Transmission of Electricity). Recently Nokia has launched Nokia Lumia 920 smart phones whose
special feature is its wireless charging. But this is possible only when the device is placed on to the
plate given for the wireless charging. So it is also somewhat difficult to travel with those charging
plates. There may chance has forgetting the charging plates, and then we require something which
can charge our electronic gadgets whenever they get used
The proposed method gives the solution for this problem. Once think that how it will be when your
electronic gadget gets charged on using it? Then the label will come as “CHARGE ON USE”. This
wireless charging method works on the principle of MICROWAVE OVEN. As the things when placed
in microwave oven gets heated, in the same way these batteries should work using microwaves which
are the medium of communication from long back. We are getting our network in terms of mi-
crowaves and it is proved that the total radiation coming from the cellular mobile communication is
not been using and the remaining radiation is creating hazardous problem for human beings. So here
we are working on the concept that why can’t we use those remaining radiations in order to charge
our batteries? This will be the best solution to reduce the effect of radiation.
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Chapter 2
INTRODUCTION
Microwaves are radio waves (a form of electromagnetic radiation) with wavelengths ranging from as
long as one meter to as short as one millimeter. The prefix micro- in microwave is not meant to suggest
a wavelength in the micrometer range. It indicates that microwaves are small compared to waves
used in typical radio broadcasting, in that they have shorter wavelengths. Microwave technology
Figure 2.1: A Microwave Telecommunications Tower on Wrights Hill in Wellington, New Zealand
is extensively used for point-to-point telecommunications (i.e., non-broadcast uses). Microwaves are
especially suitable for this use since they are more easily focused into narrow beams than radio waves,
allowing frequency reuse; their comparatively higher frequencies allow broad bandwidth and high
data transmission rates, and antenna sizes are smaller than at lower frequencies because antenna size
is inversely proportional to transmitted frequency. Microwaves are used in spacecraft communication,
and much of the world’s data, TV, and telephone communications are transmitted long distances by
microwaves between ground stations and communications satellites. Microwaves are also employed
in microwave ovens and in radar technology.With mobile phones becoming a basic part of life, the
recharging of mobile phone batteries has always been a problem. The mobile phones vary in their talk
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time and battery standby according to their manufacturer and batteries. All these phones irrespective
of their manufacturer and batteries have to be put to recharge after the battery has drained out. The
main objective of this current proposal is to make the recharging of the mobile phones independent
of their manufacturer and battery make. In this paper a new proposal has been made so as to make
the recharging of the mobile phones is done automatically as you talk in your mobile phone! This
is done by use of microwaves. The microwave signal is transmitted from the transmitter along with
the message signal using special kind of antennas called slotted wave guide antenna at a frequency is
2.45 GHz.
2.1 ELECTRO MAGNETIC SPECTRUM
To start with, to know what a spectrum is: when white light is shone through a prism it is separated out
into all the colors of the rainbow; this is the visible spectrum. So white light is a mixture of all colors.
Black is NOT a color; it is what you get when all the light is taken away. Some physicists pretend
that light consists of tiny particles which they call photons. They travel at the speed of light (what
a surprise). The speed of light is about 300,000,000 meters per second. When they hit something
they might bounce off, go right through or get absorbed. What happens depends a bit on how much
energy they have. If they bounce off something and then go into your eye you will "see" the thing
they have bounced off. Some things like glass and Perspex will let them go through; these materials
are transparent. Black objects absorb the photons so you should not be able to see black things: you
will have to think about this one. These poor old physicists get a little bit confused when they try
to explain why some photons go through a leaf, some are reflected, and some are absorbed. They
say that it is because they have different amounts of energy. Other physicists pretend that light is
made of waves. These physicists measure the length of the waves and this helps them to explain what
happens when light hits leaves. The light with the longest wavelength (red) is absorbed by the green
stuff (chlorophyll) in the leaves. So is the light with the shortest wavelength (blue). In between these
two colors there is green light, this is allowed to pass right through or is reflected. (Indigo and violet
have shorter wavelengths than blue light.) Well it is easy to explain some of the properties of light
by pretending that it is made of tiny particles called photons and it is easy to explain other properties
of light by pretending that it is some kind of wave. The visible spectrum is just one small part of the
electromagnetic spectrum. These electromagnetic waves are made up of to two parts. The first part is
an electric field. The second part is a magnetic field. So that is why they are called electromagnetic
waves. The two fields are at right angles to each other.
