Wireless Power Transmission - Essay Example

Wireless Power Transmission Insert Insert The advancements witnessed in the field of technology are meant to make life simpler. The next technology, to keep watching out for, is the use of wireless power transmission ability. The report described here gives a detailed account of how it is possible to tap energy from the power source and transmit it in the air to the load/ destination device. Moreover, the research project enlarges the view and knowledge of wireless systems. List of tables Table 1 components used in the transmitter 49 Table 2components used in the receiver circuit 55 List of figures Figure 1. Wave propagation 8 Figure 2 propagation of electromagnetic wave 9 Figure 3 wave propagation with loss 11 Figure 4. Standing wave accelerating graph 17 Figure 5. Wave accelleration and deccelleration 18 Figure 6. Transmitter coil 28 Figure 7. Transmitter coil 28 Figure 8. Optimum link efficiency 32 Figure 9 WPT 33 Figure 10 WPT and image 34 Figure 11 coil 35 Figure 12. Qi system 38 Figure 13 Qi system 38 Figure 14.Qi system 38 Figure 15 Placement of coil 39 Figure 16. Product of the coupling factor and the quality factor 42 Figure 17 Block diagram of the transmitter module 47 Figure 18 schematic diagram of the transmitter module 48 Figure 19 complete transmitter circuit 50 Figure 20 Receiver module 50 Figure 21. Diode bridge rectifier 52 Figure 22 positive rectification wave 53 Figure 23 negative wave rectification 53 Figure 24 smoothing capacitor in rectification 54 Figure 25 Circuit diagram of the receiver module 55 Figure 26 Receiver Simulation 56 Figure 27 Receiver simulation display 57 Figure 28 Receiver simulation display 57 List of equations …………………………………………………………..Equation 1 12 ………………………………………………………….2 gauss electric fields 12 ………………………………………………………………………..3 12 ………………………………………………………...4 13 …………………………………5 13 ……………….6 link efficiency 30 ……………………………………………………………………7 30 ……………………………………………………………………8 30 ………………………………………………………….……...9 30 ……………………………………………………………..10 31 ………………………………..11 31 …………………………………………………………………12 32 …………………………………………..…….13 32 ……………………………………………………………14 40 ………………………………………………………………………...15 40 ………………………………………………………………………………………..16 40 ………………………………………………………………..17 41 ……………………………………………………………………18 41 …………………………………………….…..19 42 ………………………………………………………………..20 49 ……………………………………………21 49 ………………………….............22 49 ………………………………………………………………..23 51 Contents Wireless Power Transmission i Abstract ii List of tables ii List of figures iii List of equations iv Contents v Introduction 1 Aim 1 Literature review on electromagnetism 2 Overview 2 Inventors 4 Michael Faraday 4 Fundamental forces 5 Classical electrodynamics 5 Photoelectric effect 6 Quantum electrodynamics 6 Electroweak interaction 7 Electromagnetic propagation 7 Propagation of an electromagnetic wave 9 Maxwell’s equations and electromagnetic propagation 12 Special relativity 14 Antennas and types of antennas 19 Performance 19 Resonant antennas 20 Antenna design criteria 20 "Rabbit ears" set-top antenna 20 Current and Voltage Distribution 21 Bandwidth 23 Gain 23 Efficiency 24 Impedance matching 26 Basic antenna models 27 Types of coil used for transmitting power wirelessly 28 Introduction 28 Link efficiency 30 Evaluating the electromagnetic induction method 33 Various coil shapes 34 Various size coils 34 Application note 35 Close – coupled Qi Standard Wireless Power Consortium (WPC) 36 Loosely-coupled (LC) Wireless Power Transfer (Magnetic Resonance) the Alliance in the Wireless Power Transmission 36 Power Matter Alliance (PMA) 37 The Qi system 37 Key factors for the coils 39 Improvement and optimization of the standard coils 43 Summary 43 Choice of the antenna substrate 44 Choice of antenna 44 Choice of the fabrication method 45 Benchmarking prototype 45 Conclusion 46 Methodology 46 Transmitter module 46 Transmitter coil 49 Components used in the transmitter 49 Receiver module 50 Receiver Coil 50 Rectifier 51 Smoothing capacitor 53 Voltage regulator integrated circuit 54 Circuit diagram of the receiver module 55 Performance and analysis 56 Safety features 57 Discussion and Recommendation 58 List of References 62 Appendixes 66 Electromagnetic wave MatLab code 66 Receiver simulation report 67 Introduction The current world with the advancement has seen the development of devices that make life for human beings simpler. According to Zhang, R. and Ho, “Wireless power transfer (WPT) is a promising new solution to provide convenient and perpetual energy supplies to wireless networks” [54]. Current charging systems make use of the classical wired systems. Low power devices that include mobile phones and digital cameras use batteries which are charged. In cases where one has many low power devices and intends to charge them simultaneously, it becomes a tedious affair. Current manufacturers make electronic gadgets with varying charging systems. To curb the messy picture of using wired systems, wireless power transmission comes handy and an effective way to charge portable and low-power gadgets. Aim This report will examine methods of connecting two or more devices wirelessly to power them up, the design of electromagnetic transceiver to enable powering the device in multiple direction. Objectives: 1- Theory about electromagnetism. 2- Ways of transmitting wirelessly. 3- Electromagnetic propagation. 4- Types of antenna to radiate wireless power efficiently. 5- Types of coil used for transmitting power wirelessly. 6- Omni-directional wirelessly conductivity. 7- Simulation via Proteus or MATLAB software. Literature review on electromagnetism Overview Electromagnetism is considered to be the study of physical interaction occurrences placed between electrically charged elements. The power of electromagnetism manifests as a field, which is one of the major four fundamentals in nature’s interactions leaving the other three as gravitation, weak interaction, and strong interaction. “WPT is carried out using either the “near-field” electromagnetic (EM) induction (e.g., inductive coupling, capacitive coupling) for short-term distance (say, less than a meter) applications such as passive radio-frequency identification (RFID) [3], or the “far-field” EM radiation in the form of microwaves or lasers for long-range (up to a few kilometers) applications” [54]. Lorentz force is an electromagnetic phenomenon which including both electric and magnetic elements of a single phenomenon. The force of electromagnetism plays a significant role in the determination of the functions of the objects we encounter every day . Ordinary things then aquire the form resulting from intermolecular forces that are between the individual matter molecules. Electrons are bound by electromagnetic wave mechanics to form building blocks of molecules called atoms. It is possible to define the interactions between the electrons of neighboring atoms by the contact of electromagnetic power and the momentum of the electrons. Electromagnetic field has a lot of mathematical descriptions. In classical electrodynamics, a description of electric fields is of an electric potential and of a subsequent electric current in Ohms law. The association of magnetic fields with magnetism and electromagnetic induction, and a description of Maxwells equations on the generation of electric and magnetic fields are prescribed an altercation by each other and by the current charges. Albert Einstein in 1905 developed special relativity due to the establishment of speed of light based on properties of the medium. Although the consideration of electromagnetism is of one of the fundamental four forces, a unison of the electroweak forces at high energy is possible. The split of the electroweak forces is during the quark epoch into the weak and electromagnetic force. Originally