https://www.wirelesspowerwiki.com/ 2026-04-10T09:18:39+00:00 https://www.wirelesspowerwiki.com/ https://www.wirelesspowerwiki.com/lib/exe/fetch.php?media=wiki:logo.png text/html 2025-05-01T14:08:22+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=abbreviations&rev=1746108502&do=diff Abbreviations CPT: Capacitive wireless power transfer IPT: Inductive wireless power transfer WPT: Wireless power transfer FOD: Foreign object detection BPP: Baseline power profile EPP: Extended power profile MPP: Magnetic power profile Tx: Transmitter text/html 2025-05-29T13:48:55+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=acoustic_wireless_power_transfer&rev=1748526535&do=diff Acoustic wireless power transfer Acoustic Power Transfer (APT) is a wireless power transmission technology that uses sound waves, typically in the ultrasonic frequency range (above 20 kHz), to deliver energy over a physical medium such as air, water or solids. Unlike electromagnetic wireless power systems, APT is not affected by EMI and is especially useful for applications in biomedical implants, underwater systems, and metal-enclosed environments. Not only can APT be used to power systems, i… text/html 2025-12-27T16:05:59+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=admittance_inverter&rev=1766851559&do=diff Admittance inverter Definition An admittance inverter changes an output admittance $Y_{out}$ to its inversely proportional value $Y_{in}$, multiplied by a value J²: $$Y_{in}=\frac{J^2}{Y_{out}}$$ J is a susceptance (in siemens), and is called the characteristic admittance of the inverter. For the ABCD matrix of an admittance inverter, it holds that A=0 and D=0, with the ABCD matrix of a two-port network defined as: $$\begin{bmatrix} V_1 \\ I_1 \end{bmatrix} =\begin{bmatrix} A & B\\ C & D \e… text/html 2025-05-01T12:52:04+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=bidirectional_in-band_communication_in_the_qi_standard&rev=1746103924&do=diff Bidirectional in-band communication in the Qi standard In-band communication The latest version of the Qi standard, designated as Qi2, facilitates power transfer of up to 15W through Magnetic Power Profile (MPP). This wireless energy transmission occurs via inductive close coupling between transmitter and receiver coils, utilizing a time-varying magnetic field as the transfer medium. The operational frequency spectrum for establishing effective power transfer typically ranges from 100 to 200 k… text/html 2025-06-04T16:06:08+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=capacitive_wireless_power_transfer&rev=1749053168&do=diff Capacitive Power Transfer Capacitive Power Transfer (CPT) works by using electric fields to transfer energy between two sets of electrodes separated by a dielectric material, for example air. When a high frequency alternating current signal is applied to the transmitter electrodes, it generates a varying electric field across the dielectric medium. This electric field induces a displacement current between the electrodes, allowing energy to be transferred from the transmitter side to the receiv… text/html 2025-06-09T12:19:37+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=compensation_networks&rev=1749471577&do=diff CPT compensation networks The coupling coefficient for a CPT system tends to be of lower value because of the limited size of the capacitive plates and the low permittivity of air. This will result that the coupling impedance in general is way higher than the load impedance, negatively influencing the efficiency because of the voltage drop over the coupling. To overcome this, compensation networks are used. These networks increase the voltage on the transmitting side and decrease it on the rece… text/html 2025-06-22T14:47:28+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=coupling_coefficient&rev=1750603648&do=diff Modification of the Coupling Coefficient To see the effect of changing coupling coefficient, k will be altered while the other parameters stay constant. The following code is used in LTspice: .step param k list 0.1 0.2671 0.40 0.55 0.70 0.85 1 This will overlay simulation results while sweeping the k parameter from 0.1 to 1. Changing k in the physical setup can be done by changing the distance between the coils, changing the alignment of the coils or changing the size/shape of the coils. Bel… text/html 2025-06-04T16:34:48+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=cpt_structures&rev=1749054888&do=diff Type of CPT structures There are different types of CPT structures. The first to be discussed is the two-plate structure, shown in the figure below. Like the name states, only two capacitive plates are used to transfer the power. Two-plate CPT can be divided into three types: (a) two-plate for EV’s, (b) two-plate for single wire application, and text/html 2025-03-28T14:06:51+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=different_power_gains&rev=1743170811&do=diff Different Power Gains Types of power gain If you hear the word 'power gain', you justly interpret this as the ratio of the output power $P_{out}$ to the input power $P_{in}$: $$ gain=\frac{P_{out}}{P_{in}}$$ Unfortunately, confusion is possible, since there are different ways to define the ouput and input power. And depending on which definition of power you use, you