Hybrid‐pair ratio adjustable power splitters for add‐on RF shimming and array‐compressed parallel transmission

Zhu, Y.S.; Lü, Ming; Grissom, William A.; Gore, John C.; Yan, Xinqiang

doi:10.1002/mrm.28934

Cited by 3 publications

(3 citation statements)

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“…As expected, the simulated losses were lower than the bench measurements. The average loss of 6.22% on the bench is low given that the previous iteration of RAPS circuits have reported 10% 25 and 7.31% 26 . The magnitude of loss and accuracy of the ratios held for the two‐stage cascaded network as well, indicating that these circuits can be cascaded to drive many more coils from a single transmit channel.…”

Section: Resultsmentioning

confidence: 91%

“…CAD, computer-aided design 7.31%. 26 The magnitude of loss and accuracy of the ratios held for the two-stage cascaded network as well, indicating that these circuits can be cascaded to drive many more coils from a single transmit channel.…”

Section: Experimental Validation: Phantom Imagingmentioning

confidence: 95%

“…For such fixed networks, matching the target and realized compression weights while minimizing power loss, size, and complexity is paramount. While fixed phase shifts can be implemented using transmission lines, relative attenuations are more challenging because of large differences in the impedance needed, and ratio‐adjustable power splitter (RAPS) circuits have been developed using lumped elements and coaxial cables 25 and commercial hybrid couplers 26 for this application. However, each of these solutions has some drawbacks, including large numbers of lumped elements and screw connections, which leads to large sizes and/or power losses, or mechanical connections that may affect reliability.…”

Section: Introductionmentioning

confidence: 99%

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On the design and manufacturing of miniaturized microstripline power splitters for driving multicoil transmit arrays with arbitrary ratios at 7 T

et al. 2022

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The purpose of the current study was to implement unequal microstrip power splitters for parallel transmission at 7 T that are optimized for size and loss and that can be configured for a wide range of power ratios. The splitters will enable the use of more transmit coils without a corresponding increase in the number of transmit channels or amplifiers to control specific absorption rate, shorten RF pulses, and shim inhomogeneous RF fields. Wilkinson unequal power splitters based on a novel microstrip network design were optimized to minimize their size under 8 cm in length and 9 cm in width, enabling them to be included in coil housing or cascaded in multiple stages. Splitters were designed and constructed for a wide range of output power ratios at 298 MHz. Simulations and bench tests were performed for each ratio, and a methodology was established to adapt the designs to other ratios and frequencies.The designs and code are open source and can be reproduced as is or reconfigured.The single-stage designs achieved good matches and isolations between output ports (worst isolation À15.9 dB, worst match À15.1 dB). A two-stage cascaded (one input to four outputs) power splitter with 1:2.5, 1:10, 1:3, and 1:6 ratio outputs was constructed. The worst isolation between output ports was À19.7 dB in simulation and the worst match of the three ports was À17.8 dB. The measured ratios for one-and two-stage boards were within 10% of the theoretical ratios. The power-handling capability of the smallest trace was approximately 70 W. Power loss for the one-and two-stage boards ranged from 1% to 3% in simulation compared with 5.1% to 7.2% on the bench. It was concluded that Wilkinson unequal microstrip power splitters can be implemented with a small board size (low height) and low loss, and across a wide range of output power ratios. The splitters can be cascaded in multiple stages while maintaining the expected ratios and low loss. This will enable the construction of large fixed transmit array-compression matrices with low loss.

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Section: Resultsmentioning

confidence: 91%

Section: Experimental Validation: Phantom Imagingmentioning

confidence: 95%