the thought of electricity and magnetism were of as two distinct forces until James Clerk Maxwell Treatise in 1873 on Electricity and Magnetism proposed the regulation in the interaction between the negative and positive charge by a single force. The four main effects of the resultant interactions were clear on experimental demonstrations: Like charges, attract one another while unlike charges repel each other with a force of inverse proportionality to the square distance separating the two. The attraction to the repulsion of the poles of a magnet and to each other in a similar manner always comes in pairs similar to the yoking of every North Pole to a south pole. The creation of a circular magnetic field by an electric current carrying wire and its direction of focus are dependants on that of the current. The induction of current is looped on the wire during its movement to or from the magnetic field with the current direction being dependent on this movement. On 21 April 1820 HAN Christian orsted realized something a compass needle diverged from magnetic north when electric current was put on. The realization convinced him that the magnetic field radiates from all direction on a wire carrying electric current. Inventors Michael Faraday He didn’t represent the phenomenon in a mathematical framework until after three months when he began his investigation. He later published his findings that electric current produce a magnetic field as it flows through a wire. The findings led to magnetic induction made (oersted) honor him. James Clerk Maxwell His findings made the famous physicist Andre-Marie Ampere’s theoretical developments concerning a single mathematical form to a representation of the magnetism forces between conductors carrying currently. orsteds discovery made a major step in a unified concept of energy. Mathematical physics was accomplished in the 19th century due to the unity of Michael Faraday, James Clerk Maxwell, Oliver Heaviside and Heinrich Hertz. Unlike the proposition in light, electromagnetism, and other waves of electromagnetism that are at the present seen as taking the form of self-propagating, quantized, and oscillatory disturbances of electromagnetic fields now known as photons. The frequency difference in oscillation gives rise to the different types of electromagnetic forms of radiation. The forms are from the lowest frequency radio waves to the intermediate frequencies giving rise to visible light, and to the highest frequencies gamma rays. In 1802 not only did orsted saw the relationship between electricity and magnetism, but also Gian Domenico Romagnosi he deflected a magnetic needle by electrostatic charges. No electromagnetic was there since there was no galvanic current existing in the setup. It was published in an Italian newspaper, but the scientific community overlooked it. Fundamental forces Apart from the electromagnetic force there are three other fundamental forces. Weak nuclear force responsible for radioactive decay, strong nuclear responsible for holding the nuclei atoms together and the last begin gravitational force. The force of gravity might be weak but very long in range, and it acts between two pieces of matter. Intra-atomic to intermolecular forces is generated by electrons carrying momentum with them. According to Pauli Exclusion Principle the behavior of matter at the molecular scale levels with an inclusion to its density is a determination of the balance between electromagnetic forces and the force generated. Therefore, as the electrons are confined, their minimum momentum increases. Classical electrodynamics William Gilbert in his De Magnete (1600) proposed that electricity and magnetism were both capable of causing attraction and repulsion of objects with distinct effects. In 1752, Benjamin Franklin proposed an experiment to find the relationship between lighting and electricity after some marines notice lighting strike have an effect on compass needle. In 1802, Romagnosi discovered a relationship between man-made electric current and magnetism. The effect was not well and widely known until the performance of a similar experiment in 1820 by orsted. Generally many physicists developed classical electromagnetism in the 19th century. James Clerk Maxwell finalized by developing one theory and discover electromagnetic nature of lights. He explained that the electromagnetic field obeys a Maxwell’s equation, and electromagnetic force was given by Lorentz force law. Classical electromagnetism is difficult to reconcile with classical mechanism. According to Maxwell’s equations, the travel speed of a light wave through a vacuum is constant it depends on the electric nature of permittivity and the magnetic nature of permeability in free space. This contradicts Galilean invariance a long-standing cornerstone of classical mechanics. The only solution to the reconciliation of the two theories is by assuming the existence of an a luminiferous aether through which the light propagates. However, many experiments have failed to detect its presence. Albert Einstein gave a solution to the problem in 1905 with the kinematics theory that is compatible with classical electromagnetism. Relativity theory tries to ascertain that by the movement of reference frames, the transformation of a magnetic field is towards a field possessing an electric component with a nonzero attribute and vice versa. Photoelectric effect In 1905, Albert Einstein came up with another theory of the photoelectric effect he said light could exist in particle-like quantities which was later known as photons. Max Planck in 1900 stated that hot objects produce electromagnetic energy in separate packets. It disproves the standard definition of light as a continuous wave. As a result quantum theory of electromagnetism was created in 1940s- 1950s. Quantum electrodynamics Quantum mechanics supports all electromagnetic phenomena especially quantum electrodynamics, and this is almost all physical phenomena which can be needed by human sense i.e. light and other electromagnetic radiation. Electroweak interaction It’s a combination of two main interactions such as electromagnetism and weak interaction. Notwithstanding that the two powers are not the same at everyday low energy they is combined into a separate electroweak power. Thus, electromagnetic power and the weak power turn into the one electroweak power if the universe is hot. During epoch electroweak power disconnect from a strong power at the same time as in quark epoch the electroweak power is divided into the electromagnetic and a weak power. Electromagnetic propagation Magnetic propagation can be illustrated by an example of a vertical wire carrying an alternating current that generates an electric field. The generated magnetic field change, that generates a subsequent electric field, is from an original electric field. The fields are successfully induced; that is from electric to magnetic to electric, leads to magnetic propagation. To generate and propagate a magnetic field, first magnetic field force is required. This can result from producing a changing field by turning on an electromagnetic or removing a magnet from a magnetic shield such as superconducting box. The electromagnetic propagation, that composes electromagnetic radiation, can be seen as self-propagating transverse oscillating wave of electric and magnetic fields. The diagram below shows a plane nearly Polarized Electromagnetic radiations with wave propagation from the left to the right. The fields as a consequence of electricity and magnetism are in a vertical plane and horizontal plane respectively. The electric field is always in phase with the magnetic fields in Electromagnetic radiation (EMR) waves and is perpendicular to each other. Figure 1. Wave propagation Electromagnetic