The Research On Master Control System Of Small Digital Nuclear Magnetic Resonance

Low-field NMR technology is an effective means of process monitoring and quality control,its research have great significance.Based on the introduction of nuclear magnetic resonance technology,the paper analyze the advantages of low field nuclear magnetic resonance technology.The influence of miniaturization and digitization of the master control system of nuclear magnetic resonance on the whole nuclear magnetic resonance spectrometer are also analyzed.The main control system is composed of field programmable gate array(FPGA)as the main control chip,which generates timing control signals,controls the transmission of CPMG pulse,and completes high-speed acquisition,processing and upload communication of echo signals.In this system,direct digital synthesizer(DDS)technology is used to achieve the transmition and reception of broadband pulses.In echo signal acquisition and processing module,digital phase-sensitive detection technology is introduced to extract effective echo signals through quadrature demodulation and Finite Impulse Response(FIR),which can reduce the amount of calculation and provide real-time testing.FT2232 D is used as the communication chip,which reduces the trouble of writing USB protocol in the program.And we can write the host computer by ourselves or use the ready-made serial port debugging assistant as the data receiving tool.The circuit design structure of this paper is simple,practical,stable and reliable,which improves the burden of using digital signal processor DSP + FPGA as the main control chip,reduces the circuit volume,and realizes the miniaturization and digitization of the main control system.