A 3 Tesla (127.72 MHz) Magnetic Resonance system is able to scan with both the body coil and surface coil at the same time due to a technology called simultaneous acquisition, which uses a 4-port power divider, typically a quad hybrid. This functions at 127.72 MHz. The goal is to replicate this function at 1.5 Tesla field strength (63.86 MHz), but to do so would require the power divider to double in size. This space is not available, so methods of miniaturizing the design were investigated. It was found that slow wave structures cannot shrink the quadrature hybrid design enough to fit inside the desired area. Meandering the transmission lines of the hybrid shrinks the design, but is still too large for our application. The use of lumped elements successfully shrinks the design to fit within the desired space.
Both the meander line design and lumped element design were printed on RO4350, a Rogers printed circuit board material. The meander line design meets all of the critical performance requirements, while the lumped element design did not.
The design also had to withstand a variable load and coupling between the coils of the body coil. To test for this, the printed boards were attached to a body coil and a variable attenuator. The meander line design met all the performance requirements and had better performance than the lumped element design.
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|Advisor:||Richie, James, Lee, Chung|
|Department:||Electrical & Computer Engineering|
|School Location:||United States -- Wisconsin|
|Source:||MAI 58/05M(E), Masters Abstracts International|
|Subjects:||Engineering, Electrical engineering|
|Keywords:||Branchline coupler, Hybrid, Miniaturization, Variable load|
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