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Figure 2.2: Electromagnetic spectrum
Volumetric heating, as used by microwave ovens, transfers energy through the material electro-
magnetically, not as a thermal heat flux. The benefit of this is a more uniform heating and reduced
heating time; microwaves can heat material in less than 1 percentage of the time of conventional heat-
ing methods.
When active, the average microwave oven is powerful enough to cause interference at close range
with poorly shielded electromagnetic fields such as those found in mobile medical devices and poorly
made consumer electronics.]The super-high frequency (SHF) and extremely high frequency (EHF)
of microwaves are on the short side of radio waves. Microwaves are waves that are typically short
enough (measured in millimeters) to employ tubular metal waveguides of reasonable diameter. Mi-
crowave energy is produced with klystron and magnetron tubes, and with solid state diodes such as
Gunn and IMPATT devices. Microwaves are absorbed by molecules that have a dipole moment in
liquids. In a microwave oven, this effect is used to heat food. Low-intensity microwave radiation is
used in Wi-Fi, although this is at intensity levels unable to cause thermal heating.
Volumetric heating, as used by microwave ovens, transfers energy through the material electro-
magnetically, not as a thermal heat flux. The benefit of this is a more uniform heating and reduced
heating time; microwaves can heat material in less than 1 percentage of the time of conventional heat-
ing methods.
When active, the average microwave oven is powerful enough to cause interference at close range
with poorly shielded electromagnetic fields such as those found in mobile medical devices and poorly
made consumer electronics.
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Chapter 3
WIRELESS POWER TRANSMISSION
Wireless power transfer (WPT) or wireless energy transmission is the transmission of electrical power
from a power source to a consuming device without using solid wires or conductors. It is a generic
term that refers to a number of different power transmission technologies that use time-varying elec-
tromagnetic fields. Wireless transmission is useful to power electrical devices in cases where in-
terconnecting wires are inconvenient, hazardous, or are not possible. In wireless power transfer, a
transmitter device connected to a power source, such as the mains power line, transmits power by
electromagnetic fields across an intervening space to one or more receiver devices, where it is con-
verted back to electric power and utilized.
Wireless power techniques fall into two categories, non-radiative and radiative. In near-field or
non-radiative techniques, power is transferred over short distances by magnetic fields using inductive
coupling between coils of wire or in a few devices by electric fields using capacitive coupling between
electrodes. Applications of this type are electric toothbrush chargers, RF-ID tags, smart cards, and
chargers for implantable medical devices like artificial cardiac pacemakers, and inductive powering
or charging of electric vehicles like trains or buses. A current focus is to develop wireless systems
to charge mobile and hand held computing devices such as cellphones, digital music players and
portable computers without being tethered to a wall plug.
In radiative or far-field techniques, also called power beaming, power is transmitted by beams of
electromagnetic radiation, like microwaves or laser beams. These techniques can transport energy
longer distances but must be aimed at the receiver. Proposed applications for this type are solar power
satellites, and wireless powered drone aircraft. An important issue associated with all wireless power
systems is limiting the exposure of people and other living things to potentially injurious electromag-
netic fields.
3.1 WIRELESS POWER TRANSMISSION SYSTEM
William C. Brown, the pioneer in wireless power transmission technology, has designed, developed a
unit and demonstrated to show how power can be transferred through free space by microwaves. The
concept of Wireless Power Transmission System is explained with functional block diagram shown
in Figure 2. In the transmission side, the microwave power source generates microwave power and
the output power is controlled by electronic control circuits. The wave guide ferrite circulator which
protects the microwave source from reflected power is connected with the microwave power source
through the Coax – Wave-guide Adapter. The tuner matches the impedance between the transmit-
ting antenna and the microwave source. The attenuated signals will be then separated based on the
direction of signal propagation by Directional Coupler. The transmitting antenna radiates the power
uniformly through free space to the rectenna. In the receiving side, a rectenna receives the transmitted
power and converts the microwave power into DC power. The impedance matching circuit and filter
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is provided to setting the output impedance of a signal source equal to the rectifying circuit. The
rectifying circuit consists of Schottky barrier diodes converts the received microwave power into DC
power.
