T- and Cascaded Pi-Shaped 1H T/R Switches with Realistic Trace Width for 7 Tesla MRI"

Abstract

In this work, two designs of Transmit/Receive (T/R) switches are introduced for 7-Tesla magnetic resonance imaging. The T-shaped and the two cascaded Pi-shaped microstripline-based T/R switches for 1H MRI are designed with the minimum trace width constraint that handles the required power and assures a compact size of the switch. When the peak power of the Radio Frequency (RF) amplifier signal is 1 kW with 10% duty cycle, the average current that will pass through 50 Ω input impedance circuit is 2 A. Based on IPC 2221 standard for PCB traces, the minimum trace width that handles such a current is of 0.513 mm. The ADS software is used in designing the T as well as two sections pi-shaped switches. All the proposed 7-Tesla 1H MRI switches have revealed good matching (<-20 dB), low insertion loss (<0.34 dB), and high isolation (>60 dB) during transmit and receive. The designed switches are compact in size by around 40% reduction in dimensions compared to a conventional switch size (100 mm × 100 mm) without folding.