基于Σ-Δ的地震采集系统前置放大器探讨

Discussion on Σ-Δ Technology-based Pre-amplifier of Seismic Data Acquisition System

作为石油勘探中使用的地震数据采集系统,目前主要采用Σ-Δ技术完成A/D转换。而其在整个电压范围内,依线性要求,地震数据采集中的时域起始段大信号与时域后段反射层的小信号,共用同一增益的前置信号放大器,因前置放大器对大信号不能过载,限制了小信号在前端采集时的放大处理。为了更好地在小信号放大上发挥Σ-ΔA/D转换器的强噪声抑制能力、良好的24位处理能力,通过信号分析,提出采用非线性前置放大器的方法,对大、小信号的增益分别处理,并完成了相应的仿真设计。

Σ-Δ technology is normally adopted for A/D conversion who as the seismic data acquisition systems used in oil exploration.For the entire working voltage coverage of the A/D conversion,a common pre-amplifier with the same gain is shared with time-domain large-signals in the initial segment of seismic data acquisition,and small-signals from the rear section of time-domain reflecting layer depending on its linearity requirements.The amplification of small signals during the front-end data acquisition could be limited accordingly due to the consideration that the pre-amplifier should avoid being over-loaded by the large-signals.An approach to the non-linear pre-amplifier for seismic data acquisition systems by means of signal analysis is proposed,in order to improve the performance for small-signal amplification,taking better advantage of the strong noise suppression and excellent 24 b processing capability of the Σ-Δ technology-based A/D converters.Methods to handle gains for both large and small-signals are discussed respectively,the corresponding simulation results are provided as well.