radiations represent a kind of energy produced by electromagnetic course. In physics, all EMR is connected with light, but light is connected with visible light. EMR involves electromagnetic waves that of synchronized oscillations of magnetic and electric fields’ transmition synching with the movement of a light wave. The areas’ oscillations are perpendicular to each other, the wave’s propagated direction and the direction of energy transmition. The areas are also at right angles to each other creating a transverse wave. The electromagnetic waves are distinguished by the wavelength or the regularity of their oscillations to create the electromagnetic field. The magnetic field involves the order of rising frequency and lowing wavelength. Microwaves, ultraviolet, radio waves, infrared waves, , x-rays, gamma rays, visible light can serve as examples. The electromagnetic waves are created if charged elements are intensified and can communicate with any charged particles. The EM is influenced by the gravity. Electromagnetic energy is connected with the electromagnetic waves, which have mobile transmition to themselves without the influence of the moving charges that create them; this was due to the reason that they have reached enough space from the charges. Propagation of an electromagnetic wave Electromagnetic field E Z B Discharging Spark Magnetic field Electric field Electromagnetic waves can be generated through various methods such as discharging a spark. Electromagnetism involves oscillating magnetic fields and electric fields whose amplitudes and directions are represented by vectors that undulate in phase in the two mutually perpendicular planes. The figure shows propagation of a virtual electromagnetic wave and considers orientation of the magnetic and electric field vectors. By discharging the spark from a virtual capacitor, the electromagnetic wave is generated. The oscillation of the spark is at a characterized frequency resulting to the disturbance of the electromagnetic propagation. The magnetic (B) and electric (E) field vectors vibrate perpendicularly to each other and to the direction of propagation (z). The wavelength emitted in by the virtual capacitor discharge can be altered by using the wavelength slider. If a spark is discharged due to charging of the capacitor, the current induced by the spark flows down for a short time, but because of the induction of the circuit, it flows back and recharges the capacitor again. This propagation of an electromagnetic wave, which is generated by discharging the capacitor is shown in the figure above. When the current oscillates up and down in the spark gap, a magnetic field oscillating at a circuit frequency is created in a horizontal plane. The magnetic field changes in turn induces an electric field so that a series of magnetic and electric oscillations come together to produce a formation that propagates as an electromagnetic wave. Figure 3 wave propagation with loss The electric (E) and the magnetic (B) reflect the amplitude and the vibration direction of the two waves which are oriented perpendicularly to the direction of the wave propagation and to each other. The resulting electromagnetic wave velocity can be obtained from the relationships of the magnetic and electric field interactions. This is obtained from Maxwell equations that prove the relationship between velocity and the speed of light in a vacuum.(c is 300000 kilometers per hour ) with a division to the square root of the medium’s dielectric constant (k) multiplied by the given medium’s magnetic permeability (m) and other equations related to magnetic propagation. Thus, …………………………………………………………..Equation 1 Maxwell’s equations and electromagnetic propagation Maxwell has four equations that analyze the electric and magnetic fields that cause the propagation. The equations arise from varying distributions of magnetic and electric changes and currents, and how those fields change in time. The equations were drawn from experimental observations after decades of study on the electric and magnetic effects of charges and currents. Maxwell equations made evident that varying magnetic, and electric fields feed off each other and the propagation of the fields proved indefinite through space, far from where the currents and charges had originated from. The equations are as follows; 1. Gauss’ electric fields law: ………………………………………………………….2 gauss electric fields (The outgoing integral of an electric field over a volume enclosed by an area equals the total change inside, in appropriate units) 2. The corresponding formula for magnetic fields; ………………………………………………………………………..3 (No magnetic charge exists; no “monopoles”) 3. Faraday’s Magnetic induction law; ………………………………………………………...4 The integrated first term is around a closed line, which is a wire and gives the total voltage change around the circuit; this is caused by the varying of the magnetic field through the circuit. 4. Maxwell’s displacement current plus Ampere’s law. …………………………………5 This gives the total magnetic force in terms of the current around the circuit through the same circuit (that’s the “displacement current”) This paper looks at the three equations to show why the displacement of current should be added for consistency and using differential equations, how measured values of electric and magnetic attraction are able to determine the speed of light. The first equation of Maxwell represents the surface with large patches having little areas which are small enough to be regarded as flat. The vector magnitude  is just the area’s value; the vector’s direction is perpendicular to the area element pointing towards away from the enclosed volume. This is the only component of the flux that leads to actual electric flux across the surface. The field vector represents the direction and the velocity of the flow. The second equation is one of the magnetic fields that have no sources or no magnetic monopolies. Magnetic flux is taken as force lines which are used to represent a kind of fluid flow. The equation can be clearly visualized as magnetic flux that flows in and out of a closed surface from two distinct surface points. Thus the enclosed volume’s net flux is zero. Special relativity Magnetic fields are relatively distortions of electric fields. When the two fields are combined they form a propagating electromagnetic wave, which goes to space without affecting the source again. This far distance electromagnetic area created in this way by speeding up charge carries with its energy through space therefore the term far fields [36]. Electromagnetic areas involve the far part of the electromagnetic field around the transmitter. The neighboring field creates the section for altering the electromagnetic area, however, it does not count as electromagnetic energy. Maxwell equations demonstrated that some charges and currents made local form of the electromagnetic area near the currents. These currents do not behave as electromagnetic. Maxwell showed that currents straightforwardly create magnetic area and they are of a magnetic dipole that dries quickly with distance from the current. Similarly, moving charges when alienated from each other in a performer by an altering potential, create an electric field, but this also disappear necessary with space. This two areas’ result to neighboring area near the EMR source and neither of this behaviors are responsible for the EM radiation. On the other hand they provoke electromagnetic field behavior that only influences the transfers of energy to a recipient very close to the source. A transformer’s magnetic induction and a metal detector’s feedback behavior that occurs close to its coil as examples. The near fields influence strongly on their own sources causing an increased load in the transmitter anytime