3.2 MICROWAVES
Power transmission via radio waves can be made more directional, allowing longer distance power
beaming, with shorter wavelengths of electromagnetic radiation, typically in the microwave range.
A rectenna may be used to convert the microwave energy back into electricity. Rectenna conversion
efficiencies exceeding 95 percentage have been realized. Power beaming using microwaves has been
proposed for the transmission of energy from orbiting solar power satellites to Earth and the beaming
of power to spacecraft leaving orbit has been considered.
Power beaming by microwaves has the difficulty that, for most space applications, the required
aperture sizes are very large due to diffraction limiting antenna directionality. For example, the 1978
NASA Study of solar power satellites required a 1-km diameter transmitting antenna and a 10 km di-
ameter receiving rectenna for a microwave beam at 2.45 GHz. These sizes can be somewhat decreased
by using shorter wavelengths, although short wavelengths may have difficulties with atmospheric ab-
sorption and beam blockage by rain or water droplets. Because of the "thinned array curse," it is not
possible to make a narrower beam by combining the beams of several smaller satellites.
For earthbound applications, a large-area 10 km diameter receiving array allows large total power
levels to be used while operating at the low power density suggested for human electromagnetic
exposure safety. A human safe power density of 1 mW/cm2 distributed across a 10 km diameter
area corresponds to 750 megawatts total power level. This is the power level found in many modern
electric power plants.
Following World War II, which saw the development of high-power microwave emitters known
as cavity magnetrons, the idea of using microwaves to transmit power was researched. By 1964, a
miniature helicopter propelled by microwave power had been demonstrated.
Japanese researcher Hidetsugu Yagi also investigated wireless energy transmission using a di-
rectional array antenna that he designed. In February 1926, Yagi and his colleague Shintaro Uda
published their first paper on the tuned high-gain directional array now known as the Yagi antenna.
While it did not prove to be particularly useful for power transmission, this beam antenna has been
widely adopted throughout the broadcasting and wireless telecommunications industries due to its
excellent performance characteristics.
Wireless high power transmission using microwaves is well proven. Experiments in the tens of
kilowatts have been performed at Goldstone in California in 1975 and more recently (1997) at Grand
Bassin on Reunion Island. These methods achieve distances on the order of a kilometer.
Under experimental conditions, microwave conversion efficiency was measured to be around 54
A change to 24 GHz has been suggested as microwave emitters similar to LEDs have been made
with very high quantum efficiencies using negative resistance, i.e., Gunn or IMPATT diodes, and this
would be viable for short range links.
Recently, researchers at the University of Washington introduced power over Wi-Fi, which trickle-
charges batteries and powered battery-free cameras and temperature sensors using transmissions from
Wi-Fi routers.
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Chapter 4
COMPONENTS OF POWER
TRANSMISSION SYSTEM
There are three important components of this system are Microwave generator, Transmitting antenna,
and the receiving antenna.
4.1 MICROWAVE GENERATOR
Microwave generators are integrated solutions designed to generate and transmit microwave power.
Microwave generators are typically available in two configurations: Integrated Microwave Generators
or Modular Microwave Systems An integrated microwave generator is supplied in a single cabinet,
which contains of all generator systems and subcomponents. A modular microwave generator system
is supplied as separate components including but not limited to a power supply, magnetron head, and
cable assembly. Both systems require the same basic installation procedure: connecting the external
waveguide, electrical mains, cooling water lines and fieldbus interface.
4.2 TRANSMITTING ANTENNA
Transmitting antenna are use to transfer the signal from free space to the device. There are many kind
of slotted wave guide antenna available. Like parabolic dish antenna, microstrip patch an-tennas are
the popular type of transmitting antenna. Antennas are required by any radio receiver or transmit-
ter to couple its electrical connection to the electromagnetic field. Radio waves are electromagnetic
waves which carry signals through the air (or through space) at the speed of light with almost no
transmission loss. Radio transmitters and receivers are used to convey signals (information) in sys-
tems including broadcast (audio) radio, television, mobile telephones, Wi-Fi (WLAN) data networks,
trunk lines and point-to-point communications links (telephone, data networks), satellite links, many
remote controlled devices such as garage door openers, and wireless remote sensors, among many
others. Radio waves are also used directly for measurements in technologies including radar, GPS,
and radio astronomy. In each and every case, the transmitters and receivers involved require anten-
nas, although these are sometimes hidden (such as the antenna inside an AM radio or inside a laptop
computer equipped with Wi-Fi).