get another value for the gain. But mankind has found a solution: we use different names for the gains, depending on which pow… text/html 2024-09-10T11:51:59+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=done&rev=1725969119&do=diff Done Overview of finished pages. However, don't hesitate to edit (in particular when you find a mistake)! * Evolution of the numbers of papers on wireless power transfer * The advantages and disadvantages of wireless power transfer * Abbreviations * Simulating a time-varying resistor in Spice * Different Power Gains * Simulating a time-varying inductor in Spice * Simulating a time-varying capacitor in Spice text/html 2025-06-26T06:38:07+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=drafts&rev=1750919887&do=diff Drafts These pages are in construction: * Frequency of WPT * Partity-time symmetric WPT text/html 2024-05-31T15:59:53+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=evolution_of_the_numbers_of_papers_on_wireless_power_transfer&rev=1717171193&do=diff Evolution of the numbers of papers on wireless power transfer Let's us look at the timeline of the number of papers (journal and conference papers) published on wireless power related topics. We limit ourselves to Scopus because we are not trying to do a rigorous study, we just want to get a general idea. text/html 2025-05-01T14:17:46+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=foreign_object_detection_in_the_qi_standard&rev=1746109066&do=diff Foreign Object Detection in the Qi standard Classification of FOD methods In the Qi standard, the transmitter emits power to the receiver via an high-frequency alternating magnetic field. Qi technology is defined as a low-power transfer standard which implies that it poses no health risk to living objects (LOs). In the Qi standard, no living object detection (LOD) is performed as there is no space between the charging pads where LOs (e.g. animals) can enter and interfere with the WPT. However,… text/html 2025-03-30T06:26:00+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=frequency_of_wpt&rev=1743315960&do=diff Frequency of WPT WPT must be high frequency in order to achieve high efficiencies. Typically, the range of a few kHz to MHz is used for near-field WPT technologies as inductive and capacitive WPT. For radiative WPT, frequencies higher than GHz are typical. text/html 2025-05-04T07:46:48+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=immittance_inverter&rev=1746344808&do=diff Immittance inverter An immittance inverter is the collective name for impedance and admittance inverters. We refer to the following pages for more details: * Impedance inverter * Admittance inverter text/html 2025-12-27T16:06:10+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=impedance_inverter&rev=1766851570&do=diff Impedance inverter Definition An impedance inverter changes an output impedance $Z_{out}$ to its inversely proportional value $Z_{in}$, multiplied by a value K²: $$Z_{in}=\frac{K^2}{Z_{out}}$$ K is a reactance (in ohm), and is called the characteristic impedance of the inverter. For the ABCD matrix of an impedance inverter, it holds that A=0 and D=0, with the ABCD matrix of a two-port network defined as: $$\begin{bmatrix} V_1 \\ I_1 \end{bmatrix} =\begin{bmatrix} A & B\\ C & D \end{bmatrix}… text/html 2024-04-05T06:54:10+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=inductive_wireless_power_transfer&rev=1712300050&do=diff $$ \frac{d}{dx}\left( \int_{0}^{x} f(u)\,du\right)=f(x) $$ $a^2 + b^2 = c^2$ resonancefrequency IPT resonance frequency text/html 2025-05-01T07:31:01+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=introduction_of_the_qi_standard&rev=1746084661&do=diff Introduction of the Qi standard What is Qi The Qi (pronounced chee) standard is a inductive power transfer (IPT) technology. The standard is developed for smartphones and other mobile devices. Therefore, Qi is considered a low-power and static WPT charging standard. Transmitter and receiver are placed in text/html 2024-04-05T21:09:20+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=ipt_resonance_frequency&rev=1712351360&do=diff Resonance frequency of coupled coils Circuit We consider two coils with inductances $L_1$ and $L_2$, coupled by mutual inducance $M$. In series, capacitors $C_1$ and $C_2$ are added to the circuit. The resistive losses of the circuit are represented by the resistances $R_1$ and $R_2$\begin{align} Z = \begin{bmatrix} z_{11} & z_{12} \\ z_{21} & z_{22} \\ \end{bmatrix}= \begin{bmatrix} R_1+j\omega L_1+\frac{1}{j \omega C_1} & j \omega M \\ j \omega M & R_2+j\omega L_2 +\fr… text/html 2025-06-22T14:39:22+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=ipt_simulation&rev=1750603162&do=diff LTspice IPT simulation Below fogure shows a LTspice schematic of a SS IPT system. To mimic the source, the pulse function is used. This will give a bipolar square wave with a frequency of 20 kHz. When the simulation was originally run, there was a slight difference between the simulated results and the reported results. This is because LTspice does not automatically takes ESR, copper losses, etc into account. Below figure and tablev how the simulated results rounded to two decimals. The roun… text/html 2025-06-09T12:42:25+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=ipt&rev=1749472945&do=diff Inductive Power Transfer The basic principle of inductive coupling or inductive power transfer (IPT) is the wireless transfer of power through a medium using magnetic fields generated by inductive coils. It is based on the principle of Ampère’s circuital law, which describes the creation of a magnetic field in a wire where current is flowing and Faraday’s law of induction, which describes the induced current in a wire due to a magnetic field.