the energy is taken from the electromagnetic field by a receiver. Basically, these fields do not propagate freely out at space. They can carry their energy away without the limit of the distance, but they oscillate forth and back to the transmitter. The far field has radiation and is free of transmitter, unlike the near field. The transmitter needs the same power as in the near field to send the changes in the far field out, whether the signal is picked up immediately or not. The electromagnetic field is the electromagnetic radiation and also the far-field. This electromagnetic radiation (far-field) is transmitted without any effect of the transmitter and this ensures them to be independent in the sense that their energy and existence, after the electromagnetic radiation leaves the transmitter, is gains complete independence of both the transmitter and the receiver. It is possible because the waves conserve their transmitted energy through any drawn spherical boundary surface circumscribing their source. The dipole part of the near fields varies in power according to the inverse cube power law thus does not carry conserved amount of energy over distances which results to their rapid death with distance by its energy rapidly returning to the transmitter or absorbed by the nearby receiver, an example of a receiver is transformer secondary coil. The electromagnetic energy, which is also the far-field, counts on a different instrument for its generation as judged against to the near field and upon different terms in Maxwell equations. Magnetic part of near field is by the currents in the source, but in far-field, the magnetic part is due only to the local alteration in the electric area. The electric field in far-field is as a consequence of the change in local magnetic field while, in the near field, the electric field is as a result of charge separation in the source. All these processes for generating electric and magnetic fields have different dependence on the distance with the far field having more power over long distances compared to the near fields. The term “far” refers to the distance from the source at the speed of light to a portion of the outward moving EM field’s location, to the time change of the source currents by the variation of the source potential. Thus, electromagnetic wave can be considered as self-propagating and transverse to the wave oscillation of the electric and magnetic fields. Common terms used in the magnetic propagation and their meaning 1. Electromagnetic propagation. Is an interaction between electricity and magnetism which result from changing magnetic field generating an electric field and vice versa. 2. Magnetic field. Is a region acted upon by a magnetic force as a result of moving electric charges around a magnetic material? 3. Electric field. Is a region around a charged particle within which an exerted force is on the other charged particles. 4. Longitudinal wave. Is the vibration of a wave in a propagated direction. 5. Transverse wave. Is the vibration of a wave at right angles in a propagated direction. 6. Wavelength. The successive distance between wave crests especially electromagnetic wave. 7. Amplitude. Is the maximum extent of a vibration or oscillation, measured from a position of equilibrium. 8. Oscillation. Is regular vibration in magnitude or position around a central point. 9. Is the vibration occurrence rate that constitutes a wave in an electromagnetic field, usually measured in terms of per second. 10. Velocity. Is the speed of the electromagnetic wave in a given direction. 11. Magnetic flux. Is a measure of quantity of magnetism. Is the summation of magnetic force lines traversing through a magnetic field’s enclosed area. The direction of beam propagation is called longitudinal direction. The cross-sectional plane has two directions perpendicular to the direction of the propagation referred to as a transverse direction. The graph below illustrates the same. Y (Transverse direction) X (propagation direction) Figure 4. Standing wave accelerating graph The graph below is used to show standing electromagnetic waves, which act on particle acceleration. To work as an accelerator, the electric field must be along the direction of beam propagation. The electric field is driven by sinusoidal voltage thus the polarity of the electric field will be accelerating half the time, and the rest of the time the field is oriented to ensure it decelerates. Y-axis Amplitude X- Axis 0 Deceleration Time An antenna is considered to be one of the electrical device in charge of converting electrical power to radio waves and vice versa. It’s a component of essential importance to all radio equipment. The use of antennas includes radio broadcasting systems, communication receivers systems, broadcast television systems, cell phone systems, and satellite communications systems. It consists of metallic conductors (elements), electrically connected to the recipient or transmitter. A recurring current of electrons strained through the antenna by a transmitter generates a periodic magnetic area around the antenna parts. The charge of the electrons also generates a recurrent electric area along the parts. The areas radiate away from the antenna into space as a electromagnetic area waves and at the reception. The force exerted on the antenna’s electron elements is from an incoming magnetic field’s radio wave, causing their back and forth movement, which creates currents in the antenna Antennas and types of antennas Antennas are designed to transmit and receive radio waves in all or a particular direction. Radio waves are a kind of electromagnetic waves, which transfer signals through the air at the pace of light with the propagation losses close to null. Radio recepients and transmitters are applied in revealing data in systems including radio, mobile telephones, Wi-Fi (WLAN) data networks, trunk lines, remote controlled devices such as garage door openers, wireless remote sensors, etc. In each case scenario, the involvement of the transmitters and receivers require the presence of antennas. There are two types of antennas: Omnidirectional antennas which receive and radiate in all directions and directional antennas. Omnidirectional are used when the position of the other station can’t be revealed and also at lower frequencies where the use of a directional antenna leads to a size disadvantage and cut costs that arise in the creation of the applications, which do not need a directional antenna. Directional antennas are applied to radiate preferentially or receive in a directional pattern. Performance The process of product or system design often overlooks the Antennas even though they begin and end the circuit for a receiver and transmitter respectively. The antennas generally set the performance guidelines needed by other components in a system. An antennas basic functions are simple; radiating and receiving generated and processed signals by the other system components. The complexity in the modulation on many modern signals assists the antennas in handling those signals with the least distortion, although even the best-designed antennas subject themselves to the variations from the "ideal" design, the viewed result is due to manufacturing tolerances. Resonant antennas It’s a form of a tuned circuit made up of capacitance and inductance as the circuit’s characteristics, and resonant frequency being a result. The inductive and capacitive reactance cancel out at this frequency. The RF antenna appears at this point to be purely resistive, the consequence being a combined loss in resistance and radiation. The physical properties and the environmental location determines an RF antenna’s capacitance and inductance. A lower resonant frequency is achievable by the use of a larger antenna