Wireless Power TransmissionUsing Microwaves  Abstract:      Various new technologies are beingdeveloped for transmitting power through wireless systems and one of the ways oftransmitting electricity without wire is through the microwave transmission.The process of transmitting the power by using microwaves is called as MicrowavePower Transmission(MPT). This will cause reduction in the transmission anddistribution losses.

Rectenna is a device used to convert the microwaves intopower for the MPT system. This paper will give the idea about impact on humanbeings, advantages, disadvantages, & applications of wireless powertransmission.Keywords: Wireless power transmission (WPT),Microwave power transmission (MPT), Wireless Sensor network(WSN). Introduction:        Wireless power transfer (WPT) is thetransmission of electrical power from a power source to a consuming devicewithout using manmade conductors. For long distance transmission without using wiresresearchers have developed several techniques for moving electricity. There aresome exists only as theories or prototypes but others are already in use.

Thispaper provides the techniques used for wireless power transmission. It is ageneric term that refers to a number of different power transmissiontechnologies that use time varying electromagnetic fields. Wireless transmission is useful topower electrical devices in case where interconnecting wires are inconvenient,hazardous, or are not possible.

For example the life of WSN is its node whichconsist of several device controllers, memory, sensors, actuators, transceiversand battery and battery. The transceiver can operate in four states, i.e 1)Transmit 2) Receive 3) Idle and 4) Sleep. The major energy problem of atransmitter of a node is its receiving in idle state, as in this state it isalways being ready to receive, consuming great amount of power.

 However, the batter has a very short lifetimeand moreover in some developments owing to both practically and economicallyinfeasible or may involve significant resists to human life. That is why energyharvesting for WSN in replacement of battery is the only and unique solution.In wireless power transfer, a transmitter device source, such as the mainspower line, transmits power by electromagnetic fields across an interveningspace to one or more receiver devices, where it is converted  to electric power and then utilized.The goalof the communication  is the transmissionof information, so the amount of power reaching the receiving antenna isunimportant till  signal to noise ratiois high enough so that the information can be received intelligibly. In wirelesscommunication technologies, generally, only little amounts of power reach thereceiver. By contrast the amount of power received is the important thing, sothe efficiency (fraction of transmitted power that is received) is the moresignificant parameter.MICROWAVEREGION Figure 1.

1 Microwave Region of ElectromagneticSpectrumThe figure 1.1 shows that themicrowaves are the radio signal which has the wavelength array of 1 mm to 1meter and the frequency is 3000 MHZ to 300 GHZ. Microwaves contain wavelengththat preserves is calculated in centimeters microwaves are good quality fortransmitting information from one place to another place because microwaveenergy be able to penetrate haze, snow, clouds, light rain, and smoke.Microwave radiation is still connected with an energy level that is typicallynontoxic except for people with pacemakers.

EXISTING METHOD Possible methods of wireless transmission ofelectrical power A.Inductive coupling B.Laser  C.Radio frequencyD.Microwave A.

Inductive coupling In this whentransmitting coil is excited then it generates flux and when receiver coilreceives this flux a potential difference is developed across its terminal.This is the basic model and its efficiency is very poor hence cannot be usedfor large distance transmission.B.LaserIt is a devicewhich emits light based on the stimulated emission of electromagneticradiation. Power can be transmitted by means of converting electricity keen onlaser beam.

But in this laser radiation is hazardous and conversion betweenelectricity and light is ineffective.C.Radio frequencyRadio frequencysignals to direct current electrical current powered from either aninternational or ambient power sources.  PROPOSEDMETHOD:The figure 1.2 shows that the purposeful block diagramof WPT consists of two sections: transmitting section and receiving section. In thetransmission section, the microwave power source generates microwave powerwhich is prohibited by the electronic control circuits. The waveguidecirculator protects the microwave resource from the reflected power, which isconnected through the co-ax waveguide adaptor.

The tuner contests the impedancebetween the microwave source and transmitting antenna. After that, based on thesignal broadcast direction, the  signalsare separated using directional coupler. The transmitting antenna sends thepower frequently through open space to the receiving antenna.

 In thereceiving side, the  receiving antenna observesthe transmitted power and converts the received microwave power into DC power.The filter and impedance matching circuit  is provided for locating the harvest impedanceof a signal source which is equivalent to rectifying circuit. The circuitconsists of Schottky barrier diodes that converts the microwave power keen onDC power.

