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High signal to noise ratio (SNR) in magnetic resonance imaging is vital for ensuring accurate diagnosis and treatment. Arrays of surface coils for receive only purposes is a well established way to increase SNR. However, due to crosstalk between the array elements, the SNR can be severely degraded. For that reason, arrays often do not exploit their full potential. By using a series decoupling network...
High signal to noise ratio (SNR) in magnetic resonance imaging is vital for ensuring accurate diagnosis and treatment. Arrays of surface coils for receive only purposes is a well established way to increase SNR. However, due to crosstalk between the array elements, the SNR can be severely degraded. For that reason, arrays often do not exploit their full potential. By using a series decoupling network...
This paper proposes spread spectrum methods to reduce radiation noise caused by an inductive power transfer (IPT) system. A noise reduction method with spread spectrum techniques has been proposed. The proposed noise reduction method randomly changes the output frequency of an inverter within a range of 79-to-90 kHz. Changing the output frequency, the radiation noise is spread in a frequency domain...
A maximum power point (MPP) tracking technique for electromagnetic energy harvesters is presented. The concept is based on using a bidirectional AC/DC converter to simultaneously counteract the effect of the output inductance and match the output resistance of the harvester, in order to perform maximum power transfer. The modulating signal for the AC/DC converter is generated by sensing and processing...
Omnidirectional wireless power transfer (WPT) system has been studied recently due to its better user experience compared with directional WPT system. And this paper focus on resonant converter topologies study in omnidirectional WPT system. At first, three challenges of resonant converter design are identified: I. moving resonant frequency under variable coupling condition; II. voltage controllability...
In order to achieve high efficiency, IPT systems must work under resonance conditions. Since, the coupling coefficient is low (k<0.5) compared to a transformer, the compensation is done separately in the primary and the secondary sides. However, depending on the system, both systems can alter each other, creating pole-splitting or bifurcations. This paper presents a design criterion to ensure that...
Wireless power transfer (WPT) via magnetic resonance coupling has gathered attentions because of its high transmitting efficiency and robustness to misalignment. The efficiency characteristics of the WPT system are expressed by kQ product, which is given by coupling coefficient and quality factors of a transmitter and receiver. However, a conventional measuring method of the kQ product is quite burdensome...
The output power of a magnetic resonant coupling wireless power transfer (WPT) system drastically decreases when the distance of couplings coils changes due to impedance mismatch. A maximum power point occurs at only one optimal distance. These characteristics are caused by limitation in design stage. This paper proposes a new impedance tuning method of tracking, for maximum power point, by adjusting...
In this paper, we analyze the refraction of magneto-inductive waves by surrounding metallic loops in underwater sensor networks. Previous work proposed positive and negative refraction of magneto-inductive waves. Here, we discuss properties of different structures of the placement of coils with the aid of the dispersion equation and compare the performance of lattice and honeycomb structures with...
There is a conflict between the energy transfer efficiency and maximum transferred power in conventional inductive power transfer (IPT) systems, and the energy transfer efficiency is only 50% when maximum power is transferred. To solve this problem, a new topology which is operated at switched-mode is proposed in this paper. The high frequency current of the topology is generated by the free oscillation...
A novel single-wire power transmission system (SWPT) was introduced in this paper. This system consists of the transmitter and the receiver which are connected via only single-wire. The Tesla's transformer is used in both the transmitter and the receiver. The electric energy was transmitted through the spatial electric field between the transmitter and the receiver. In this paper, the lumped-parameter...
An efficient near-field RFID reader, delivering power to and receiving data from Brain-Machine Interface implants, is realized in 65 nm CMOS. A modified Class E/Fodd Power Amplifier with a current-sense resistor differentially drives a single segmented antenna, and acts simultaneously as TX and RX. It operates at 309 MHz and has 54% efficiency. The backscattered data is recovered from the current-sense...
In this article, a surface mounted device (SMD) common-mode choke (CMC) required for unshielded-twisted-pair automotive communication systems (like 100Base-T1) is characterized in detail regarding its high-frequency filtering characteristics. Firstly, the S-parameters and mixed-mode S-parameters of the mentioned choke were measured using a 4-port vector network analyzer in a frequency range of 1 MHz...
This paper presents a comparison of two structural coils (solenoid and planar spiral coil) for wireless power transfer (WPT) system in many ways. The impedance properties of two structural magnetic coils are discussed. And the influences of structural parameters (such as diameter, number of turns and layers) on the transfer performance are also analyzed. Furthermore, the magnetic resonance coupling...
To transfer large power in inductively coupled power transfer (ICPT) system, parallel secondary pickups are adopted. Because of the error of installation and measure, the parameters of parallel pickup modules are not completely consistent, resulting in the current unbalance or even over- current in parallel modules, which will damage the elements like resonant capacitance, even destabilize the system...
This paper presents a novel method to model the steady state behaviour of internal faults in transformers. Transformer with turn-to-ground fault can be represented by an impedance matrix. Modified Nodal Analysis (MNA) is employed to calculate the steady state values of node voltages and branch currents under faulted condition. The computations are implemented using a MATLAB program. Similar conditions...
This paper presents the design and implementation of an impedance compression network (ICN) to correct distance variation or misalignment between coils in wireless power transfer (WPT) systems. Magnetic resonant coupling (MRC) coils provide high efficiency for charging mid-range WPT applications. However, a distance variation or misalignment between coils causes a coil-impedance change and significantly...
Distance and frequency variation are the main causes for dramatic decrease of the output power and efficiency in wireless power transfer system. The influence of these parameters should be considered from the design stage. This paper investigates the effect of distance and proposes a method to estimate the distance with maximum output power for air-core coils. The effect of operating frequency focused...
This paper presents a design procedure of a Class E2 DC-DC converter for megahertz wireless power transfer. The design formulas are analytically derived based on the input impedance of the Class E rectifier. A 6.78 MHz Class E2 DC-DC converter is designed and implemented by means of those formulas. The power-level of the converter is 15W. The experiments are provided to verify the proposed design...
The wireless power transfer systems (WPTS) work at frequencies between 20 kHz – 40 MHz. Considering the system consisting of two magnetically coupled coils, used in WPTSs, as a passive linear two-port network (PL2PN) in harmonic state, this paper describes the possibility of using the scattering parameters S in generating the power gains between the two ports of these coils. The amplification (or...
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