Wireless mobile charging using microwaves

WIRELESS MOBILE CHARGING USING MICROWAVES

Presented By :- Devyani B. Vaidya

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.

INTRODUCTION

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 following classes:

1. Gamma radiation ,

2. X-ray radiation ,

3. Ultraviolet radiation ,

4. Visible radiation ,

5. Infrared radiation ,

6. Microwave radiation and

7. Radio waves .

Fig.1.1. Electromagnetic Spectrum

Microwave Region

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 electromagnetic spectrum

Table 1.1 Microwave spectrum

2. TRANSMITTER SECTION

The transmitter section consists of two parts. They are:

Magnetron

Slotted waveguide antenna

2.1 Magnetron

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 cathode.

A magnetron, therefore, is an oscillator, not an amplifier. A takeoff loop in one cavity provides the output

Fig.2.1 Magnetron

Fig 2.2 Slotted waveguide antenna

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

4. ADVANTAGES

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.

5. DISADVANTAGES

Radiation problems may occur.

Network traffic may cause problems in charging.

Charging depends on network coverage.

Rate of charging may be of minute range.

6. APPLICATIONS

As the topics name itself this technology is used for “Wireless charging of mobile phones”.

Fig.6.1.Mobile getting charged from mobile tower

7. CONCLUSION

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 mobile power.

THANK YOU