Wireless Charging of Mobile Phones Using Microwaves

INTRODUCTION Mobile phones being a basic part of life and the recharging of batteries is always a problem. This paper is new proposal 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. Microwave wavelengths range from approximately one millimeter to thirty centimeters

The Electromagnetic Spectrum Hz M Microwaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds, and smoke.

Shorter microwaves are used in remote sensing. These microwaves are used for radar like the Doppler radar used in weather forecasts Microwave radiation is still associated with energy levels that are usually considered harmless

Microwave frequency bands L Band S C X Ku K Ka Q U V 1 to 2 GHz 2 to 4 GHz 4 to 8 GHz 8 to 12 GHz 12 to 18 GHz 18 to 26 GHz 26 to 40 GHz 30 to 50 GHz 40 to 60 GHz 46 to 56 GHz W Band 56 to 100 GHz The frequency selection is another important aspect in transmission. Here we have selected the license free 2.45 GHz(Industrial, Scientific and Medical) ISM band for this purpose.

TRANSMITTER DESIGN The MAGNETRON is a self-contained microwave oscillator that operates differently from the linear-beam tubes, such as the TWT and the klystron. Magnetron is used to produce high-power output required in radar and communications equipment Magnetron inner parts

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

Entire System Design Description

Rectenna What is Rectenna ? Rectenna = Rectifier + Antenna. In our design it consists of a single diode power rectifier “in hybrid technology” with improved sensitivity at low power levels. Antennas can be of any shape such a way to maximize the microwave absorption in order to convert it back to electricity. A diode is soldered directly to the feed point at the center of the antenna. No matching section is used due to area constraints in cell phones.

Antenna Spirals are supposed to have a nearly frequency independent behavior between a certain lower and upper frequency 3D-view of 8x8 antennas Single spiral antenna Spiral antenna has diode at the center. Single Rectenna is approx 23 mm2 , these are arranged to form an array suitable to shape of mobile phone. These Rectennas are very thin as sheets and can be used to at the back of the Cell phones.

Design of simple Rectifier DC Output Across R Diode Input From Antenna Inductors for Filtering This is the circuit connected to the antennas in order to convert AC Microwave in to DC power for charging.

The above diagram typically depicts the Schottky diode microwave rectifying circuit. The efficiency of the above circuit is found to be greater than 90%.

SENSOR CIRCUITRY The sensor circuitry is a simple circuit, which detects the mobile phone service provider (eg : Airtel etc) signal. This a simple F to V converter, this would serve our purpose. 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 as long as the user talks over cell phone.

The general block diagram for the LM2907 is given below 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.

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. This has effect on human beings similar to that from cell phones at present.

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