Symmetrical and Asymmetrical Microstripline-based Transmit/Receive Switches for 7 Tesla Magnetic Resonance Imaging

Abstract

The transmit/receive (T/R) switch is an important device in magnetic resonance imaging scanners whenever T/R radio frequency coils are intended to be used. It is placed between transmit amplifiers and T/R radio frequency coils. The T/R switch adds loss to the RF transmit chain, reducing the delivered power to the coil and increasing the noise figure of the receive chain. Therefore, T/R switches should be designed for as low insertion loss as possible. In addition, they need to handle high power in transmit. In this article, three T/R switches for 7-Tesla magnetic resonance imaging scanners are designed using Eagle, and validated by simulation (HFSS, ANSYS) and measurement. Low reflection coefficients (<-20 dB), low insertion loss (≃0.3 dB), and high isolation (>40 dB) was demonstrated for the designed couplers. The fabricated microstripline-based switches were more robust than a design utiliz ing commercial couplers in terms of heat dissipation, high power capabilities, and lower insertion loss.