Wireless Charging of rfregMobile

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Wireless Charging of Mobile

Phones Using Microwaves

Ram Charan M C

1DA06EC074DR AIT

SeminarPresented by:


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Contents OVERVIEW

INTRODUCTION

MICROWAVES TRANSMITER DESIGN

RECEIVER DESIGN

WORKING PRINCIPLE

SENSOR CIRCUITRY

CONCLUSION

BIBLIOGRAPHY


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OVERVIEW

In this paper a new proposal has beenmade so as to make automatic rechargingof the mobile phones possible 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 messagesignal using slotted wave guide antenna ata frequency is 2.45 GHz.


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There are minimal addition of a sensor, arectenna, and a filter to the mobile

handset.

The need for separate chargers for mobilephones is eliminated and makes charging

universal.

Thus the more you talk, the more is yourmobile phone charged


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INTRODUCTIONTHE ELECTROMAGNETIC SPECTRUM

The electromagnet ic spectrumis the range of allpossible frequencies of electromagnetic radiation.

when white light is shone through a prism it is

separated out into all the colors of the rainbow; this isthe visible spectrum.

It is easy to explain some of the properties of light bypretending that it is made of tiny particles called

photons And it is easy to explain other properties of light bypretending that it is some kind of wave.


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The Radio Window


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MICROWAVES

Microwaves are electromagnetic wave with wavelengths ranging fromas long as one meter to as short as one millimeter, or equivalently, withfrequencies between 300 MHz (0.3 GHz) and 300 GHz

Shorter microwaves are used in remote sensing. These microwaves areused for radar like the Doppler radar used in weather forecasts.Microwaves, used for radar are just a few inches long

Microwave waves are used in the communication industry and in thekitchen as away to cook foods.

Microwave radiation is still associated with energy levels that are usuallyconsidered harmless


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The ISM bands are defined

by the ITU-T in S5.138 and

S5.150 of the Radio

regulations. Here we have selected the

license free 2.45 GHz ISM

band for our purpose.

IEEE 802.11b wirelessEthernet also operates on

the 2.45 GHz band


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Radio and microwave powertransmission Power transmission via radio waves can

be made more directional, allowing longer

distance power beaming . A rectenna may be used to convert the

microwave energy back into electricity.

A human safe power density of 1 mW/cm

2

can be generated and distributed across a10 km diameter area corresponds to 750megawatts total power level.
http://en.wikipedia.org/wiki/Rectennahttp://en.wikipedia.org/wiki/Rectenna


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BRIEF HISTORY OF MICROWAVE

POWER TRANSMISSION


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MOBILE PHONE


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TRANSMITTING BASE

STATION

A base transceiverstation (BTS) orcell siteis a piece of equipmentthat facilitates wireless

communication betweenuser equipment (UE) anda network. UEs aredevices like mobilephones (handsets), WLL

phones, computers withwirelessinternetconnectivity, WiFi andWiMAX gadgets etc
http://en.wikipedia.org/wiki/File:GSM_base_station_2.JPGhttp://en.wikipedia.org/wiki/File:GSM_base_station_2.JPGhttp://en.wikipedia.org/wiki/Wireless_internethttp://en.wikipedia.org/wiki/File:GSM_base_station_2.JPGhttp://en.wikipedia.org/wiki/File:BTS_Vodafone.jpghttp://en.wikipedia.org/wiki/Wireless_internet


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TRANSMITTER DESIGN

THE MAGNETRON

A microwave tube in whichelectrons generated from aheated cathode are affected bymagnetic and electric fields insuch a way as to producemicrowave radiation.

It is a self-containedmicrowave oscillator thatoperates differently from thelinear-beam tubes, such as theTWT and the klystron.

Magnetrons can produce

continuous power outputs ofmore than 1 kW at a frequencyof 1 GHz.


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Magnetron is classed asa diode because it hasno grid .

Cathode is indirectlyheated& electrons are,

generated from aheated cathode, moveunder the combinedforce of a radial electricfield and an axialmagnetic field.

This causes movingelectrons to interactsynchronously withtraveling-wavecomponents of amicrowave standing-wave pattern in such a

manner that electronpotential energy isconverted to microwaveenergy with highefficiency
http://www.radartutorial.eu/08.transmitters/pic/mag06.big.gif


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The open space between the plate and the cathode iscalled the INTERACTION SPACE. In this space theelectric and magnetic fields interact to exert force uponthe electrons.


