WIRELESS CHARGING OF MOBILE PHONES USING

MICROWAVES

SARATH.S.KUMAR

BY

INTRODUCTIONCharging of mobile phones are becoming a problem

while travelling

This new technology of wireless charging will be a great relief for this

Here mobile phones can be charged from any where ,any time

We can charge our mobile phones by just making a call

Charging is done by converting the microwaves reaching the mobile phones to dc

MICROWAVESMicrowaves are emitted from objects such as cars and

planes, and from the atmosphere.

These microwaves can be detected to give information, such as the temperature of the object that emitted the microwaves.

Shorter microwaves are used in remote sensing.. Microwaves, used for radar, are just a few inches

long. Because microwaves can penetrate haze, light rain and snow, clouds and smoke.

Micro wave spectrum containing different band such as L band, S band etc

Here we have selected the license free 2.45 GHz ISM band for our purpose

The Industrial, Scientific and Medical (ISM) radio bands were originally reserved internationally for non-commercial use of RF electromagnetic fields for industrial, scientific and medical purposes

SCHEMATIC DIAGRAM

TRANSMITTER DESIGN

• A magnetron is a main part of transmitter

magnetron

Magnetron

The MAGNETRON is a self-contained microwave oscillator.

There's a heated cathode (coloured yellow)

A ring-shaped anode surrounds the cathode (colored red).

When the electrons try to zip from cathode to anode, , they feel a force and follow a curved path (blue circle)

As the electrons nip past the cavities, the cavities resonate and emit microwave radiation

MAGNETRON OPERATION PHASE 1Cathode centre at high negative volts

Anode at zero volts

No magnetic field

Electrons move in straight line

Magnet added

North pole on top

South pole at bottom

Electrons curve to the right

Electrons curve more when the magnetic field is increased

MAGNETRON OPERATION PHASE 1

Green path Weak magnet. All cathode electrons reach anode

Red path Magnetic field increased to “critical” value. Anode current decreases to a small value.

yellow path Magnetic field increased further. Anode current drops to zero

Magnetic field adjusted to where electrons just fail to reach the anode, the magnetron can oscillate

MAGNETRON OPERATION PHASE 2

Interaction space between cathode and cavities

2 electric fields, ac & dc in interaction space

Polarity is one instant of ac (µ-wave) field

The dc field extends radially from cavities to cathode

Electrons near cavities move tangentially to cavities

Electrons approaching the positive sides are speeded up

Electrons departing the positive side and approaching the negative side are slowed down.

MAGNETRON OPERATION PHASE 3

12 cavity magnetron

Rotating 6 spoke space charge

Space charge gives µ-wave energy to the cavity keeping it oscillating

8 cavity magnetron

4 spoke wheel

MAGNETRON OPERATION PHASE 4

Assume dc field & rf fields on cavities (magnetron oscillating

Electron approaching cavity gives up energy to cavity

Electron slows down accordingly

Then electron speeds up gaining energy from dc field

Electron eventually reaches cavity (anode current)

RECIEVER DESIGNThe reciever consists ofA RECTIFYING PART 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.

With the advent NANOTECHNOLOGY and MEMS the size of these devices can be brought down to molecular level.

SENSOR PART Another important part of our receiver circuitry is

a simple sensor. This is simply used to identify when the mobile phone user is talking.

Process of rectificationAN 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 electric power

Rectenna are highly efficient at converting microwave energy to electricity. In laboratory environments, efficiencies above 90% have been observed with regularity

.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.

RECTIFYING ANTENNA CIRCUITARY

Sensor circuitryDetects 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.

A simple F to V converter would serve our purpose.

Thus the usage of simple F to V converters (LM2907.)would act as switches to trigger the rectenna circuit to on.

It acts as a switch for triggering the rectenna circuitry.

Thus on the reception of the signal the sensor circuitry directs the rectenna circuit to ON and the mobile phone begins to charge using the microwave power.

ADVANTAGESHas wide application..Can charge our mobile phones any where any

time even if the place is devoid of facilities for charging.

Wired chargers can be eliminated…Have a wide future scope…Could provide a new dimension in the

revelation of mobile phone.

CONCLUSION It have great advantage of mobile phone

users they cannot carry their chargersRectenna and sensors gives new dimension in

mobile phone Initial cost large

BATTERY FULL

QUESTIONS