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Radiofrequency current source (RFCS) drive and decoupling technique for parallel transmit arrays using a high‐power metal oxide semiconductor field‐effect transistor (MOSFET)
Author(s) -
Lee WonJe,
Boskamp Eddy,
Grist Thomas,
Kurpad Krishna
Publication year - 2009
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.21988
Subject(s) - mosfet , transistor , current source , amplifier , electrical engineering , field effect transistor , electrical impedance , decoupling (probability) , optoelectronics , power mosfet , materials science , physics , voltage , cmos , engineering , control engineering
A radiofrequency current source (RFCS) design using a high‐power metal oxide semiconductor field effect transistor (MOSFET) that enables independent current control for parallel transmit applications is presented. The design of an RFCS integrated with a series tuned transmitting loop and its associated control circuitry is described. The current source is operated in a gated class AB push‐pull configuration for linear operation at high efficiency. The pulsed RF current amplitude driven into the low impedance transmitting loop was found to be relatively insensitive to the various loaded loop impedances ranging from 0.4 to 10.3 ohms, confirming current mode operation. The suppression of current induced by a neighboring loop was quantified as a function of center‐to‐center loop distance, and was measured to be 17 dB for nonoverlapping, adjacent loops. Deterministic manipulation of the B 1 field pattern was demonstrated by the independent control of RF phase and amplitude in a head‐sized two‐channel volume transmit array. It was found that a high‐voltage rated RF power MOSFET with a minimum load resistance, exhibits current source behavior, which aids in transmit array design. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.