wireless mobile charger report.pdf

WIRELESS CHARGING OF MOBILE USING MICROWAVE

CHAPTER 1

INTRODUCTION The principle of wireless charging has been around for over a century but only now are we beginning to recognize its true potential. First, we need to be careful about how liberal we use "wireless" as a term; such a word implies that you can just walk around the house or office and be greeted by waves of energy beamed straight to your phone. We're referring, largely, to inductive charging the ability to manipulate an electromagnetic field in order to transfer energy a very short distance between two objects (a transmitter and receiver). It's limited to distances of just a few millimeters for the moment, but even with this limitation, such a concept will allow us to power up phones, laptops, keyboards, kitchen appliances, and power tools from a large number number of places: in our homes, homes, our cars, and even the mall. There are three types of wireless charging. 1. Inductive charging 2. Radio charging 3. Resonance charging

1.1 INDUCTIVE CHARGING Inductive charging charges electrical batteries using electromagnetic induction. A charging station sends energy through inductive coupling to an electrical device, which stores the energy in the batteries. Because there is a small gap between the two coils, inductive charging is one kind of short distance wireless energy transfer. Inductive charging is used for charging mid-sized items such as cell phones, MP3 players and PDAs. In inductive charging, an adapter equipped with contact points is attached to the device's back plate. When the device requires a charge, it is placed on a conductive charging pad, which is plugged into a socket.

Dept. of ECE SDMIT Ujire

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1.2 RADIO CHARGING Radio charging is only effective for small devices. The battery of a laptop computer, for example, requires more power than radio waves can deliver. The range also limits the effectiveness of radio charging, which works on the same principle as an AM/FM radio does: The closer the receiver is to the transmitter, the better reception will be. In the case of wireless radio charging, better reception translates to a stronger charge for the item.

1.3 RESONANCE CHARGING Resonance charging is used for items that require large amounts of power, of power, such as an electric car, robot, vacuum cleaner or laptop computer. In resonance charging, a copper coil attached to a power source is the sending unit. Another coil, attached to the device to be charged, is the receiver. Both coils are tuned to the same electromagnetic frequency, which makes it possible it possible for energy to be transferred from one to the other. A new method is developed in order to charge mobile phones, by using microwaves.


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CHAPTER 2

ELECTROMAGNETIC ELECTROMAGNETIC SPECTRUM

Fig.2.1 electromagnetic spectrum The electromagnetic spectrum[4] is the range of all possible frequencies of electromagnetic radiation. The electromagnetic spectrum extends from below the low frequencies used for modern radio communication to gamma radiation at the shortwavelength (high-frequency) end. Electromagnetic radiation is the means for many of our interactions with the world: light allows us to see; radio waves give us TV and radio; microwaves are used in radar communications; X-rays allow glimpses of our internal organs; and gamma rays let us eavesdrop on exploding stars thousands of light-years away. Electromagnetic radiation is the messenger, or the signal from sender to receiver. The sender could be a TV station, a star, or the burner on a stove. The receiver could be a TV set, an eye, or an X-ray film. In each case, the sender gives off or reflects some kind of electromagnetic radiation. All these different kinds of electromagnetic radiation actually differ only in a single property — property — their their wavelength. When electromagnetic radiation is spread out according to


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WIRELESS CHARGING OF MOBILE USING MICROWAVE its wavelength, the result is a spectrum, as seen in Fig. The visible spectrum, as seen in a rainbow, is only a small part of the whole electromagnetic spectrum . The electromagnetic spectrum is divided into following classes, 1. Gamma radiation 2. X-ray radiation 3. Ultraviolet radiation 4. Visible radiation 5. Infrared radiation 6. Microwave radiation 7. Radio waves

2.1 MICROWAVE REGION Microwaves[5] are the Radio wave which has the wave length range of 1 mm to 1 meter and the frequency is 300MHz to 300GHz. Each and every object on the earth absorb different amount of microwave energy. Microwaves are good for transmitting information from one place to another because microwave energy can penetrate haze, light rain and snow, clouds, 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. 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 ISM band for our purpose. The Industrial, Scientific and Medical (ISM) radio bands were originally reserved internationally for non-commercial use of RF electromagnetic fields for industrial, scientific and medical purposes.