or more strictly just its elements. Antenna design criteria "Rabbit ears" set-top antenna This is an indoor antenna, and it is not as effective as the outdoor one. They are less directional and don’t necessarily need to be adjusted to the channel direction. They are dipole antenna making it less effective as the antennas design to maximize the signal from a narrow angle in one direction. Directional antennas are made up of a lot of multiple conductive elements that are arranged. The signal wavelength estimates to twice the length of the elements. Meaning the length of each element corresponds to a certain frequency. In a combination VHF/UHF antenna the longer elements are at the antenna’s back, in relation to the directionality of the device, and the front occupied by the much shorter UHF elements, the pointing of the antenna to the source signal being received works best. The smallest elements in the design, in the front location, use Yagi antenna principles and are UHF. The use of VHF Log-periodic principles is by the longest elements in the back location. Antenna gain is a measure in the ratio of the received signal from a direction of preference to an ideal Omni-directional antenna signal. The inverse proportionality of the gain is to the acceptance angle of the antenna. The setup and connection of two or more directional rooftop antennas to a single receiver is a possibility. Current and Voltage Distribution The current of the half wave dipole voltage maximizes at each end and minimizes towards the center. The design of the folded dipole antenna is from λ/2 of each operational frequency of two parallel conductors. The parallel conductors at the ends are joined together. The provision of an input to the folded dipole is by cutting and connecting a feeder on a select of the conductors from the center point. The main uses are mostly for the television reception, transmissions, and Frequency Mode transmissions. The efficient use of twin wire cables with transmission lines is due to the value of 300 nΩ as the input impedance for the folded dipole. Maximum power transfer propagates proper matching between the source and the load. The long wire antenna comprises of a horizontally placed conducting wire place with the help of mast or poles, and the support of springs and an insulator. The provision of an input is from a single end, and the other end of the long wire antenna provides a termination to the characteristic impedance. The characteristic impedance termination, therefore, yields proper matching preventing a feedback of the reflected energy from the load towards the source. The incident wave equals the standing waves. The voltage and current waveforms predict a unison phase to each other. The long wire antenna’s field pattern shows the unidirectional propagation of the antenna taking place. The conclusion translates to a unidirectional antenna. The lack of energy reflected from the load towards the source describes the type of long wire antenna with a termination to its characteristic impedance as a non-resonator antenna. Long wire antenna consists of horizontally placed conducting wire with the aid of mast or poles, and some support from an insulator and a spring. The provision of input from one end of the long wire antenna and also on the other end is kept on non-connection. The connection of the long wire resonant antenna provides input from one end as the other end has no connection to anything. Therefore, the incident and reflected waves are both to be present over it. The indication of the transmission efficiency is to be carried out along the horizontal axis from both sides. The bi-directional antenna is the long wire resonant antenna. An isotropic antenna radiates equally in all direction, and this is said to be the type description. The type of antenna is taken as a reference in relation to the propagation of E.M waves calculations of the Ferrite Rod Antenna. Therefore, it is considered as an ideal antenna. The input purposes find use from the open ends of the coil. The high Q of the output finds gain from positioning the former around the ferrite rod. The E.M wave’s magnetic flux in the present surroundings finds effective concentration by the use of ferrite rods. The induced maximum field in the coil to a subsequently induced voltage develops an output signal for the reception. The Q factor can only be reduced if the size of the ferrite rod is smaller than that of the coil. The disturbance of the coil’s Q factor is determined by the size of the ferrite rod in relation to the size of the coil such that it should not be longer in order to avoid a high sharpness of the Q factor. To obtain maximum output signal at the output, the coil should adhere to λ/4 distance of the desired ferrite rod frequency. The rhombic antenna consisted of two tilted conducting wires at a 70 degrees angle and positioned in a way leading to the adoption the algebraic figure of a rhombic shape. The provision of input is from one side of the wire, and the output end terminated with its characteristics impedance for proper matching by the help of a pure resistor. The resistor value varies from 600 Ω to 800Ω and its rating of power at about 2 watts. The rhombic antenna is classified as a unidirectional antenna such that its directivity is of a higher rating. It is the main use mostly for transmission purposes [41]. Bandwidth The definition depicts stored energy to the dissipation of energy per radian of oscillation. It is clear that the radiated energy takes the dissipation part in the antenna. The near field region of the antenna’s structure holds the stored energy. The minimization of the energy amount whose storage is in the antennas near field region structure will lead to a smaller Q for a given radiated energy. Moreover, the prediction is as a consequence of the fractional bandwidth (delta f)/f having a direct relation to the reciprocal of the Q factor in the circuit. One way, one can use to achieve this, is to create an inverse relationship between the antenna elements; thickness and their length. For a very fine wire antenna, an approach to the axis of the conductor leads to a rise in the magnetic field for a given current, as I/r, where r is the determination of the radial distance outwards from the conductor. Thus, the making dipole antenna from thick rods rather than thin wires is a better broad-banding method, up to a certain point. The radiation pattern then gains a maximum value in the direction pointing away from the reflector. On the contrary, the antenna structure seems to be more broadband than the simple H antenna thus it becomes much easier to construct [46]. Gain It is the division of the power density radiated in a given direction against a probable power density radiated at by a lossless isotropic radiator with a similar summation of acceptable input power. In the case of an unspecified direction, the gain value takes a meaning of the maximum value in any given direction for a specified antenna, and the antenna boresight takes meaning for the maximum directional gain. The division of the gain by the directivity yields the efficiency in any given direction. The resistive loss in the antenna structure limits the efficiency and gain, and by objects’ resistive losses which may somehow lie inside the antenna’s near field region. The IEEE standard specifically prompts exclusion to reductions arising from polarization mismatch or impedance mismatch in the total transmitted signal. The outcome is a reduction in the transmitted signal by further amounts in any particular application and a consideration in any link budget should be mandatory [23]. Efficiency The efficiency of an antenna draws a relationship between the antenna’s delivered power and the antenna’s radiated power. A high-efficiency