Wireless Charging of Mobile Phones Using Microwaves

By, HARISH N NAYAK

8th SEM ECE

CONTENTS• INTRODUCTION

• MICROWAVE REGION

• BLOCK DIAGRAM

• TRANSMITTER SECTION

• RECEIVER SECTION

• ADVANTAGES

• DISADVANTAGES

• APPLICATION

• CONCLUSION

INTRODUCTION Mobile phones becoming basic part of life

Recharging of mobile phones is a big problem

Objective—to recharge any mobile phone independent of manufacturer and battery make

Achieved by recharging battery while talking using microwaves

Additives to mobile handsets:SensorRectenna

MICROWAVE REGION Microwaves are the Radio wave which has the wave length range of 1 mm to 1 meter

and the frequency is 300MHz to 300GHz.

Microwaves are good for transmitting information from one place to another

It is because microwave energy can penetrate rain and snow, clouds, and smoke

The frequency selection is another important aspect in transmission. Here we are going

to use the S band of the Microwave Spectrum, which lies between 2-4GHz.We have selected the license free 2.45 GHz band for our purpose.

PRINCIPLE OF OPERATION

Transmitting station with the microwave transmitter

sensor

Rectenna

RF cable

circulator

waveguide

Slotted waveguideAntenna

mobile signal

OPERATION Here as we can see there are two part. One is transmitting part and the other is

the Receiving part At the transmitting end there is one microwave power source which is actually

producing microwavesThe microwave signal is transmitted along with message signal using slotted wave

guide antenna

At the receiver side sensor search for the mobile signal , in addition it has a “RECTENNA”.

Rectenna receives the transmitted power and converts the microwave power to DC power.

TRANSMITTER SECTION The transmitter section consists of two parts. They are:

Magnetron Slotted waveguide antenna

Magnetron

MAGNETRON

Magnetron is a high power microwave oscillator and it is used in microwave oven and radar transmitter.

Magnetron is the combination of a simple diode vacuum tube with built in cavity resonators and an extremely powerful permanent magnet.

Magnetron is capable to deliver more power than reflex klystron or gunn diode

Magnet is setup to affect the path of travel of electrons that are in transit from cathode to the anode plate.

THE SLOTTED WAVEGUIDE ANTENNA

The slotted waveguide antenna consists of 8 waveguide sections with 8 slots on each section. These 64 slots radiate the power uniformly through free space to the rectenna. The slotted waveguide antenna is ideal for power transmission because of its high efficiency (> 95%) and high power handling capability.

Slotted antenna arrays used with waveguides are popular antenna in navigation, radar and other high-frequency systems

Has high efficiency and gain of 13dB

Here we use frequency of 2.45GHz

RECEIVER SECTIONRECTENNA

The basic addition to the mobile phone is going to be the rectennas and sensor

Rectenna = Rectifier + Antenna.A rectifying antenna called a rectenna receives the transmitted power and converts the

microwave power to direct current (DC) power. Here antenna receives the microwave signal and diode rectifies the current induced in

the antenna by the microwave

This demonstration rectenna consists of 6 rows of dipoles antennas where 8 dipoles belong to each row. Each row is connected to a rectifying circuit which consists of low pass filters and a rectifier.

The rectifier is a GaAs Schottky barrier diode that is impedance matched to the dipoles by a low pass filter.

SENSOR CIRCUITRY

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.

ADVANTAGES

The use of wired chargers are eliminated.

The need of different types of chargers by different manufacturers is totally eliminated

The phone can be charged at any place and any time.

Only one microwave transmitter can serve to all the service providers in that area.

The more we talk the more the phone get charged

DISADVANTAGES

Wireless transmission of the energy causes some effects to human body, because

of its radiation

Network traffic may cause problems in charging

Practical possibilities are not yet applicable as there is no much advancement in

this field.

Process is of high cost

Charging depends on network coverage

CONCLUSION

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.