文档介绍：华中科技大学
硕士学位论文
核磁共振测井仪信号检测电路设计与实现
姓名:张凯
申请学位级别:硕士
专业:检测技术与自动化装置
指导教师:孔力
20070208
摘要
微弱信号检测电路是核磁共振测井仪的重要组成部分。本文依据噪声理论,讨
论了微弱信号检测电路的低噪声设计原则,研制了用于核磁共振测井仪的微弱信号
检测电路,可实现纳伏级信号的可靠检测。该研究工作对于正确获取核磁共振信号
具有重要意义。
本文首先简要介绍了核磁共振测井基本原理,核磁共振信号产生的机理及特征,
从总体上确立了检测电路的设计方案。在此基础上,重点论述了为实现前置放大电
路的高增益、宽带宽和低噪声而采用的关键性设计和应用,包括以 MAT02 为核心的
低噪声放大模块设计、OP160 放大模块设计、电源滤波器设计和传输线变压器的应
用等。根据低噪声设计原则,定量分析前置放大电路中各个噪声源的影响,并建立
了电路的等效噪声模型,完善电路设计方案。利用 PSpice 仿真软件对前置放大电路
进行了直流工作点、交流小信号和瞬态分析,进一步完善设计方案。在电路实现过
程中,从器件选型、线路板布局、布线技术、各模块参数校正、电磁屏蔽以及接地
技术等方面充分考虑,以确保电路的低噪声设计。然后简要介绍了滤波放大电路和
数字相敏解调(DPSD)算法软件的设计。
最后介绍前置放大电路、滤波放大电路和整个信号检测电路的性能测试与分析,
并对最小信号的获取给予了阐述和验证。实验证明,该电路的增益带宽为
400kHz~850kHz,且所能获取的信号最小峰峰值小于 50nV,较好地达到了课题研究
的技术要求。

关键词:低噪声设计前置放大核磁共振测井
I
Abstract
With the guidance of low level signal detection method and low noise design theory,
this thesis has cognized and developed a low level signal detection circuit used in Nuclear
ic Resonance Logging Tool, which can realize the reliable detection of the n-volt
level Nuclear ic Resonance Signals.
The thesis introduces the basic theory of Nuclear ic Resonance Logging, the
mechanism and character of the Signals. The scheme of the circuit is planned in total.
On this basis, the concrete realizing scheme and the hardware block diagram of this
signal detection platform are proposed, the emphases of description are put on the key
techniques adopted to improve the performance of signal detection, including the design
of low noise amplifier module based on MAT02, the amplifier module based on OP160,
the power filter and the application mon-mode inductance. Go a step further to
simulate in bias point detail, AC sweep and transient analysis, in order to perfect the
preamplifier realizing scheme with PSpice. In the course of the circuit realization, the
selection of parts of the apparatus, composition and wiring of PCB, argument adjustment
of each module, ic shielding and ground connection are token int