Abstract #1567

MEMS-based Ratio Adjustable Power Splitters for in-bore Switching of Transmit Array Compression Networks

Charlotte R Sappo^1,2, Gabriela L Gallego³, Xinqiang Yan^2,4, and William A Grissom^1,2,4,5

¹Department of Biomedical Engineering, Vanderbilt University, Nashville, TN, United States, ²Vanderbilt University Institute of Imaging Science, Nashville, TN, United States, ³Department of Electrical Engineering and Computer Science, Vanderbilt University, Nashville, TN, United States, ⁴Department of Radiology, Vanderbilt University, Nashville, TN, United States, ⁵Department of Electrical Engineering, Vanderbilt University, Nashville, TN, United States

A large number of coils in parallel transmission enables higher excitation accuracy with lower SAR, but the high cost and siting challenges associated with transmit amplifiers and their cabling has limited the number of channels to 8 on most 7T scanners. Array compressed parallel transmission overcomes this limitation using hardware networks that enable a large number of coils to be optimally driven by a small number of channels. These networks comprise ratio adjustable power splitter (RAPS) circuits that use hybrid couplers with reflection capacitors to apply relative phase shifts between signal branches that can be tuned to set the power ratios of the coil outputs. Here we describe and evaluate a MEMS-RAPS circuit that uses MEMS switches to switch between terminator capacitors, allowing dynamic remote tuning of output power ratios for more flexible transmit array compression networks.

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