基于FET主动控制的脉冲核磁共振射频开关电路

NMR RF switch circuit based on FET control

核磁共振技术在工农业生产以及日常生活中都有广泛应用,如石油、天然气、地下水等物质的勘探以及食品化工行业中的在线无损检测等。本文主要介绍了一种新的脉冲核磁共振射频开关。核磁共振射频开关在核磁共振系统中起着重要作用,它能够实现发射通道与接收通道的切换。在核磁共振实验中,开关的切换时间以及死区时间的设定都非常重要,它们直接影响核磁共振信号的纯净度。本文在四分之一波长传输线设计方法的基础上,采用三极管和场效应管相结合的方法来控制开关切换时间,并通过电解电容充放电的方法实现了对死区时间的控制。

NMR technology is widely used in industrial and agricultural production and daily life. For example,it can be used for the exploration of oil,natural gas,groundwater and other material,or nondestructive testing of food chemical industry. In this article a new RF switch used in the NMR system is introduced. The RF switch plays an important role in the Nuclear Magnetic Resonance（ NMR） system. Its function is to switch between the RF transmitting path and the NMR signal receiving path in the NMR system. In the NMR experiment,the switching time and the dead time are very important and they directly affect the purity of the NMR signal. In this paper,a new method based on the traditional quarter-wavelength transmission line is proposed to control the switching time by a combination of transistor and FET circuit,while the dead time can be regulated by means of the charging and discharging of an electrolytic capacitor.