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:
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
Here as we can see there are two part. One is transmitting part and the other is the
At the transmitting end there is one microwave power source which is actually
The microwave signal is transmitted along with message signal using slotted wave
At the receiver side sensor search for the mobile signal , in addition it has a
Rectenna receives the transmitted power and converts the microwave power to
The transmitter section consists of two parts. They are:
Slotted waveguide antenna
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
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
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.
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.
The use of wired chargers are eliminated.
The need of different types of chargers by different manufacturers is totally
The phone can be charged at any place and any time.
Only one microwave transmitter can serve to all the service providers in that
The more we talk the more the phone get charged
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
Process is of high cost
Charging depends on network coverage
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.