Research On Key Circuits Of Magnetic Resonance Imaging Receiver

The application of multi-coil array can greatly improve the performance of magnetic resonance imaging system,such as image resolution,acquisition speed and scanning time.Therefore,current commercial magnetic resonance imaging scanners all adopt multi-coil structure.However,as the number of coils increases,the system cost,size and complexity also increase which has become one of the major bottlenecks.In order to solve the above problems,the basic solution is to use low-cost and highly integrated CMOS circuits to reduce the bulky and expensive electronic interfaces.However,the design of magnetic resonance imaging receivers is difficult.Not only does it need to design a matching network to decouple the coils,but also less noise figure need to obtain.Based on the traditional decoupling network,the ATF-54143 and Ga As solution are implemented.The latter completes layout-level simulation.Both input impedance are lower than 2Ω.The gains are higher than 20 dB and the NF are lower than 0.5 dB which successfully meet the performance requirements.The low noise and highly integrated CMOS receiver front-end is implemented.Instread of the classic decoupling network,a new decoupling and low-noise network is designed and applied which is suitable for CMOS receivers with micro-sized coils.This network has more freedom in selecting passive components and realizes a pre-amplification effectively reducing the design difficulty of subsequent circuit.On the premise of completing decoupling,the topology design and analysis are performed for the key circuit modules,including low-noise V_t/R bias circuits,current-reuse differential cascode low-noise amplifiers,single signal controling variable gain amplifier and high-isolation low-noise mixer.Based on the TSMC 40nm CMOS process,the low-noise and highly integrated magnetic resonance imaging receiver system effectively achieves maximum gain of 110 dB and a dynamic gain range of 20.9 dB.The overall power consumption is 41.9m W.The DSB NF at the output of 20k Hz is only1.03 dB.Compared with GaAs implementation solutions,the receiver has characteristics of high integration and low power consumption.Compared with other CMOS integrated receivers,this solution effectively optimizes the noise performance under the premise of decoupling between coils.And it is expected that the receiver has a better application prospect in the magnetic resonance imaging system.