| Many countries have developed advanced multifunctional electrical workstation,which is a hot research topic in the world.Because of the foreign technology embargo,the development of synthesized electrical prospecting instrument in China still lags behind international standards.In this situation,research group of China University of Geosciences(Beijing)began to develop “Multifunctional and High-Powerful Pit-Surface Electromagnetic Image System”funded by Ministry of Science and Technology 863 project.The research described in this paper was supported by this subject,and focused on the real time hardware algorithm used in the multifunctional electrical receiver.Several electromagnetic observation methods should be achieved by this receiver,coming with different observing object,data acquisition,operation bandwidth,and output parameters,et al.So special data acquisition and processing method should be developed for specific observation method,which is studied in this paper.And following works have been finished.The digital filtering algorithm was studied.High performance anti-alias filter and power line interference notch filter with low hardware resource occupancy were designed.The notch filter was designed with FIR structure.The fundamental frequency and all of the oddharmonic components within the observing frequency band can be removed by this filter.The theoretical derivation of the notch filter transfer function and hardware implementation for these two filters were introduced in detail in this paper.To increase the robustness of time domain induced polarization(TDIP)method against interference and obtain more detailed secondary field information,an improved data-processing algorithm is proposed here.Complete TDIP voltage decay curve as well as apparent chargeability at any time window were extracted based on precise time localization algorithm.Real time data processing and parameter calculation for spectral induced polarization(SIP)method without synchronizing current data were developed.By using all-phase analysis with automatic window length constraint and “frequency-initial phase table”,complex resistivity measurement was achieved in the absence of complex current acquisition and transmission or precise phase-measuring apparatus.Data acquisition and processing method for controlled source audiofrequency magnetotelluric method was developed.By a combination of several anomaly detection methods as well as abnormal extreme value recognition method,Cagniard resistivity and the impedance phase were obtained under strong disturbances.Quick calibration method using square signal source was introduced.The calibration data was processed by using the correlation detection technique,and high precision calibration results of the receiver were obtained.A broadband signal generator based on pseudo random binary sequence(PRBS)was designed,which can provide analogue MT source for MT\AMT device indoor testing.Key indexes of the required PRBS was determined based on a theoretical analysis,and the hardware design for the new generator was completed,finally the MT and AMT modules of the multifunctional electrical receiver were tested by using this generator indoor.Parameter selection methods,hardware design,and the subsequent generator design are described in details.Finally,the above-mentioned algorithms were verified by a series of indoor and field tests.Results shown that,these data acquisition and processing methods developed in this paper is feasible and valid for the problem of multi-parameter data acquisition in integrated electromagnetic observing instrument. |
