Research And Design Of A Portable Electrical Receiver

With the development of mineral resources exploration and mining,the mineral exploration work is facing the situation of "difficult to identify,difficult to discover,and difficult to use." The "Thirteenth Five-Year Plan for National Science and Technology Innovation" of the State Council of China clearly proposes "DEPTH" layouts such as " Deep Space,Deep Sea,Deep Land,Deep Blue." Call for the use of deep blue technology,focusing on the search for mineral resources in deep and complex terrain to improve the mineral exploration technology."Deep Ground" includes the exploration of mineral resources and energy resources."Deep Blue" includes network technology,information technology,artificial intelligence,etc.Electrical prospecting is based on differences in electrical conductivity,electrochemistry,magnetic permeability,and dielectric properties between rocks and ores.It observes and studies the distribution law of natural and artificial stable current field or alternating electromagnetic field,and reveal mineral resources or solve geological problems.Electrical prospecting can also explore oil and gas fields,groundwater,archaeological research,geological mapping,etc.During the electrical prospecting,because of the weakness of the measurement signal and the wide dynamic range,the receiver for electrical prospecting needs to have high magnification and wide range of adjustable gain.Because various interference signals of the natural environment are superimposed on the signal,the receiver also requires strong anti-interference ability.The receivers currently on the market are generally large in size and complicated in operation,and high-quality receivers are monopolized by foreign countries.This paper analyzes and studies the related theory of electrical prospecting and its related technology.According the induced polarization method and correlation identification method,a portable receiver is designed for electrical prospecting.This receiver uses the principle of induced polarization method,the transmitter inputs current to the earth.After receiving the returned data,the receiver processes and analyzes the data,and judges the geological distribution in the crust by viewing the data distribution rules,find useful rock ore in the end.The receivers developed in this paper include: low-noise analog front-end circuits,multi-channel data acquisition circuits,FPGA data processing circuits,embedded communication systems,and low-noise highefficiency power management systems.The contents of each part are:(1)The function of the low-noise analog front-end circuit is to selectively amplify the weak signal collected by the receiver probe to improving the signal-to-noise ratio and suppressing interference noise.The circuit mainly includes input port differential low-pass filtering,wide-range differential program-controlled gain and two-stage differential amplifier circuit.(2)The multi-channel data acquisition part is developed around the AD7768-4 analog-to-digital converter,including configuration circuit,clock circuit and communication circuit.Responsible for converting the analog signal conditioned by the front-end analog circuit into a discrete digital quantity for subsequent digital circuits.(3)The FPGA data processing part is responsible for deserialization the high-speed serial signals from the ADC,filtering and processing the data,and time stamping each original sampling point.In the subsequent analysis of the data,not only can the amplitude information be restored offline,but also the information such as the signal propagation time and phase deviation from the transmitter to the receiver.This part includes analog-to-digital converter deserialization,analog front-end programmable gain value control,satellite clock synchronization,sampling point timestamp combination and data transmission.(4)The embedded communication system has designed BDS-based time synchronization,which can effectively avoid the accumulation of local clock errors and keep the local time consistent with the time of the satellite.The system also includes location information recording,user interaction logic based on touch screen,USB disk with file system and SD card read and write design,Bluetooth and Wi Fi communication circuit,etc.(5)The power management part uses a single-cell lithium battery for power supply.The power supply of the portable receiver is completed by the high conversion efficiency of the DC-DC converter and the low noise characteristics of the LDO.Lithium battery power management uses the ampere-hour integration method and a self-learning and updating mechanism for the total battery capacity is designed to ensure the accuracy of the power display.Finally,the research and production of the portable receiver for electrical prospecting made relevant tests: ADC signal acquisition test results show that the analog front-end noise suppression performance is good.In the gain linearity test,its linearity reached 0.99994.In the inter-channel consistency test,its inter-channel error is within 1%.And the receiver is small and light.All the tests of this receiver have met the design expectations.