$$ k = \frac{M}{\sqrt{L_1 L_2}} $$$$ \eta = \frac{k^2… text/html 2025-06-09T11:55:15+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=laser_power_transfer&rev=1749470115&do=diff Laser Power Transfer LPT uses a focused, coherent beam of light towards a distant PV receiver that converts that light into electricity. It consists of three main subsystems: * The laser emission subsystem * Ordered List ItemTransmission * text/html 2025-06-22T15:51:43+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=load&rev=1750607503&do=diff Modificaton of the load To see the effect of a changing load while all other parameters are constant, the following code is used in LTspice: .param RL = 5 Rload n2 0 {RL} .step param RL list 2 5 10 20 50 100 This will overlay the results while the load changes on each step. The table below shows the simulated results. Because only RL changes and all other parameters remain constant, this analysis also captures the system’s behaviour when changing the quality factor of the receiving side. text/html 2025-06-22T14:10:52+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=ltspice_manual&rev=1750601452&do=diff LTspice Manual After the installation process, the software is ready to be used. When the program is launched, the following startup screen is displayed. From this screen, the following actions can be performed: * Adjusting the program settings text/html 2025-06-22T16:10:58+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=ltspice_simulations&rev=1750608658&do=diff LTspice Simulations To explore and test different WPT systems, companies can use simulation tools like LTspice. This chapter provides a short introduction to the software and includes a few example simulations to show how it can be used for designing and analysing WPT circuits. For the full potential of the software, a small manual is made in the chapter: text/html 2025-06-01T20:55:40+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=microwave_rf_wireless_power_transfer&rev=1748811340&do=diff Microwave/RF wireless power transfer Microwave or Radio-Frequency (RF) wireless power transfer uses high-frequency electromagnetic (EM) waves in the range of 300 MHz to 300 GHz to wirelessly transfer energy between a transmitter and a receiver. It can operate both on the near- and far-field depending on the distance and frequency. RF WPT generates RF energy at a transmitter, radiating it through space and capturing it at a receiver where it is converted back into usable DC power. The transition… text/html 2025-04-30T15:16:27+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=overview_of_wireless_power_transfer&rev=1746026187&do=diff Overview of wireless power transfer Overview Wireless Power Transfer (WPT) can be implemented in many ways. The most well-known technologies in the sector today are depicted in Figure 1 and can be divided into WPT by acoustic or by electromagnetic means text/html 2025-07-07T14:27:51+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=partity-time_symmetric_wpt&rev=1751898471&do=diff Parity-time symmetric WPT PT symmetry One of the main challenges of near-field WPT, in particulary IPT, is the sensitivity of the system towards changes in distance between transmitter and receiver, misalignment, load variation and changes in frequency. As a result, practial WPT systems often experience unstable behaviour. $x$$-x$$L_1$$L_2$$t$$-t$$R_1$$R_2$$R_L$$-R_N$$V_1 (I_1)$$V_2 (I_2)$$-R_N$$R_L$$$\begin{bmatrix} R_1+j(\omega L_1-\frac{1}{\omega C_1}) & j\omega L_{12}\\ j\omega L_{12} & R_… text/html 2025-05-01T14:11:27+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=power_transfer_architecture_of_the_qi_standard&rev=1746108687&do=diff Power Transfer Architecture of the Qi Standard The transmitter (Tx) and receiver (Rx) go through an advanced process for power to be transferred. This process comprises four phases in the baseline power profile (BPP), namely the selection, ping, identification & configuration, and power transfer phase. In the text/html 2025-06-22T15:58:45+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=quality_factor&rev=1750607925&do=diff Modification of the quality factor In this chapter, the modification of the quality factor of the primary circuit will be analysed. To analyse this, a loss resistance Rloss is added in the primary circuit and will be modified while the other parameters remain constant. Changing Rloss will change Q1. Following code is used to change the value of Rloss: text/html 2025-06-02T19:41:54+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=rayleigh_distance&rev=1748893314&do=diff The transmitting distance can be divided into three distinct zones, based on the distance from the source and the behaviour of the acoustic wave. (Reactive) Near-field zone The near-field or also called the reactive zone lies very close to the surface