1. What is a spectrum?
Ans: When white light is shone through a prism it is separated out into all the colors
of the rainbow, this is the visible spectrum. So white light is a mixture of all colors.
Black is not a color, it is what you get when all the light is taken away. Some
physicists pretend that light consists of tiny particles which they call photons. They
travel at the speed of light . The speed of light is about 300,000,000 m/s.
The visible spectrum is just one small part of the electromagnetic spectrum.
These electromagnetic waves are made up of to two parts. The first part is an electric
field and the second part is a magnetic field. So that is why they are called
electromagnetic waves. The two fields are at right angles to each other.
The "electromagnetic spectrum" of an object has a different meaning, and is
instead the characteristic distribution of electromagnetic radiation emitted or absorbed
by that particular object. The electromagnetic spectrum extends from below the low
frequencies used for modern radio communication to gamma radiation at the short-
wavelength (high-frequency) end, thereby covering wavelengths from thousands of
kilometres down to a fraction of the size of an atom.
Most parts of the electromagnetic spectrum are used in science for
spectroscopic and other probing interactions, as ways to study and characterize matter.
In addition, radiation from various parts of the spectrum has found many
other uses for communications and manufacturing
The types of electromagnetic radiation are broadly classified into the
1. Gamma radiation ,
2. X-ray radiation ,
3. Ultraviolet radiation ,
4. Visible radiation ,
5. Infrared radiation ,
6. Microwave radiation and
7. Radio waves .
Microwave wavelengths range from approximately one millimeter to thirty
centimeters (about twelve inches).
Microwaves have wavelengths that can be measured in centimeters! The
longer microwaves, those closer to a foot in length, are the waves which heat our food
in a microwave oven.
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 clouds and smoke, these waves are good for viewing the Earth from space
Microwave waves are used in the communication industry and in the kitchen
as a way to cook foods. Microwave radiation is still associated with energy levels that
are usually considered harmless except for people with pace makers.
Fig.1.2 Microwave region of
Table 1.1 Microwave spectrum
2. TRANSMITTER SECTION
The transmitter section consists of two parts. They are:
Slotted waveguide antenna
Magnetron is the combination of a simple diode vacuum tube with built in
cavity resonators and an extremely powerful permanent magnet.
The anode is usually made of copper and is connected to a high-voltage
positive direct current.
In the center of the anode, called the interaction chamber, is a circular
A magnetron, therefore, is an oscillator, not an amplifier. A takeoff loop in
one cavity provides the output
2.2 Slotted Waveguide Antenna
The slotted waveguide is used in an omni-directional role. It is the simplest
ways to get a real 10dB gain over 360 degrees of beam width. The Slotted waveguide
antenna is a Horizontally Polarized type Antenna, light in weight and weather proof.3
Tuning screws are placed for tweaking the SWR and can be used to adjust the
centre frequency downwards from 2320MHz nominal to about 2300 MHz .This antenna
is available for different frequencies.
This antenna, called a slotted waveguide, is a very low loss transmission line.
It allows propagating signals to a number of smaller antennas (slots). The signal is
coupled into the waveguide with a simple coaxial probe, and as it travels along the
guide, it traverses the slots.
Each of these slots allows a little of the energy to radiate. The slots are in a
linear array pattern. The waveguide antenna transmits almost all of its energy at the
horizon, usually exactly where we want it to go. Its exceptional directivity in the
elevation plane gives it quite high power gain. Additionally, unlike vertical collinear
antennas, the slotted waveguide transmits its energy using horizontal polarization, the
best type for distance transmission.
3. RECEIVER SECTION
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.
Its elements are usually arranged in a mesh pattern, giving it a distinct
appearance from most antennae. 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. Rectenna are highly efficient at converting microwave
energy to electricity.
Fig 3.1.Block Diagram
3.1 Sensor Circuit
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.
Fig. 3.2 Block diagram for the LM2907 Fig. 3.3 LM2907 IC
3.2 Process of Rectification
Studies on various microwave power rectifier configurations show that a
bridge configuration is better than a single diode one. But the dimensions and the cost
of that kind of solution do not meet our objective. This study consists in designing and
simulating a single diode power rectifier in “hybrid technology” with improved
sensitivity at low power levels. We achieved good matching between simulation results
and measurements thanks to the optimization of the packaging of the Schottky diode.
This study is divided on two kinds of technologies. The first is the hybrid
technology and the second is the monolithic one.
Fig 3.4 Rectification Fig 3.5 Rectenna Array
Charging of mobile phone is done wirelessly.
We can saving time for charging mobiles.
Wastage of power is less.
Better than witricity as the distance the witricity can cover is
about 20 meters whereas in this technology we are using base
station for transmission that can cover more area.
Mobile get charged as we make call even during long journey.
Radiation problems may occur.
Network traffic may cause problems in charging.
Charging depends on network coverage.
Rate of charging may be of minute range.
As the topics name itself this technology is used for “Wireless
charging of mobile phones”.
Fig.6.1.Mobile getting charged from mobile tower
Thus this paper successfully demonstrates a novel method
of using the power of microwave to charge mobile phones without
use of wired chargers. It provides great advantage to mobile phone
users to carry their phones anywhere even if the place is devoid of
facilities for charging. It has effect on human beings similar to that
from cell phones at present. The use of Rectenna and sensor in
mobile phone could provide new dimension in the revolution of
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