antenna radiates away most of the antenna’s input power present. A low-efficiency antenna absorbs most of the power as antenna’s losses. The associated losses within an antenna are typically the dielectric and conduction losses. The antenna’s ratio of radiated power to the input power depicts the antenna’s efficiency. Polarization gives an expression to the orientation of an electric flux in the electromagnetic field. The emission and receiving of vertically polarized waves and the vice versa are by the vertical antenna. Polarization generally finds use when referenced to the directional electric field. The reflection of light from metal surfaces does not lead to the occurrence of polarization. So the presence of polarization translates to a similar presence of incident light in the reflected light. The angular change from the incident to the reflective light is the only effective reflection on polarization, and its absence will not bring any significant change. In a dipole antenna case, the alignment of the electric field remains so with the antenna axis as it propagates. The wave is considered to be polarized linearly with the field remaining in a particularly directed position. For practical reasons, the field’s orientation usually resolves into vertical and horizontal components. The creation of vertically and linearly polarized electromagnetic waves is by a vertical dipole antenna. The generation of the largest current due to an exposure to an electromagnetic wave takes into consideration the vertical alignment of the receiving antenna [21]. Therefore, the type of polarization and the transmitting antenna’s direction are known imperatives during the process of receiving a signal. The large and vertically oriented antennas constitute the commercial radio broadcasts. They are, therefore, linearly and vertically polarized signals that the vertical antenna offers the best receivership for the signals. Therefore, holding the antenna upright maximizes the reception of a radio signal with the only possibility into consideration not being just linear polarization. Another type, where there is the rotation of the electric field during its travel, is circular polarization. Circular polarization finds it use in satellite communications mainly because of its lack of intellectual requirement in the configuration of the satellites antennas’ orientation called skew. Faraday’s rotation is an Earth’s magnetic field causing linear polarized signals from the empty space as subjects of rotation [15]. A flat surface reflection or filtering of a sunlight wave changes it from the unpolarized state to a polarized state. The sunlight appears to be glare when reflected off the surface of a road. The horizontal polarization of the light becomes a process during its reflection. The reduction of the glare is as a result of sunglasses with vertical polarization that lead to the blockage of the component. Therefore, holding two pairs of the glasses at right angles is an easy check for polarization. In the final case, the blockage and the opaque appearance of the lens are all possible orientations of effective linear polarization. Impedance matching For very different reasons, the importance of impedance matching is in two separate instances. The instances include the match from the transmitter to the transmission line and the match from the transmission line to the antenna. The output impedance of the transmitters is of 50 ohms. In some cases, additional circuitry is contained in most modern transmitters for the limitation of the current or voltage to a reduction of the output power. So, connecting the transmitter to a 50 ohm loads ensures the harness of the most power from the transmitter. The transmitter requires more current or voltage if there is a difference in the load impedance and lack of guarantee from the manufacturer on delivery. The output from the transmitter should set the output impedance to 50 ohms with the configuration having no ties to the functionality of the antenna or its efficiency. Several techniques can effectuate the achievement of the task, including the transmitter output being synched with an antenna tuner. The technique ensures the surety in the operation of the transmitter according to its specifications and nothing more or less. The generation of full power into the line by the transmitter deprecates all the available power for use [45]. The deliverance of power from transmitter-to-antenna and antenna-to-receiver is by means of the transmission lines. When the transmission line terminates at a matching load to its characteristic impedance, the load absorbs the total power. However, if the termination of the line is at impedance not matching its impedance characteristic, then the total power is not absorbed and as a result, some of it gains a consequent reflection and fed back towards the transmitter. On arrival at the transmitter, a subsequent reflection is back again towards the load. The absorption of all the power is then eventually at the load leaving a higher current on the transmission line at the mean time surpassing the needed requirement. More losses are on the line if the load does not match the transmission line. So, in order to determine the importance of the mismatch losses, the feed line losses are a necessary determination. Parallel lines do not normally gain severe effects from mismatch or high stand wave ratio and are relative to low loss. Generally speaking, there is rarely any major benefit from the improvement of the match to parallel lines unless in the case of a very high frequency or a long line. The full power absorption by the antenna to its radiation is in effect as a result of matching the transmission line and the antenna but does not ensure maximum efficiency in the transmitter’s operations. Likewise, the match of the transmitter to the transmission line does not cause any effect to the transmission line losses mainly because its determination is by matching the transmission line to the antenna. Basic antenna models Isotropic radiator is a form of transducer used to produce useful multidirectional electromagnetic field output with equality in intensity and an efficiency of 100 percent; it finds its primary use as a reference source in standard laboratories. The dipole antenna circuitry configuration is mainly of a broken wire in the center with a connection to an insulator of each broken half for the wires’ division into two equal segments. The movement of the dipole is in all directions right angled to the antenna’s axis. The horn antenna finds use in the transmission and receivership of microwave signals and is mostly functional in feeding waveguide. The use is of a reference antenna. The horn antennas find other uses as parabolic antennas’ feeds and as gain standards. Types of coil used for transmitting power wirelessly Introduction The losses incurred during the transmission of electrical energy are a major drawback in current power distribution. The increase in demands for power leads to a consequent increase in power generation leading to power loss increase during transmission [50]. The assumption is that a third of the power generated is a waste on distribution. The pace for the development of new power technologies must keep its end of the bargain. A peak of wireless power transmission leads to effectiveness in efficiency during the transmission of electrical power between two different points. The medium of transmission being a vacuum or the atmosphere, the use of wires or other substances is, therefore, void. For the achievement of the best configuration, the efficiencies of the four different coil types in use for the coil arrays, require a comparison. The marks for the four types of coils require a definition a) The transmitter coil (TXC) The TXC is a