| Weak-signal-detection is the key technology of the advanced logging tools. This thesis is based on the basic theory of Weak Signal Detection, optimizes and designs a new pre-amplifier, and develops a new method in designing and optimizing the band-pass filter, which made a breakthrough progress in the detection of the hundred-n volt level array induction signal.Based on the research status of the array induction imaging logging tools, receiver sections contained pre-amplifier and bandpass-filter have been optimal designed in this thesis. For the old pre-amplifier has limitation in denoising, this thesis has developed a optimizing method, then the simulation of the power waste, noise performance, noise figure has been carried out. Through comparison between the older pre-amplifier and the optimize pre-amplifier. We know the power waste has reduced from 0.406 watt to 0.198 watt. The noise figure of the optimize pre-amplifier has been reduced from 14dB to 2.02dB. In addition, the band-pass filter of the whole receiver section is analyzed in detail. Then a new method of designing the band-pass filter is given based on Orcad/Pspice simulation. Results based on simulation analysis show that this band-pass filter can meet the need of product design. Sensitivity Analysis of the band-pass filter has also been done, so the key components are given.At last, In order to validate the improved scheme, this thesis uses Digital Phase Sensitivity Detection, combined with the attenuator and magnify circuit, results of experiment based on simulation analysis and calculation show that the optimize pre-amplifier and band-pass filter can realize the reliable detection of the a hundred-n volt level array induction signal, which achieve the expected target. |
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