一种无磁化的5 T磁共振射频功率放大器设计

Design of a 5 T Non-magnetic Magnetic Resonance Radio Frequency Power Amplifier

本文介绍了一种可以不接环形器,并在扫描间使用的5 T磁共振射频功率放大器(RFPA).该RFPA基于驻波高耐受的横向扩散金属氧化物半导体(LDMOS)功率管进行设计,共包含三级放大电路.针对传统磁共振RFPA中带磁芯的传输线变压器进行了无磁化的设计,加强了对反射功率的监控,采用模拟负反馈技术实现了对RFPA非线性的自动矫正.测试结果显示该RFPA的输出功率为2 kW,在负载扰动(反射系数Г<0.5)时,40 dB动态输入范围,其增益线性度≤1 dB,相位线性度≤10°,满足成像需求,验证了该设计方案的合理性与可行性.

This paper introduces the design and implementation of a 5 T magnetic resonance radio frequency power amplifier(RFPA),which can be used in scan rooms without a circulator.The RFPA was designed based on laterally-diffused metal-oxide semiconductor(LDMOS)power tube with high standing wave tolerance,and it contained a three-stage amplifier circuit.The transmission line transformers with magnetic core in RFPA was designed as non-magnetic.The reflected power was monitored tensely.The nonlinear automatic correction of RFPA was realized by using analogic negative feedback technology.The results showed that the output of RFPA power is up to 2 kW,the gain linearity performance is less than or equal to 1 dB,and the phase linearity performance is less than or equal to 10 deg over 40 dB range up to rated power during the load disturbance(reflection coefficientГ<0.5),which meets the imaging requirements.Thus the rationality and feasibility of the proposed design scheme are verified.