A multi-octave GaN HEMT radio frequency power amplifier with high efficiency and high linearity for 5T multinuclear MRI

Motivation: Multinuclear MRI transmitting system requires RFPAs with higher bandwidth, efficiency, linearity and output power. Due to the lower power density and factor of merit, conventional Class AB MRI broadband RFPA using silicon-based technologies such as LDMOS and VDMOS as gain-stage transistors have insufficient multi-octave capability and low efficiency. Goal(s): The study aimed at improving the broadband performance, efficiency and linearity of multinuclear MRI RFPA. Approach: An RFPA based on GaN HEMT with matching circuits was proposed. Results: The proposed RFPA can achieve 30-300MHz bandwidth, 1kW output, high efficiency and linearity. Impact: GaN RFPA with higher bandwidth, linearity and efficiency can be applied to high-field multinuclear MRI transmitting systems with different field strengths, which brings improvements for scanning sequences with long pulse widths and high linearity requirements.