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4.3 RECTENNA
Its elements are usually arranged in rectenna. The current included by the microwaves in the rectenna
is rectied by the diode which powers a load connected across the diode. Scotty diodes are used be-
cause they have low voltage drop and high speed so that they have low power loss. rectenna are highly
efcient at converting microwave energy above 90 pecentage have been observed with regularity. The
basic addition to the mobile phone is going to be the rectenna. A rectenna is a rectifying antenna,
a special type of antenna that is used to directly convert microwave energy into DC electricity. Its
elements are usually arranged in a mesh pattern, giving it a distinct appearance from most antennae.
A simple rectenna can be constructed from a Schottky diode placed between antenna dipoles. The
diode recties the current induced in the antenna by the microwaves.
Figure 4.1: Block Diagram of a Rectenna
It has been theorized that similar devices, scaled down to the proportions used in nanotechnology,
could be used to convert light into electricity at much greater efciencies than what is currently possible
with solar cells. This type of device is called an optical rectenna. Theoretically, high efciencies can
be maintained as the device shrinks, but experiments funded by the United States National Renewable
energy Laboratory have so far only obtained roughly 1 percentage efciency while using infrared light.
Another important part of our receiver circuitry is a simple sensor.
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Chapter 5
WIRELESS POWER TRANSMISSION
Figure 5.1: Block diagram of Wireless power transmission for Mobile phones
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Chapter 6
SYSTEM DESIGN
The system designing of wireless charging of mobile phone using microwaves mainly consist of four
parts as transmitter design, receiver design, the Process of Rectication, sensor Circuitry.
6.1 TRANSMITTER SECTION
A transmitter is an electronic device which, when connected to an antenna, produces an electromag-
netic signal such as in radio and television broadcasting, two way communications or radar. Heating
devices, such as a microwave oven, although of similar design, are not usually called transmitters, in
that they use the electromagnetic energy locally rather than transmitting it to another location.
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6.1.1 The Magnetron
Magnetron is the combination of a simple diode vacuum tube with built in cavity resonators and an
extremely powerful permanent magnet. The typical magnet consists of a circular anode into which
has been machined with an even number of resonant cavities. The diameter of each cavity is equal to
a one-half wavelength at the desired operating frequency. The anode is usually made of copper and is
connected to a high-voltage positive direct current. In the center of the anode, called the interaction
chamber, is a circular cathode.
The magnetic fields of the moving electrons interact with the strong field supplied by the magnet. The
result is that the path for the electron flow from the cathode is not directly to the anode, but instead is
curved. By properly adjusting the anode voltage and the strength of the magnetic field, the electrons
can be made to bend that they rarely reach the anode and cause current flow. The path becomes
circular loops. Eventually, the electrons do reach the anode and cause current flow. By adjusting the
dc anode voltage and the strength of the magnetic field, the electron path is made circular. In making
their circular passes in the interaction chamber, electrons excite the resonant cavities into oscillation.
A magnetron, therefore, is an oscillator, not an amplifier. A takeoff loop in one cavity provides the
output
Magnetrons are capable if developing extremely high levels of microwave power.. When operated in
a pulse mode, magnetron can generate several megawatts of power in the microwave region. Pulsed
magnetrons are commonly used in radar systems. Continuous-wave magnetrons are also used and can
generate hundreds and even thousands of watts of power.
Figure 6.1: Magnetron
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6.1.2 Slotted wave guide antenna
A slotted waveguide is a waveguide that is used as an antenna in microwave radar applications. Prior
to its use in surface search radar, such systems used a parabolic segment reflector. For comparison, in
the parabolic type of antenna a feedhorn at the end of a waveguide directs a conical beam of output
energy toward the reflector, whence it is focused into a narrow collimated beam. Reflected energy
from the environment follows the reverse path and is focused by the reflector onto the feed horn
where it travels back to the receiver. The reflector must be built to a precision determined by the
wavelength used. For a one centimeter wavelength, a reflector precision of one or two millimeters
would be adequate.
