Research Of Time-Frequency Electromagnetic Transmitter System Based On FPGA

With the rapid development of China's economy,the demand for resources such as metals and petroleum is increasing day by day,and the detection scale is increasing gradually.The detection depth is also increasing,and the requirements for detection instruments are getting higher and higher.After years of development,electronic technology and electromagnetic exploration theory are constantly evolving.The previous electromagnetic emission system was designed separately for the time domain electromagnetic method and the frequency domain electromagnetic method.With the development of chip technology makes the chip smaller and smaller,its performance is getting higher and higher.Most of the transmitters on the market are mostly foreign,although the domestic also appeared in a better electromagnetic launch system,its function is relatively simple.Making the design of a time-frequency electromagnetic emission system has a very important significance.This paper is based on the “The research of half aviation transient electromagnetic exploration technology based on unmanned aerial vehicle”.The project improved the transient electromagnetic method,which is the time domain electromagnetic method.In order to improve the versatility of the transmitter,a time-frequency electromagnetic transmitter system is designed and studied experimentally.The transmitter meets the time domain electromagnetic and frequency domain electromagnetic methods of the transmitter requirements.This article will introduce the following aspects to the design of time-frequency electromagnetic transmitter.The present situation and development trend of electromagnetic transmitter at home and abroad are studied.The principle of various electromagnetic methods is introduced.Based on this,the composition principle of time-frequency electromagnetic transmitter system is analyzed.The pulse waveform of time-domain electromagnetic method and frequency electromagnetic method is different.In general,the time domain electromagnetic transmitter is a bipolar square wave pulse signal.The frequency domain electromagnetic transmitter emits a waveform which is an alternating square wave pulse signal.Pseudo-random signal method requires a pseudo-random multi-frequency wave.Combined with the existing half aviation transient electromagnetic transmitter design ideas,designed a time-frequency electromagnetic transmitter.The paper completes the hardware circuit design of the system.The system uses a microcontroller and FPGA control circuit,and the design of the corresponding external circuit.Including the design of the transmitter control circuit,the system power supply circuit design,H bridge and its drive circuit design and voltage and current monitoring circuit design.The transmitter control circuit generates the various operating waveforms required by the transmitter through a microcontroller and an FPGA.The system power supply circuit is used to supply power to each module.H bridge and its drive circuit uses two sets of turns on the voltage waveform to drive IGBT.Voltage and current monitoring module is mainly designed AD circuit and USB transmission module.The software part is based on the hardware part of the carrier.Introduce the SCM part of the program development and Verilog language to achieve the development of FPGA.The control flow chart of the transmitter is programmed to realize the functions of working waveform generation,data communication,data acquisition,system monitoring and liquid crystal display.After the design of the transmitter is completed,the type and frequency of the waveform of the transmitter are tested.The pseudo-random multi-frequency signal is analyzed in LabVIEW,and it is determined that the indexes of the transmitter are expected.However,the system debugging and practical application remain to be achieved.