Dual Tuned Switch for Dual Resonance 1H/13C MRI Coil

This paper introduces two transmit/receive switch designs for 7 Tesla magnetic resonance spectroscopic imaging. Both designs based on microstripline-based couplers. The first is a dual-tuned 1H/13C switch with two concentric microstriplines on each side of the switch. A branch line technique from transmission line theory is applied to compact the switch to half of its initial dimension. The second proposed design is a dual tuned 1H/13C microstripline-based switch with one microstripline in each side of the switch. The second design benefits from the harmonics of an initial resonance signal to shift the first and second harmonics to the same Larmor frequencies of the 1H and 13C nuclear spins when exposed to 7 Tesla static magnetic field. The first design serves 1H and 13C RF Coils, working independently. Whereas the second design works with a dual resonance 1H/13C RF coil. The first and second designs achieved good matching less than -15 dB and -10 dB, respectively. They achieved low insertion loss less than -0.6 dB and -1.2 dB, respectively. The isolation between couplers in the first design is higher than 60dB. Furthermore, the isolation between the amplifier port and the receiver for both switches designs are higher than 60dB as well. The proposed switches are promising in reducing the number of T/R switches and the area of the place they need in the transmit front-end when multichannel RF coils are used.