Working:  A rectenna is arectangular antenna with rectifying circuit,It is a type of antenna that isused to convert microwave energy into DC current. It’s elements are usuallyarranged in a mesh pattern, to provide a distinct appearance from mostantennae.A simple rectenna can be constructed using a Schottky diode placedbetween antenna dipoles. The diode (a uni direction device)is used to rectifythe induced current in the antenna by the microwaves signals. Rectenna is highlyefficient for converting microwaves into electricity. In laboratoryenvironments, efficiencies above 90% have been observed.

Scientists also triedto convert electricity into microwave energy using inverse rectenna, butefficiencies are very low. only in the area of 1%. With the advent ofnanotechnology and MEMS the size of rectenna elements can be brought down tomolecular level.

A rectenna contains a mesh of dipoles and a mesh of diodes forabsorbing microwave energy from a transmitter and converting it into electriccurrent.RECTENNADESIGNIn emergent this design, the PBG antenna, DGS LPF, andrectifier circuits were every first fabricated, designed, and characterizedalone.  The rectenna isa passive element which consist of antenna, rectifying circuit with a low passfilter between the antenna and rectifying diode.Schottky Brrier diodes(GaAs-W, Si, GaAs) are usually used in therectifying circuit due to the fast reverse recoery time and lower forwardvoltage drop and good RF characteristics.The rectenna efficieny for variousdiodes at different frequency is shown in table 1.

1. Frequency (GHz) Schottky Diode Measured Efficiency (%) Calculated Efficiency (%) 2.45 GaAs-W 92.5 90.5 5.8 Si 82 78.5 8.

5 GaAs 62.5 66.2 Table 1.1 Rectenna Efficieny For Various Diodes at Different Frequency             Figure 1.3 Rectenna Design The figure 1.

3 shows the rectenna used in the project.Rectenna has divided two copper plates with Schottky diode which acts as aresistor between two plates. Likewise, we have positioned 10 setups in parallelsuch that we have placed 10 resistors in parallel which intone act as theconductor with high absorption power since resistors in parallel act as aconductor. RESULTSTable 1. 2 Distance Covered Vs Voltage S.No Distance(cm) Voltage(volts) 1 35 32 2 50 30 3 65 22 4 80 18 5 100 8        In table 1.2 we have presented thewireless power transmission which displays that increase in distance leads todecrease in voltage.

This decrease in voltage is due to distortion of microwavesin the air medium.                       Figure 1.8 Distance Vs Voltage Curve          In figure 1.8, the graph is drawn betweenthe distance and voltage.

If the rectenna is nearer to the transmitter, thevoltage level absorbed by the rectenna is high up to 32V.If the distance isincreased between the transmitter and receiver, the          Voltage level decreased. VI.ADVANTAGES AND DISADVANTAGEA.ADVANTAGES1.   Entirely eradicate the existing high-powertransmission line towers, cables etc…2.

   The transmission and distributioncost become less3.   Hence, the efficiency of this methodis very much higher than wired transmission.4.   The power failure as a result ofshort circuit and fault of cables would never be present.5.   The power can be transmitted to theplaces where the wired transmission is not a feasible.6.   Capability to charge vehicles such asindustrial vehicles and golf carts.

7.  Substantiateand alter  to loads B.DISADVANTAGE  1.  Production and development is still underprocess.

2. It does not give sufficientenergy to charge enormous vehicles and types of equipment.3.

  Transmitting distance is unreliable4. Heat energy is lost during the transmission.5. Intervention of microwaves with apresent signal.  VII.APPLICATIONS1.

     Used in cordlesstools, automatic wireless charging for mobile robots and instrument thiseliminates complex mechanism.2.     Easy and neatInstallation – there is no cable running here and there, just start up thewireless device.

3.     Mobility -within the wireless range user device can be moved easily.4.     The ability of our technology to transferpower efficiently, safely and over distance can improve products by making themmore reliable, convenient, and environmentally friendly.    VIII.

CONCLUSION Wireless Power Transmission (WPT) wassuccessfully achieved up to the distance of 1 meter and beyond with the help ofthe high power rectenna and proposed with higher lumens. It is difficult tofind inductors and capacitors that are capable of working at higher powerlevels. However, safety is needed to be concern for the further extension ofthe project and modification is required for higher end design. Configurationon the cost factor and design constraints, including noise factor are to beconsidered and suggested to concern for the further development.