A slotted waveguide has no reflector but emits directly through the slots. The spacing of the slots is
critical and is a multiple of the wavelength used for transmission and reception. The effect of this
geometry is to form a high gain antenna that is highly directional in the plane of the antenna. Without
augmentation a slotted waveguide is not as efficient as a parabolic reflector, lacking an ability to
focus in the vertical plane, but is much more durable and is less expensive to construct. The antenna’s
vertical focus is usually enhanced by the application of a microwave lens attached to the front of the
antenna. As this, like the companion slotted waveguide, is a one-dimensional device, it too may be
made relatively cheaply as compared to a parabolic reflector and feedhorn.
Usually a slotted waveguide antenna is protected by microwave transparent material, which may
visually obscure the slots. Nevertheless, it is easily distinguished from a parabolic reflector by its flat
or tube shape. The wave guide contains slits with size of about 1/4 wavelength, in a distance of 1/2
wavelength. In a related application, so-called leaky waveguides are also used in the determination of
railcar positions in certain rapid transit applications. They are used primarily to determine the precise
position of the train when it is being brought to a halt at a station, so that the doorway positions will
align correctly with queuing points on the platform or with a second set of safety doors should such
be provided.
Figure 6.2: Slotted Waveguide Antenna
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6.2 RECIEVER SECTION
The basic addition to the mobile phone is going to be the rectenna. A rectenna is a rectifying antenna,
a special type of antenna that is used to directly convert microwave energy into DC electricity. Its el-
ements are usually arranged in a mesh pattern, giving it a distinct appearance from most antennae. A
simple rectenna can be constructed from a Schottky diode placed between antenna dipoles. The diode
rectifies the current induced in the antenna by the microwaves. Rectenna are highly efficient at con-
verting microwave energy to electricity. Some experimentation has been done with inverse rectenna,
converting electricity into microwave energy, but efficiencies are much lower–only in the area of 1
percentage. With the advent of nanotechnology and MEMS the size of these devices can be brought
down to molecular level. It has been theorized that similar devices, scaled down to the proportions
used in nanotechnology, could be used to convert light into electricity at much greater efficiencies
than what is currently possible with solar cells. This type of device is called an optical rectenna. The-
oretically, high efficiencies can be maintained as the device shrinks, but experiments funded by the
United States National Renewable energy Laboratory have so far only obtained roughly 1 percentage
efficiency while using infrared light. Another important part of our receiver circuitry is a simple sen-
sor. This is simply used to identify when the mobile phone user is talking. As our main objective is to
charge the mobile phone with the transmitted microwave after rectifying it by the rectenna, the sensor
plays an important role. The whole setup looks something like this.
6.2.1 sensor circuit
The sensor circuitry is a simple circuit, which detects if the mobile phone receives any message signal.
This is required, as the phone has to be charged as long as the user is talking. Thus a simple F to V
converter would serve our purpose. In India the operating frequency of the mobile phone operators is
generally 900MHz or 1800MHz for the GSM system for mobile communication. Thus the usage of
simple F to V converters would act as switches to trigger the rectenna circuit to on.
A simple yet powerful F to V converter is LM2907. Using LM2907 would greatly serve our purpose.
It acts as a switch for triggering the rectenna circuitry. The general block diagram for the LM2907 is
given below.
Figure 6.3: Zener regulated frequency to voltage converter
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6.2.2 Rectenna
A rectifying antenna rectifies received microwaves into DC current. A rectenna comprises of a mesh
of dipoles and diodes for absorbing microwave energy from a transmitter and converting it into elec-
tric power. A simple rectenna can be constructed from a Schottky diode placed between antenna
dipoles as shown in Fig.3.4. The diode rectifies the current induced in the antenna by the microwaves.
Rectenna are highly efficient at converting microwave energy to electricity. In laboratory environ-
ments, efficiencies above 90 percentage have been observed with regularity. In future rectennas will
be used to generate large-scale power from microwave beams delivered from orbiting GPS satellites.