In recent years they have also been used for license-free error-tolerant

communications applications such as wireless LANs and Bluetooth. According to the range of frequencies there are different frequency bands are present. Specialized vacuum tubes are used to generate microwaves. These devices Dept. of ECE SDMIT Ujire

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WIRELESS CHARGING OF MOBILE USING MICROWAVE operate on different principles from low-frequency vacuum tubes, using the ballistic motion of electrons in a vacuum under the influence of controlling electric or magnetic fields, and include the magnetron (used in microwave ovens), klystron, traveling-wave tube (TWT), and gyrotron. These devices work in the density modulated mode, rather than the current modulated mode. This means that they work on the basis of clumps of electrons flying ballistically through them, rather than using a continuous stream of electrons. Cutaway view inside a cavity magnetron as used i n a microwave oven. Low-power microwave sources use solid-state devices such as the field-effect transistor (at least at lower frequencies), tunnel diodes, Gunn diodes, and IMPATT diodes. Low-power sources are available as benchtop instruments, rackmount instruments, and embeddable modules and in card-level formats. A maser is a solid state device which amplifies microwaves using similar principles to the laser, which amplifies higher frequency light waves. All warm objects emit low level microwave black body radiation, depending on their temperature, so in meteorology and remote sensing microwave radiometers are used to measure the temperature of objects or terrain. The sun and other astronomical radio sources such as Cassiopeia, emit low level microwave radiation which carries information about their makeup, which is studied by radio astronomers using receivers called radio telescopes. The cosmic microwave background radiation (CMBR), for example, is a weak microwave noise filling empty space which is a major source of information on cosmology's Big Bang theory of the origin of the Universe.


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CHAPTER 3

GENERAL BLOCK DIAGRAM

Fig 3.1 Block diagram

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 microwaves. Which is attach to the Coax-Waveguide and here Tuner is the one which match the impedance of the transmitting antenna and the microwave source. Directional Coupler helps the signal to propagate in a particular direction. It spread the Microwaves in a space and sent it to the receiver side. Receiver side Impedance matching circuit receives the microwave signal through Rectena circuit. This circuit is nothing but the combination of filter circuit and the schottky Diode. Which actually convert our microwave in to the DC power!


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CHAPTER 4

TRANSMITTER SECTION The transmitter section consists of two parts. They are: 1. Magnetron

2. Slotted waveguide antenna

4.1 MAGNETRON

Fig.4.1 Magnetron Magnetron[4] is the combination of a simple diode vacuum tube with built in cavity resonators and an extremely powerful permanent magnet. The typical magnet consists of a circular anode into which has been machined with an even number of resonant cavities. The diameter of each cavity is equal to a one-half wavelength at the desired operating frequency. 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. The magnetic fields of the moving electrons interact with the strong field supplied by the magnet. The result is that the path for the electron flow from the cathode is not directly to the anode, but instead is curved. By properly adjusting the anode voltage and the strength of the magnetic field, the electrons can be made to bend Dept. of ECE SDMIT Ujire

that they rarely Page 7

WIRELESS CHARGING OF MOBILE USING MICROWAVE reach the anode and cause current flow. The path becomes circular loops. Eventually, the electrons do reach the anode and cause current flow. By adjusting the dc anode voltage and the strength of the magnetic field, the electron path is made circular. In making their circular passes in the interaction chamber, electrons excite the resonant cavities into oscillation. A magnetron, therefore, is an oscillator, not an amplifier. A takeoff loop in one cavity provides the output. Magnetrons are capable if developing extremely high levels of microwave power. When operated in a pulse mode, magnetron can generate several megawatts of power in the microwave region. Pulsed magnetrons are commonly used in radar systems. Continuous-wave magnetrons are also used and can generate hundreds and even thousands of watts of power.

4.2 SLOTTED WAVEGUIDED 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 center frequency downwards from 2320MHz nominal to about 2300MHz. 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.

