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Low noise analog receiving circuit for nuclear magnetic resonance logging tool

A technology of nuclear magnetic resonance and receiving circuits, which is applied in the direction of construction, can solve the problems of complex structure and low signal-to-noise ratio, and achieve the effect of suppressing low-frequency noise, good high-frequency characteristics, and wide bandwidth

Inactive Publication Date: 2017-04-05
何志杰
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0005] In order to overcome the shortcomings of the existing analog receiving circuit with complex structure and low signal-to-noise ratio, improve the anti-noise performance of the analog receiving circuit, simplify the circuit and improve the signal-to-noise ratio at the same time, the present invention designs a device for nuclear magnetic resonance logging tools Low Noise Analog Receive Circuit

Method used

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  • Low noise analog receiving circuit for nuclear magnetic resonance logging tool
  • Low noise analog receiving circuit for nuclear magnetic resonance logging tool
  • Low noise analog receiving circuit for nuclear magnetic resonance logging tool

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Embodiment Construction

[0016] figure 1 Among them, the output of each stage of amplifying circuit uses a first-order RC high-pass filter to eliminate the influence of the offset voltage of the operational amplifier on the dynamic range of the subsequent stage circuit and suppress low-frequency noise. The last three stages of amplification circuit adopts the non-inverting amplification structure with equal signal gain and noise gain. The eighth-order active band-pass filter with Sallen-Key structure can effectively suppress the circuit noise outside the operating frequency. In order to reduce external noise interference, the analog circuit is installed in an aluminum box, and an iron box is used to shield the circuit board.

[0017] figure 2 Among them, the broadband low-noise operational amplifier LMH6626 and the low-noise operational amplifier OPA2111 with the optimal source resistance of 556 ohms are used as the differential amplifier and subtractor respectively. u 1A , U 1B The non-inverti...

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Abstract

The invention provides a low noise analog receiving circuit for a nuclear magnetic resonance logging tool. In the circuit, an instrument uses an amplifier to eliminate the influence of the offset voltage of an operational amplifier on the dynamic range of a post-stage circuit and suppress low frequency noise. A signal comparator has the characteristics of large input swing, high speed and high precision. The shortcomings of instable open-loop and peak current and average current errors of a PWM modulation circuit in the existing current mode are overcome. The output impedance is improved. The pass band is broadened. The low noise analog receiving circuit has the advantages of great high frequency characteristic, flexible design, stable work and greatly improved signal to noise ratio.

Description

technical field [0001] The invention relates to a low-noise analog receiving circuit, which is suitable for a nuclear magnetic resonance logging instrument. Background technique [0002] The noise sources of the analog receiving circuit are two types: external interference noise and inherent noise inside the circuit. The analog receiving circuit is placed at the front end of the instrument, the purpose is to amplify the weak echo signal received by the antenna with low noise nearby, so as to reduce the noise interference introduced by the echo signal during transmission, and at the same time reduce the number of digital circuits working at high frequency. Interference with receiving circuits, [0003] Its noise performance directly affects the signal-to-noise ratio of the NMR signal and the detection sensitivity of the instrument. The working frequency of nuclear magnetic resonance spectrometer and nuclear magnetic resonance imager is generally not lower than 20 MHz, and t...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): E21B47/13
Inventor 何志杰
Owner 何志杰