of the transmitting transducer, typically within one wavelength. In this region, the acoustic pressure and particle velocity are not in phase and standing wave effects dominate. This means that the acoustic energy is mostly stored and not radiat… text/html 2025-06-22T16:08:37+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=resonant_frequency&rev=1750608517&do=diff Modification of the frequency To see the effect of changing the resonant frequency, two separate analyses are conducted: * Changing the frequency while maintaining the other parameters. * Changing the frequency while maintaining resonance by simultaneously adjusting the capacitors. text/html 2025-06-09T13:07:39+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=shielding_techniques&rev=1749474459&do=diff Shielding techniques of an IPT system Shielding plays a crucial role in improving the power transfer efficiency, limiting EMI and protection nearby electronic devices from inducing currents. There are three common methods used: * Ferrite shielding text/html 2024-09-10T11:51:35+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=simulating_a_time-varying_capacitor_in_spice&rev=1725969095&do=diff Simulating a time-varying capacitor in Spice The relationship between the voltage $v_C$ over and the current $i_C$ through a capacitor is determined by its capacitance $C$: $$ i_C(t)=C\frac{dv_C(t)}{dt}$$ However, this current-voltage relationship is not valid when the capacitor is varying in time. For a time variant capacitor, the equation modifies to:$$ i_C(t)=\frac{d}{dt}[C(t).v_C(t)]=C(t)\frac{dv_C(t)}{dt}+v_C(t)\frac{dC(t)}{dt}$$$$ v_C(t)=\frac{1}{C(t)}[C(0)v_C(0)+\int_0^t i_C(t) dt] $$$… text/html 2024-09-10T09:01:20+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=simulating_a_time-varying_inductor_in_spice&rev=1725958880&do=diff Simulating a time-varying inductor in Spice The relationship between the voltage $v_L$ over and the current $i_L$ through an inductor is determined by its inductance $L$: $$ v_L(t)=L\frac{di_L(t)}{dt}$$ However, this current-voltage relationship is not valid when the inductor is varying in time. For a time variant inductor, the equation modifies to:$$ v_L(t)=\frac{d}{dt}[L(t).i_L(t)]=L(t)\frac{di_L(t)}{dt}+i_L(t)\frac{dL(t)}{dt}$$$$ i_L(t)=\frac{1}{L(t)}[L(0)i_L(0)+\int_0^t v_L(t) dt] $$$L(t)… text/html 2024-09-06T19:21:20+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=simulating_a_time-varying_resistor_in_spice&rev=1725650480&do=diff Simulating a time-varying resistor in Spice Suppose we want we simulate a time-varying resistor, e.g., a sinusoidal value in function of time with a certain offset: R1(t)= 5 Ω + 3 Ω.sin(2π.10.t). This can be realized by introducing an independent voltage source with voltage equal to the requested value of the resistor, i.e. 1 V corresponds to 1 Ω. Thus for our example, we need to introduce a voltage source with DC offset 5V, amplitude 3V and frequency 10 Hz. We allocate a label to the output o… text/html 2025-06-21T13:40:31+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=start&rev=1750513231&do=diff * Evolution of the numbers of papers on wireless power transfer * The advantages and disadvantages of wireless power transfer * Abbreviations * Simulating a time-varying resistor in Spice * Different Power Gains * Immittance inverter * Impedance inverter * Admittance inverter * Overview of wireless power transfer * Introduction of the Qi standard * Power transfer architecture of the Qi standard * Bidirectional in-band communication in the Qi standard * Foreign object det… text/html 2025-02-26T14:41:36+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=the_advantages_and_disadvantages_of_wireless_power_transfer&rev=1740580896&do=diff The advantages and disadvantages of wireless power transfer The advantages Wireless power transfer (WPT) has several advantages compared to wired charging: * The most important advantage, certainly for portable electronics, is the improved convenience and user experience text/html 2025-06-09T11:53:06+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=transmitting_distance_for_acoustic_and_rf_based_wpt&rev=1749469986&do=diff The transmitting distance can be divided into three distinct zones, based on the distance from the source and the behaviour of the acoustic wave. (Reactive) Near-field zone The near-field or also called the reactive zone lies very close to the surface of the transmitting transducer, typically within one wavelength. In this region, the acoustic pressure and particle velocity are not in phase and standing wave effects dominate. This means that the acoustic energy is mostly stored and not radi… text/html 2025-06-09T12:50:26+00:00 Anonymous (anonymous@undisclosed.example.com) https://www.wirelesspowerwiki.com/doku.php?id=type_of_coils&rev=1749473426&do=diff Type of coils in an IPT system The type of coils used in an IPT system can influence the performance of an IPT system. It is therefore important to consider different key aspects when designing a coil for the IPT system. The mutual inductance, self-inductance, coupling coefficient, and misalignment variation are among the key factors that are affected by the coil geometry designs. This also includes the number of turns in the coil, the number of turns and the pitch. Another important factor is …