Fig.4.2 Slotted waveguide antenna


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CHAPTER 5

RECEIVER DESIGN 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. Rectennae are highly efficient at converting microwave energy to electricity. In laboratory environments, efficiencies above 90% have been observed with regularity. Some experimentation has been done with inverse rectennae, converting electricity into microwave energy, but efficiencies are much lower--only in the area of 1%. With the advent of nanotechnology and MEMS the size of these devices can be brought down to molecular level. It has been theorized that similar devices, scaled down to the proportions used in nanotechnology, could be used to convert light into electricity at much greater efficiencies than what is currently possible with solar cells. This type of device is called an optical rectenna. Theoretically, high efficiencies can be maintained as the device shrinks, but experiments funded by the United States National Renewable energy Laboratory have so far only obtained roughly 1% efficiency while using infrared light. Another important part of our receiver circuitry is a simple sensor. This is simply used to identify when the mobile phone user is talking. 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. Antenna design is important in the proposed rectenna. The antenna absorbs the incident microwave power, and the rectifier converts i t into a useful electric electr ic power. In this paper, in order to reduce the size of the rectenna, we propose to combine the BPF and the antenna into a single unit.


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5.1 RECTENNA A rectifying antenna rectifies received microwaves into DC current. A rectenna comprises of a mesh of dipoles and diodes for absorbing microwave energy from a transmitter and converting it into electric power. 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. In laboratory environments, efficiencies above 90% have been observed with regularity. In future rectennas will be used to generate large-scale power from microwave beams delivered from orbiting GPS GPS satellites.

FIG 5.1 Block diagram diagram of a rectenna with a load There are at least two advantages for rectennas: 1. The life time of the rectenna is almost unlimited and it does not need replacement (unlike batteries). 2. It is "green" for the environment (unlike batteries, no deposition to pollute the environment).

5.2 SCHOTTKY BARRIER DIODE A

Schottky barrier diode is different from a common P/N silicon diode. The

common diode is formed by connecting a P type semiconductor with an N type semiconductor, this is connecting between a semiconductor and another semiconductor; however, a Schottky barrier diode is formed by connecting a metal with a semiconductor. When the metal contacts the semiconductor, there will be a layer of potential barrier (Schottky barrier) formed on the contact surface of them, which shows a characteristic of rectification. The material of the semiconductor usually is a semiconductor of n-type Dept. of ECE SDMIT Ujire

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WIRELESS CHARGING OF MOBILE USING MICROWAVE (occasionally p-type), and the material of metal generally is chosen from different metals such as molybdenum, chromium, platinum and tungsten. Sputtering technique connects the metal and the semiconductor. A Schottky barrier diode is a majority carrier device, while a common diode is a minority carrier device. When a common PN diode is turned from electric connecting to circuit breakage, the redundant minority carrier on the contact surface should be removed to result in time delay. The Schottky barrier diode itself has no minority carrier, it can quickly turn from electric connecting to circuit breakage, its speed is much faster than a common P/N diode, so its reverse recovery time Tr is very short and shorter than 10 ns. And the forward voltage bias of the Schottky barrier diode is under 0.6V or so, lower than that (about 1.1V) of the common PN diode. So, The Schottky barrier diode is a comparatively ideal diode, such as for a 1 ampere limited current PN interface.

5.3 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. The sensor circuit is used to find whether the mobile phone using the microwaves for message transferring or not! So here we can use any Frequency to Voltage converter converter to do our job. We can use LM2907 LM2907 for F to V conversion. So when our phone is receiving microwave signal it make the rectenna circuit on and charge the battery. A simple yet powerful F to V converter is LM2907. Using LM2907 would greatly serve our purpose. It acts as a switch for triggering the rectenna circuitry. The general block diagram for the LM2907 is given below. Thus on the reception of the signal the sensor circuitry directs the rectenna circuit to ON and the mobile phone begins to charge using the microwave power.


