In this paper, we deal with the topic of automatic
recharging of the mobile phones 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.
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.
Microwaves are electromagnetic wave 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.
Microwave radiation is still associated with energy levels that are usually
Power transmission via radio waves can be made
more directional, allowing longer distance power
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.
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
continuous power outputs of
more than 1 kW at a frequency of
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
components of a
microwave standingwave pattern.
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
CROSSED-ELECTRON and MAGNETIC fields are used in
the magnetron to produce the high-power output
required in radar and communications equipment.
rectenna is a
The diode rectifies the
current induced in the
“An antenna comprising a
mesh of dipoles and
diodes for absorbing
microwave energy from
a transmitter and
converting it into
Microwaves are received
with about 85% efficiency
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.
•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 is done by introducing the parasitic
elements of the Schottky.
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.
The sensor circuitry detects if the mobile
phone receives any message signal.
The usage of simple F to V such as LM2907
converters would act as switches to trigger the
rectenna circuit to on.
Fig shows F to V converter LM2907.It acts as a switch for
triggering the rectenna circuitry.
of mobile phone
battery is independent of the
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.
Microwave energy apparently
has the potential to provide
environmentally clean electric
The mobile phone users can
carry their phones anywhere
even if the place is devoid of
facilities for charging.
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
requirement of heat sink.
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.. A novel use of the rectenna and a
sensor in a mobile phone could provide a new
dimension in the revelation of mobile phone.
Tae- Whan yoo and Kai Chang, " Theoretical and
Experimental Development of 10 and 35 GHz rectennas" IEEE
Transaction on microwave Theory and Techniques, vol.
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,
Falcone, Vincent J., "Atmospheric Attenuation of Microwave
Power," Journal of microwave Power, 5(4), 1970.