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Microstrip Butler matrix design and realization for 7 T MRI.
- Source :
-
Magnetic resonance in medicine [Magn Reson Med] 2011 Jul; Vol. 66 (1), pp. 270-80. Date of Electronic Publication: 2011 Feb 28. - Publication Year :
- 2011
-
Abstract
- This article presents the design and realization of 8 × 8 and 16 × 16 Butler matrices for 7 T MRI systems. With the focus on low insertion loss and high amplitude/phase accuracy, the microstrip line integration technology (microwave-integrated circuit) was chosen for the realization. Laminate material of high permittivity (ε(r) = 11) and large thickness (h = 3.2 mm) is shown to allow the best trade-off of circuit board size versus insertion loss, saving circuit area by extensive folding of branch-line coupler topology and meandering phase shifter and connecting strip lines and reducing mutual coupling of neighboring strip lines by shield structures between strip lines. With this approach, 8 × 8 Butler matrices were produced in single boards of 310 mm × 530 mm, whereas the 16 × 16 Butler matrices combined two submatrices of 8 × 8 with two smaller boards. Insertion loss was found at 0.73 and 1.1 dB for an 8 × 8 matrix and 16 × 16 matrix, respectively. Measured amplitude and phase errors are shown to represent highly pure mode excitation with unwanted modes suppressed by 40 and 35 dB, respectively. Both types of matrices were implemented with a 7 T MRI system and 8- and 16-element coil arrays for RF mode shimming experiments and operated successfully with 8 kW of RF power.<br /> (Copyright © 2011 Wiley-Liss, Inc.)
Details
- Language :
- English
- ISSN :
- 1522-2594
- Volume :
- 66
- Issue :
- 1
- Database :
- MEDLINE
- Journal :
- Magnetic resonance in medicine
- Publication Type :
- Academic Journal
- Accession number :
- 21360739
- Full Text :
- https://doi.org/10.1002/mrm.22777