Debra S. Rivera1, 2, Turner Robert2
1Univercity Medical Center, Utrecht, Netherlands; 2Neurophysics, Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Saxony, Germany
For transmit elements, mismatch in phase or amplitude of signal delivered to the two sides of a coil element cause common-mode current losses. Using 3-port mixed-mode scattering parameters, the authors compare common-mode rejection (CMR) and insertion loss (IL) of lattice and wire-wound baluns. Transmit efficiency of the different baluns, and a through were compared for a 7T head transmit array. All baluns were tuned to CMR <-20 dB, and provided >20% improbed power efficiency, indicating the severity of common-mode losses for 7T. Transmit efficiency correlated with IL, favoring wire-wound baluns.