1. Wireless Charging of Mobile Phones Using Microwaves
Seminar
Presented by:
Ram Charan M C
1DA06EC074
DR AIT

2. Contents OVERVIEW INTRODUCTION MICROWAVES TRANSMITER DESIGN
RECEIVER DESIGN
WORKING PRINCIPLE
SENSOR CIRCUITRY
CONCLUSION
BIBLIOGRAPHY

3. OVERVIEW
In this paper a new proposal has been made so as to make automatic recharging of 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 message signal using slotted wave guide antenna at a frequency is 2.45 GHz.

4. There are minimal addition of a sensor, a “rectenna”, and a filter to the mobile handset.
The need for separate chargers for mobile phones is eliminated and makes charging universal.
Thus the more you talk, the more is your mobile phone charged

5. INTRODUCTION THE ELECTROMAGNETIC SPECTRUM
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation.
when white light is shone through a prism it is separated out into all the colors of the rainbow; this is the visible spectrum.
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.

7. The Radio Window

8. MICROWAVES
Microwaves are electromagnetic wave with wavelengths ranging from as long as one meter to as short as one millimeter, or equivalently, with frequencies between 300 MHz (0.3 GHz) and 300 GHz
Shorter microwaves are used in remote sensing. These microwaves are used 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 the kitchen as away to cook foods.
Microwave radiation is still associated with energy levels that are usually considered harmless

9. The ISM bands are defined by the ITU-T in S5. 138 and S5
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 b wireless Ethernet also operates on the 2.45 GHz band

10. Radio and microwave power transmission
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/cm2 can be generated and distributed across a 10 km diameter area corresponds to 750 megawatts total power level.

11. BRIEF HISTORY OF MICROWAVE POWER TRANSMISSION

12. MOBILE PHONE

13. TRANSMITTING BASE STATION
A base transceiver station (BTS) or cell site is a piece of equipment that facilitates wireless communication between user equipment (UE) and a network. UEs are devices like mobile phones (handsets), WLL phones, computers with wireless internet connectivity, WiFi and WiMAX gadgets etc

14. TRANSMITTER DESIGN THE MAGNETRON
A microwave tube in which electrons generated from a heated cathode are affected by magnetic and electric fields in such a way as to produce microwave radiation.
It is a self-contained microwave oscillator that operates differently from the linear-beam tubes, such as the TWT and the klystron.
Magnetrons can produce continuous power outputs of more than 1 kW at a frequency of 1 GHz.

15. Magnetron is classed as a diode because it has no grid .
Cathode is indirectly heated& electrons are, generated from a heated cathode, move under the combined force of a radial electric field and an axial magnetic field.
This causes moving electrons to interact synchronously with traveling-wave components of a microwave standing-wave pattern in such a manner that electron potential energy is converted to microwave energy with high efficiency

16. The open space between the plate and the cathode is called the INTERACTION SPACE. In this space the electric and magnetic fields interact to exert force upon the electrons.

17. CROSSED-ELECTRON and MAGNETIC fields are used in the magnetron to produce the high-power output
required in radar and communications equipment.

18. RECEIVER DESIGN
A rectenna is a rectifying antenna, converts microwave energy into DC electricity.
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.

19. Rectenna
“An antenna comprising a mesh of dipoles and diodes for absorbing microwave energy from a transmitter and converting it into electric power.”
Microwaves are received with about 85% efficiency at 2.45GHz

20. Rectennae have high efficiency converting microwave energy to electricity above 90%.With the advent of nanotechnology and MEMS the size of these devices can be brought down to molecular level called optical rectenna.

21. Wireless power transmission for Mobile phones
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.

22. 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 efficient power rectifier for low and high power levels at frequency of 2.45 GHz with good efficiency of rectifying operation.

23. This circuit is based on the optimization of the rectifier in order to have a good matching of the input impedance at desired frequency 2.45GHz and detection sensitivity at low levels of power.
Optimization of circuit done by introducing the parasitic elements of the Schottky diode which were optimized to reach a good impedance matching and an important conversion efficiency at desired frequency 2.45 GHz .

24. 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 or 1800MHz 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.

25. Fig shows F to V converter LM2907
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 reception of the signal the sensor circuitry directs the rectenna circuit to ON and the mobile phone begins to charge using the microwave power.

26. Advantages Disadvantages
Charging of mobile phone battery is independent of their manufacturer and battery make.
The recharging of the mobile phones is done automatically as you talk in your mobile phone
The need for separate chargers for mobile phones is eliminated and makes charging universal.
Microwave energy apparently has the potential to provide environmentally clean electric power for very large number of users.
The mobile phone users can carry their phones anywhere even if the place is devoid of facilities for charging
Disadvantages
Rectenna is quite bulky , Further reduction in size is required.
Power level density desired for wireless power transmission may exceed the Human safe level.
The Mobile phone Battery is not standardized, hence design of receivers may vary.
The Magnetron at the Base transceiver station dissipates too much Heat and this is to be designed for optimum efficiency for wireless power transmission.
At the Base transceiver station there is a requirement of maintenance of Magnetron which has to be provided with the heat sink.

27. 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 method provides 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 mobile phone could provide a new dimension in the revelation of mobile phone.

28. 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 of NASA/USRA Advanced Design Program and Advanced Space Design Program, June 14-18, 1993.
MW Medley Jr and MW Medley, 'Microwave and RF circuits: analysis, synthesis, and design', Artech House, Norwood, MA, 1993.
Falcone, Vincent J., "Atmospheric Attenuation of Microwave Power," Journal of microwave Power, 5(4), 1970.

29. THANK YOU