power feeding coil. b) The repeater coil (RepC) The RepC extends the wireless power transmission distance. c) An open coil The coil is non-activated and unused. d) The nine transmitter coils (9 TXC’s) The nine coils share a single power source. a) 1 TXC scheme b) nine TXC scheme c) one TXC + eight RepC scheme +  d) Proposed stacked 1 TXC + 4 RepC scheme The above figure displays the four different coil arrays on an x-y axis shown on a piece of paper. Wireless power transmission involves the magnetic coupling of conductors whose configuration ensures that the change on the current flow on one conductor transfers voltage onto another conductor by the means of electromagnetic induction. The inductive coupling quantity between any two conductors is a determination of their mutual inductance. The application of resonance effects enhances the transmission of wireless power. The transmitter and receiver inductors tune into a mutual frequency. The power on transmission per unit distance enhances up to a 1/3 or ¼ the size of its primary coil. Both transmitting and receiving coils are single layered solenoids or flattened spirals with series capacitors whose combination allows the tuning of the receiving element to the transmission frequency. Electromagnetic induction is a function of frequency, the conductor’s current intensity, and the voltage producing the fields. The induction effect is only greater with an increasing frequency. The energy transfer is from the primary coil to the secondary coil. The coupling between two conductors increase with the coil winds and positioning them close together on a common axis. The technique enables one coil to pass its magnetic field through another coil. A higher efficiency is only achievable through tight coupling. The increase in distance between the primary and the secondary lowers coupling as some magnetic field misses the secondary. Resonance enhanced electrodynamics induction assists in battery charging for laptops and cell phones. Link efficiency A measure of the effectiveness of the electrodynamics induction relates to link efficiency, ηlink. It measures the ability of the primary and secondary coils to transfer energy between each other. ……………….6 link efficiency Where: K = Magnetic coupling factor ……………………………………………………………………7 = unloaded quality factor of the primary circuit ……………………………………………………………………8 = unloaded quality factor of the secondary circuit ………………………………………………………….……...9 Where: QE = Effective Q RE = the effective load resistance that models the rectifier with an inclusion to the output filter capacitor and actual load resistance RL. The relationship between RL and RE is ……………………………………………………………..10 If series resonance is in use on the secondary side, W = primary angular velocity (2πf) W2 = secondary angular velocity (2πf2) L1 = primary inductance in Henries r1 = primary dc resistance in ohms L2 = secondary inductance in Henries r2 = secondary dc resistance in ohms The loaded quality factor is: ………… for the efficiency to have a maximum value, the link to the secondary resonance frequency requires a tune. The effective load resistance sets to: ………………………………..11 To maximize KQ; the figure of merit: …………………………………………………………………12 Q is the system quality factor, and its increase will enhance the compensation ability of the low magnetic coupling affair. Optimum efficiency, therefore, …………………………………………..…….13 The figure below shows a plot of the optimum link efficiency, ηopt, against the figure of merits, KQ, for the coils. The management of a higher value of K is the use of ferromagnetic shield (core) to enhance the magnetic coupling factor with the reduction of the stray magnetic field. The maximization of the quality factor, Q, for the inductive coils is other means of managing high-efficiency inductive solution. The reduction in the vertical distance between coils and the vertical alignment of the same coils improves the magnetic coupling factor, K. Figure 8. Optimum link efficiency Evaluating the electromagnetic induction method The basic approach behind the wireless power transfer is the magnetic induction between the transmitting and receiving coil. The excitation of the transmitter coil generates some flux leading to the development of potential difference across the terminals of the receiver coil. The developed potential difference directly relates to the distance between the transmitter and receiver coil. Due to poor efficiency of the basic model of WPT, the technique is not effective for large distance transmission. Figure 9 WPT For the model to be effective for the transmission of power through long distances, intermediate coils require an introduction between the transmitter and receiver coil. The intermediate coils are now the repeater coils whose main use is to amplify the transmission of the power signal between the transmitter and receiver coils. Figure 10 WPT and image The efficiency of the transmission gains an increase due to these repeaters. The spiral coil demonstration on Fig. five also configures transmitters and receivers leading to an improvement in the efficiency. Various coil shapes The validity of introducing extra coils needs many more resonant coils and an adjustment to the location of the extra coils. The effect of various coil shapes then needs a consideration. A 3D electromagnetic moment method calculation package (WIPL-D), resolves the complex shapes problem. The numeric code WIPL-D calculates the transmission efficiency up to a meter for the various shape coils. The technique works for the spiral coil and the square and circular loop coils with the resonant coil being 0.1 [m] for the longest side of each coil. The resonant frequency for each coil requires an adjustment to around 22MHz with the equipment of a suitable capacitor. In the spiral coil case, the transmission distance is over a meter for HEMS conditions. The reason is that the transmission efficiency needs to be larger than 0.13%. Various size coils The idea is that using a larger transmitting coil in comparison to the receiving coil reduces the magnetic flux divergence at a further distance between the coils. The concluded observation is a model of a transmitting coil (1m diameter) ten times larger than the original one. The model harmonizes perfectly with HEMS because the location of the receiving coil is less than 2 m from the floor, and the larger transmitting coil is the only one that mounts on the floor. WIPL-D calculates the result. Wireless power transmission regards as the most important technology for the supply of consumption power wirelessly into other senior network nodes. A consideration on the coil shapes and arrangements while using resonance type wireless power transmission is mandatory. An extra consideration on the various coil size (10 times), shape coils, and the way of the repeating coil is critical to the evaluation. Application note The success of the wireless power transmission solutions depends on the standard compatible protocols on the transmitter and receiver sides and how they adhere to the regulations. The technology becomes popular regardless to the manufacture once the certainty of charging the devices at any compatible station approves. Hence, critical understanding and evaluating the standard protocols that are present in the market and the technology behind their existence mandated. Close – coupled Qi Standard Wireless Power Consortium (WPC) WPC deals with the transmission of energy by the means of inductive coupling over short millimeter range distances. The transmitter (TX) coil and the receiver (RX) coil couple through a magnetic field. The magnetic field concentrated within a small area in between the transmitter coil and a receiver coil. The supply of energy is only certain from a single transmitter to a single receiver at a