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Fig.5.2 LM2907 The LM2907 LM2917 series are monolithic frequency to voltage converters with a high gain op amp Comparator designed to operate a relay, lamp, or other load when the input frequency reaches or exceeds a selected rate. The tachometer uses a Charge Pump technique and offers frequency doubling for low ripple, full input protection in two versions (LM2907-8, LM2917-8) and its output swings to ground for a zero frequency input. The op amp Comparator is fully compatible with the tachometer and has a floating Transistor as its output. This feature allows either a ground or supply referred load of up to 50 mA. The collector may be taken above VCC up to a maximum VCE of 28V. The two basic configurations offered include an 8-pin device with a ground referenced tachometer input and an internal connection between the tachometer output and the op amp non-inverting input. This version is well suited for single speed or frequency switching or fully buffered frequency to voltage conversion applications. The more versatile configurations provide differential tachometer input and uncommitted op amp inputs. With this version the tachometer input may be floated and the op amp becomes suitable for active Filter conditioning of the tachometer output. Both of these configurations are available with an active Shunt Regulator connected across the power leads. The Regulator clamps the supply such that stable frequency to voltage and frequency to current operations are possible with any supply voltage and a suitable resistor.


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WIRELESS CHARGING OF MOBILE USING MICROWAVE Applications of LM2907 circuit are 1. Frequency to voltage conversion (tachometer) 2. Speedometers 3. Speed governors 4. Automotive door lock control 5. Clutch control 6. Horn control

5.4 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 single diode power rectifier in “hybrid technology” with improved sensitivity at low power levels. Microwave energy transmitted from space to earth apparently has the potential to provide environmentally clean electric power on a very large scale. The key to improve transmission efficiency is the rectifying circuit. The aim of this study is to make a low cost power rectifier for low and high power levels at a frequency of 2.45GHz with good efficiency of rectifying operation. The objective also is to increase the detection sensitivity at low power levels of power. Different configurations can be used to convert the electromagnetic waves into DC signal. The study done showed that the use of a bridge is better than a single diode, but the purpose of this study is to achieve a low cost microwave rectifier with single Schottky diode for low and high power levels that has a good performance. The goal of this investigation is the development of a hybrid microwave rectifier with single Schottky diode. The first study of this circuit is based on the optimization of the rectifier in order to have a good matching of the input impedance at the desired frequency 2.45 GHz. Besides the aim of the second study is the increasing of the detection sensitivity at low levels of power. The efficiency of Schottky diode microwave rectifying circuit is found to be greater than 90%.


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CHAPTER 6

ADVANTAGES, DISADVANTAGES AND APPLICATIONS

6.1 ADVANTAGES

1. Charging of mobile phone is done wirelessly 2. We can saving time for charging mobiles 3. Wastage of power is less 4. Mobile get charged as we make call even during long journey 5. Only one microwave transmitter can serve to all the service providers in that area. 6. The need of different types of chargers by different manufacturers is totally eliminated.

6.2 DISADVANTAGES 1. Wireless transmission of the energy causes some effects to human body, because of its radiation 2. Network traffic may cause problems in charging 3. Charging depends on network coverage 4. Rate of charging may be of minute range 5. Practical possibilities are not yet applicable as there is no much advancement in this field. 6. Process is of high cost

6.3 APPLICATIONS 1. As the topics name itself this technology technology is used for for “Wireless charging of mobile phones”. Dept. of ECE SDMIT Ujire

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CHAPTER 7

CONCLUSION 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. 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.


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CHAPTER 8

REFERENCES 1.

Theodore.S.Rappaport, “Wireless Communications Principles and Practice”. Practice”.

2. Wireless Power Transmission – Transmission – A A Next Generation Power Transmission System, International Journal of Computer Applications Volume 1 – 1 – No. No. 13. 3. Lander, Cyril W. "2. Rectifying Circuits". Power electronics London: McGrawHill. 3rd edition, 1993. 4. Tae-Whan yoo and Kai Chang, "Theoreticaland Experimental Development of 10 and 35 GHz rectennas" IEEE Transaction on microwave Theory and Techniques, vol. 40. NO.6. June.1992. 5. Pozar, David M. Microwave Engineering Addison – Wesley Wesley Publishing Company,1993. 6. Hawkins, Joe, etal, "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.


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wireless mobile charger report.pdf

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