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CROSSED-ELECTRON and MAGNETIC fields are usedin the magnetron to produce the high-power output

required in radar and communications equipment.

RECEIVER DESIGN


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RECEIVER DESIGN

A rectenna is a

rectifying antenna,converts microwaveenergy into DCelectricity.

A simple rectenna canbe constructed from aschottky diode placedbetween antenna

dipoles. The dioderectifies the currentinduced in theantenna by themicrowaves.
http://en.wikipedia.org/wiki/File:Dipolentstehung.gif


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Rectenna

An antennacomprising a mesh of

dipoles and diodes

for absorbing

microwave energyfrom a transmitter

and converting it into

electric power.

Microwaves are receivedwith about 85% efficiency

at 2.45GHz


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Rectennae have high efficiency convertingmicrowave energy to electricity above 90%.Withthe advent of nanotechnology and MEMS the sizeof these devices can be brought down tomolecular level called optical rectenna.

Wi l t i i f


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Wireless power transmission for

Mobile phones

As our main objective is to charge the mobile phone withthe transmitted microwave after rectifying it by the rectenna,

the sensor plays an important role.


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WORKING PRINCIPLE : - THE

PROCESS OF RECTIFICATION

The key to improve transmission efficiency

is the rectifying circuit. The aim of this

study is to make a low cost and efficientpower rectifier for low and high power

levels at frequency of 2.45 GHz with good

efficiency of rectifying operation.


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This circuit is based on the optimization of the rectifier inorder to have a good matching of the input impedance atdesired frequency 2.45GHz and detection sensitivity at lowlevels of power. Optimization of circuit done by introducing the parasiticelements of the Schottky diode which were optimized toreach a good impedance matching and an importantconversion efficiency at desired frequency 2.45 GHz .


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SENSOR CIRCUITRY

The sensor circuitry detects if the mobile

phone receives any message signal.

In India the operating frequency of the mobile

phone operators is generally 900MHz or1800MHz for the GSM system for mobile

communication. Thus the usage of simple F

to V such as LM2907 converters would act as

switches to trigger the rectenna circuit to on.


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Fig shows F to V converter LM2907.Using LM2907

would greatly serve our purpose. It acts as a switch for

triggering the rectenna circuitry. Thus on the receptionof the signal the sensor circuitry directs the rectenna

circuit to ON and the mobile phone begins to charge

using the microwave power.

Advantages Disadvantages


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Advantages

Charging of mobile phonebattery is independent of theirmanufacturer and battery

make. The recharging of the mobile

phones is done automaticallyas you talk in your mobilephone

The need for separate

chargers for mobile phones iseliminated and makescharging universal.

Microwave energy apparentlyhas the potential to provideenvironmentally clean electricpower for very large number ofusers.

The mobile phone users cancarry their phones anywhereeven if the place is devoid offacilities for charging

Disadvantages

Rectenna is quite bulky , Furtherreduction in size is required.

Power level density desired for

wireless power transmission mayexceed the Human safe level.

The Mobile phone Battery is notstandardized, hence design ofreceivers may vary.

The Magnetron at the Base

transceiver station dissipates toomuch Heat and this is to bedesigned for optimum efficiencyfor wireless power transmission.

At the Base transceiver stationthere is a requirement ofmaintenance of Magnetron whichhas to be provided with the heatsink.


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CONCLUSION

Thus this paper successfully demonstrates a

novel method of using the power of the

microwave to charge the mobile phones without

the use of wired chargers. Thus this methodprovides great advantage to the mobile phone

users to carry their phones anywhere even if the

place is devoid of facilities for charging. A novel

use of the rectenna and a sensor in a mobilephone could provide a new dimension in the

revelation of mobile phone.


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BIBLIOGRAPHY Tae- Whan yoo and Kai Chang, " Theoretical and

Experimental Development of 10 and 35 GHz rectennas"IEEE Transaction on microwave Theory and Techniques,vol. 40.NO.6.June.1992.

5 Hawkins, Joe, et al, "Wireless Space Power Experiment,"in Proceedings of the 9th summer Conference ofNASA/USRA Advanced Design Program and AdvancedSpace Design Program, June 14-18, 1993.

MW Medley Jr and MW Medley, 'Microwave and RFcircuits: analysis, synthesis, and design', Artech House,

Norwood, MA, 1993. Falcone, Vincent J., "Atmospheric Attenuation of Microwave

Power," Journal of microwave Power, 5(4), 1970.


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