time. The frequency range is between 100 kHz and 205 kHz. Wire wound on ferrite or printed traces on the circuit board are factors for the coil shapes. The Qi solution establishment in the market consists of an estimate of more than 230 devices on approval. The sales of the devices approximate to 16 million units within the universe. Loosely-coupled (LC) Wireless Power Transfer (Magnetic Resonance) the Alliance in the Wireless Power Transmission The frequency of the transmitting coil and the receiving coil are at a resonance during the supply of energy. The tune of the receiver to the resonant frequency ensures efficiency of the received energy. The phenomenon is magnetic resonance and works at large distances in the z-direction to an estimate of 50 millimeters. The receiver has no precise positioning as its placement is not critical. A single transmitter can transmit energy to multiple receivers at the same time. Current power classes are up to 22 W for smartphones and tablets. The frequency range of 6.78 MHz (ISM band) is for charging energy and 2.4 GHz (LP Bluetooth) for data. Data delivery also requires a frequency range of 2.4 GHz (LP Bluetooth). There are no current standards passed for neither LC nor commercial products on arrival in the market. Power Matter Alliance (PMA) PMA offers a similar solution to WPC on short distance inductive coupling phenomenon. Compatibility of both PMA and WPC devices such as smart phones is the same to some chargers and charger adapters, but this should not speculate an assumption of exactness in the technology used. The PMA solution is in use of a different protocol and transmission frequency bandwidth from WPC. The characteristics such as the frequency range and protocol availability are only PMA members. There is an absence of direct compatibility with A4WP or WPC. Some semiconductor manufacturers such as Texas Instruments attempt to offer chipset solutions to the possibility of working with both WPC (Qi) and PMA standards. The chipsets have a recognizable ability on the type of coils and transceivers that are nearby. On either the side of the transmitter or receiver, and have an adjustment for the transmission of energy in either the Qi or PMA frequencies.The standards on WPT are presently on the drive by the consumer market with limits to solutions on a standard 20 W. WPC proposes solutions are trending to 2.4 kW for wireless kitchen appliances and other applications. The definition of 200 W, 800 W, and 2.4 kW proposed classes will create a wide range of application solutions in consumer, medical and industrial markets. The main application areas are large battery charging and power supply for industrial equipment. The Qi system The schematic consists of a transmitter that supplies 5 W to the receiver coil. A specific power management protocol implements the communication between the transmitter and receiver. An operating frequency at the range of 100-205 kHz delivers the power between the coils. The transmitter adjusts to the receiver’s request of energy in requisition. The power management system monitors and adapts to the energy transmission. The system schemes to a standby mode when the receiver is not in need of additional energy. The achievement of low power transmission losses requires crucial characteristic analysis of the transmitter and receiver coils. The requirement includes proper selection and positioning for the transmitter and receiver coils to influence the efficiency on the energy transmission. Key factors for the coils A series of factors describe the best possibilities to curb and minimize energy losses during transmission. Placement of the coils: Proper alignments of the transmitter and receiver coils helps to succintly minimize losses. Vertical, centered and lateral misalignments are detrimental considering energy transmission. The size of the effective area of the receiver coil in the transmitter’s magnetic field speculates good coupling and the transmission of maximum energy. Moreover, the distance in the z-direction is also dependant. The transmission losses are more likely to be minimal by the centering of the receiver coil with the transmitter coil without casting with a low as possible distance in the z direction. If the coupling factor is 1, then it is ideal. Coupling: the design of coils with high coupling and quality factor compensates for the misalignment losses. The parameters for the coupling factor between the transmission coil and a receiver coil consists of the formula: ……………………………………………………………14 The coils’ self-inductances consideration for the L1 and L2. With regards to the mutual inductance between the two coils is M. the resistance loss RL and the reactance XL are dependants on the quality factor of the coils. ………………………………………………………………………...15 A typical quality factor ranging between 100 and 300 is in the air coils with ferrite plates. The various factors influence the ohmic resistance of the wire and also the resistance of the coils. Skin effect: the term refers to the displacement of an electric current from the center of the wire towards its surface. The phenomenon is in conductors carrying alternating current. Its dependency is on the frequency of the alternating current such that an increase in the alternating current frequency causes a subsequent increase on the current’s concentration on the conductor’s surface. Therefore, the majority of the currents to the surface are on displacement by the high frequency alternating current. Thus, the current density is lower on the center of the conductor than on its surface. A description of the penetration depth δ gives: ………………………………………………………………………………………..16 ρ specific resistance ω angular frequency µ sheared effective permeability (e.g.: 100) The measure of the penetration depth measured as the outer diameter towards the center of the conductor. The skin effect leads to a reduction in the area of flow of current and as a consequence the resistance on this small area rises. A higher resistance leads to high energy losses. The significant reduction of energy losses from the skin effect is achievable by the use of high-frequency wire strands in the transmitter and receiver coils. Thin wires braided in a group of two or more wires is a characteristic feature of a high-frequency wire. The individual wires in the group carry a proportion of the total current. More energy is then ineffective use due to minimized skin effect. Proximity effect: the factor causes constriction or the displacement of current in closely spaced conductors. The consequent result is due to the magnetic flux leakage in each conductor. The reduction of eddy currents in the coils is achievable by the analysis of the structure of wire insulation, winding technology and wire strand configuration. Loss factor: the limit of the wireless energy transmission in the system is by the loss factor. The definition of the loss factor λ is: ………………………………………………………………..17 ……………………………………………………………………18 The ratio expresses the total energy loss to the energy quantity transmitted. The main goal is the achievement of minimal loss factor in the system. The optimization in the configuration of the transmitter and receiver coil achieves the minimal loss factor. However, the coupling factor and the quality factor still inherently affect the loss factor of the system as a whole. …………………………………………….…..19 Figure 16. Product of the coupling factor and the quality factor The equation above shows how the product of the coupling factor and the quality factor get a consideration of the figure of merit (FOM). The compensation for the deteriorating loss factor as a result of poor coupling factor is considered and amassed from the quality factors of individual coils. Field pattern: the magnetic element influences the coils efficiency. Read More