TY - JOUR
T1 - Miniaturized tunable extended eight-port hybrid coupler for 1.5 T MRI
AU - Colwell, Zachary A.
AU - Sohn, Sung Min
N1 - Publisher Copyright:
© The Author(s), 2022. Published by Cambridge University Press in association with the European Microwave Association.
PY - 2023/6/3
Y1 - 2023/6/3
N2 - This paper presents a miniaturized, tunable, high-power, eight-port hybrid coupler, based on a lumped element hybrid coupler topology. The 90° hybrid couplers are ubiquitous elements used for feeding RF coils in quadrature in magnetic resonance imaging (MRI) systems. Due to the low Larmor frequency (64 MHz) of 1.5 T MRI, distributed elements are too large for practical circuits to drive multi-port RF coils. Thus, miniaturization with MRI-compatible, non-magnetic, and high-power components is necessary. First, a miniaturized hybrid coupler is proposed for MRI systems with non-magnetic variable capacitors. Afterwards, the miniaturization methodology is applied to develop an eight-port coupler, capable of supporting both a transmit and a receive quadrature RF coil system. The high-power (up to 1 kilowatt) extended coupler measures 10 cm × 6 cm. Test results show that each port has a return loss of more than 16 dB, each input-isolated port is isolated by more than 24 dB, and each output has an insertion loss of less than 2.5 dB and output phases of 0.0°, 90.8°, 182.1°, and 278.7°.
AB - This paper presents a miniaturized, tunable, high-power, eight-port hybrid coupler, based on a lumped element hybrid coupler topology. The 90° hybrid couplers are ubiquitous elements used for feeding RF coils in quadrature in magnetic resonance imaging (MRI) systems. Due to the low Larmor frequency (64 MHz) of 1.5 T MRI, distributed elements are too large for practical circuits to drive multi-port RF coils. Thus, miniaturization with MRI-compatible, non-magnetic, and high-power components is necessary. First, a miniaturized hybrid coupler is proposed for MRI systems with non-magnetic variable capacitors. Afterwards, the miniaturization methodology is applied to develop an eight-port coupler, capable of supporting both a transmit and a receive quadrature RF coil system. The high-power (up to 1 kilowatt) extended coupler measures 10 cm × 6 cm. Test results show that each port has a return loss of more than 16 dB, each input-isolated port is isolated by more than 24 dB, and each output has an insertion loss of less than 2.5 dB and output phases of 0.0°, 90.8°, 182.1°, and 278.7°.
KW - Antenna feed
KW - hybrid coupler
KW - magnetic resonance imaging (MRI)
KW - passive circuits
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U2 - 10.1017/S1759078722000927
DO - 10.1017/S1759078722000927
M3 - Article
AN - SCOPUS:85169295480
SN - 1759-0787
VL - 15
SP - 805
EP - 809
JO - International Journal of Microwave and Wireless Technologies
JF - International Journal of Microwave and Wireless Technologies
IS - 5
ER -