Figure 6.4: Rectenna
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6.2.3 Process of Rectification
Studies on various microwave power rectifier configurations show that a bridge configuration is better
than a single diode one. But the dimensions and the cost of that kind of solution do not meet our
objective. This study consists in designing and simulating a single diode power rectifier in “hybrid
technology” with improved sensitivity at low power levels. We achieved good matching between
simulation results and measurements thanks to the optimization of the packaging of the Schottky
diode. Microwave energy transmitted from space to earth apparently has the potential to provide
environmentally clean electric power on a very large scale. The key to improve transmission efficiency
is the rectifying circuit. The aim of this study is to make a low cost power rectifier for low and high
power levels at a frequency of 2.45GHz with good efficiency of rectifying operation. The objective
also is to increase the detection sensitivity at low power levels of power. Different configurations can
be used to convert the electromagnetic waves into DC signal. The study done showed that the use of
a bridge is better than a single diode, but the purpose of this study is to achieve a low cost microwave
rectifier with single Schottky diode for low and high power levels that has a good performance. This
study is divided on two kinds of technologies. The first is the hybrid technology and the second is
the monolithic one. The goal of this investigation is the development of a hybrid microwave rectifier
with single Schottky diode. The first study of this circuit is based on the optimization of the rectifier
in order to have a good matching of the input impedance at the desired frequency 2.45 GHz. Besides
the aim of the second study is the increasing of the detection sensitivity at low levels of power. The
efficiency of Schottky diode microwave rectifying circuit is found to be greater than 90
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WIRELESS CHARGING OF MOBILE PHONE USING MICROWAVES
6.2.4 Schottky Barrier Diode
Schottky barrier diode is different from a common P/N silicon diode. The common diode is formed
by connecting a P type semiconductor with an N type semiconductor, this is connecting between a
semiconductor and another semiconductor; however, a Schottky barrierdiode is formed by connecting
a metal with a semiconductor. When the metal contacts the semiconductor, there will be a layer of po-
tential barrier (Schottky barrier) formed on the contact surface of them, which shows a characteristic
of rectification. The material of the semiconductor usually is a semiconductor of n-type (occasionally
p-type), and the material of metal generally is chosen from different metals such as molybdenum,
chromium, platinum and tungsten. Sputtering technique connects the metal and the semiconductor.
A Schottky barrier diode is a majority carrier device, while a common diode is a minority carrier de-
vice. When a common PN diode is turned from electric connecting to circuit breakage, the redundant
minority carrier on the contact surface should be removed to result in time delay. The Schottky barrier
diode itself has no minority carrier, it can quickly turn from electric connecting to circuit breakage,
its speed is much faster than a common P/N diode, so its reverse recovery time Tr is very short and
shorter than 10 ns. And the forward voltage bias of the Schottky barrier diode is under 0.6V or so,
lower than that (about 1.1V) of the common PN diode. So, The Schottky barrier diode is a compar-
atively ideal diode, such as for a 1 ampere limited current PN interface.Below is the comparison of
power consumption between a common diode and a Schottky barrier diode:
P=0.6*1=0.6W
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Chapter 7
INDUCTIVE CHARGING
Though some Handsets on the market currently provide wireless charging, the technology is not ex-
actly same as mentioned here. For charging, phones are required to keep near the Charging Plate. It
uses inductively coupled Power Transfer System.
Figure 7.1: Existing Power Transfer system
A transmitter coil is positioned at the bottom (L1) and the receiver coil (L2) is situated at the top and
these coils are embedded into different electrical devices. L1 would be the Nokia Wireless Charging
Plate and L2 would be the Nokia Lumia 920, for example. In coming days, Microwave might fix
various issues in the current system.
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Chapter 8
ADVANTAGE
1) Charging of mobile phone is done wirelessly
2) We can saving time for charging mobiles
3) Wastage of power is less
4) Better than witricity as the distance the witricity can cover is about 20 meters whereas in this
technology we are using base station for transmission that can cover more area
5) Mobile get charged as we make call even during long journey
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Chapter 9
DISADVANTAGES
1) Radiation problems may occur
2)Network traffic may cause problems in charging
3)Charging depends on network coverage
4)Rate of charging may be of minute range
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Chapter 10
CONCLUSION
Thus this paper successfully demonstrates a novel method of using the power of microwave to charge
mobile phones without use of wired chargers. It provides great advantage to mobile phone users to
carry their phones anywhere even if the place is devoid of facilities for charging. It has effect on
human beings similar to that from cell phones at present. The use of rectenna and sensor in mobile
phone could provide new dimension in the revolution of mobile power.
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Chapter 11
REFERENCE
1.Theodore.S.Rappaport , “Wireless Communications Principles and Practice” .
2.www.seminarprojects.com
3.www.seminarsonly.com
4.www.wikipedia.org
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