Resistor-free and one-board-fits-all ratio adjustable power splitter for add-on RF shimming in high field MRI

Zhu, Y.S.; Lü, Ming; Yan, Xinqiang

doi:10.1016/j.jmr.2022.107194

Cited by 4 publications

(3 citation statements)

References 37 publications

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“…The attenuation is determined by the phase difference of the transmission lines. Several recent designs by the same group [65][66][67], including the ratio-adjustable power splitter (RAPS), achieves the amplitude weight adjusting through a specially designed power splitter alone, avoiding a dedicated attenuator and the associated power loss.…”

Section: ) High Power Phase Shifters and Attenuatorsmentioning

confidence: 99%

A Review of Current Control and Decoupling Methods for MRI Transmit Arrays

Cui,

Hollingsworth,

Wright

2024

IEEE Rev. Biomed. Eng.

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The shortened radio frequency wavelength in high field MRI makes it challenging to create a uniform excitation pattern over a large field of view, or to achieve satisfactory transmission efficiency at a local area. Transmit arrays are one tool that can be used to create a desired excitation pattern. To be effective, it is important to be able to control the current amplitude and phase at the array elements. The control of the current may get complicated by the coil coupling in many applications. Various methods have been proposed to achieve current control, either in the presence of coupling, or by effectively decouple the array elements. These methods are applied in different subsystems in the RF transmission chain: coil; coil-amplifier interface; amplifier, etc. In this review paper, we provide an overview of the various approaches and aspects of transmit current control and decoupling.

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Section: ) High Power Phase Shifters and Attenuatorsmentioning

confidence: 99%

A Review of Current Control and Decoupling Methods for MRI Transmit Arrays

Cui,

Hollingsworth,

Wright

2024

IEEE Rev. Biomed. Eng.

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“…As shown in figure 1(a), the ME laminate composite, operating in longitudinal-transverse (L-T) mode, was fabricated by size-tailored piezoelectric ceramic of PZT sandwiched by two spinel ferrites of Ni 0.8 Zn 0.2 Fe 2 O 4 (NZFO) platelets. For Cartesian coordinate system construction, the origin of the system was centered in the tri-layered ME composite with a total length of L. The arrows represent longitudinally magnetized directions of NZFO platelet and transversely polarized directions of segmented PZT slab, (1,2) in the Cartesian coordinate system are defined as the longitudinal and width directions of the sample, and direction 3 is perpendicular to the electrode plane of PZT. When the sample was subjected to an AC magnetic field of H along its longitudinal direction, the ferrite generated a periodic vibration resulting in a mediated strain to the PZT layer.…”

Section: Theorymentioning

confidence: 99%

“…Power-dividing technologies have drawn enormous attention in the research community for the last decades due to their extensive applications in microwave electronic devices, network power amplifiers, radio frequency (RF) circuits, feedback network and beam-forming antenna arrays, and electronic measurement systems, etc [1][2][3][4][5]. From a historical account, in 1960 Ernest J Wilkinson conjectured a powersplitting device prototype that divides a source signal into n paths with equiphase equiamplitude to realize efficient power combination/division while it maintains high isolation [6].…”

Section: Introductionmentioning

confidence: 99%

Arbitrary low-frequency power-splitting strategy in ferrite/piezoelectric magnetoelectric heterostructures: theory and experimental validation

Zhang,

Gao,

Filippov

et al. 2024

Smart Mater. Struct.

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Exploring low-frequency (LF) arbitrary power-splitting technologies to address the independent excitation issues of LF/VLF mechanical antennas (MA) with random distributions is challenging due to unidentified device construction and operation mechanism. In light of this, a device construction strategy for three-port magnetoelectric (ME) arbitrary power splitter in composite of ferrite/piezoelectric heterostructure, as well as theoretical model was developed. To validate the feasibility and effectiveness of the strategy, three size-tailored ME samples with length ratio of split PZT segments in 1:1, 2:1, and 3:2 were modeled, fabricated and comparatively characterized. Experimental results show that the achievable maximum power conversion efficiencies (PE) reach 52%, 71%, and 59% for three tailored ME samples, respectively, and as expected the power-splitting ratios are directly proportional to the square ratio of ME voltage coefficient (MEVC) from each port of the tailored ME samples, which are in coincidence with theory under desired operation stability and favorable experiment repeatability evaluated by uncertainties of 0.25854 V/cm Oe and 0.32979 V/cm Oe for each port. Therefore, a prediction of evolutionary tendency for arbitrary power splitter realization was expanded in view of our experimental observations, and a great flexibility for device future design and further optimization was also provided. Therefore, the presented LF power-splitting strategy paves the ways for arbitrary power splitter realization and enriches the multi-functional ME power electronics families, as well as enables potential applications for efficient excitations of MAs in high-permeable military underwater and civilian emergency rescue distribution long-wave communication system for practical scenarios of submarine, underground railways, tunnels and collapsed residential buildings.

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