Analog Front-end Design For VLF Receiver System And Applications

Extremely low frequency(ELF)and very low frequency(VLF)radio wave spectrum provides a wealth of information in the study of geophysical phenomena and near-Earth space environment.VLF receiver is a low noise,high sensitivity receiver system for monitoring ELF and VLF radio wave signals emitted by natural radiation and artificial stations.VLF receiver is widely used in solar activity monitoring,space-based remote sensing of Earth,lightning location,global maritime communication and navigation systems,etc.The signal of the VLF artificial station using MSK modulation has constant envelope and phase continuity characteristics.When applied to ionospheric ground-based remote sensing and solar activity monitoring,the amplitude and phase variations in the received signal VLF station is an effective means of temporal changes of D region of ionosphere.In this paper,the current and voltage converter is used to design the the very low frequency receiver analog front-end.From the antenna model,consider the bandwidth requirements of broadband VLF receiver noise and environmental requirements,The simulation and actual production debugging of the current-to-voltage converter complete the implementation of the hardware of the VLF receiver front-end.Design virtual magnetic loop antenna test circuit to test analog front-end hardware and sample data via VLF digital receiver.For the artificial station signal.Firstly,the basic principle of MSK signal modulation and demodulation and the characteristics of MSK signal are introduced.The simulation analysis of MSK signal modulation and demodulation is carried out by Matlab and the characteristics of MSK signal are deeply understood.Then,using the software radio idea to demodulate the signal of the VLF artificial station,and analyze the characteristics of the additional phase function of the MSK signal.Finally,the FPGA is used to implement MSK signal demodulation and verify the processing result.Based on the data of the VLF receiver,three methods for solving the signal phase of the VLF artificial station in the ionospheric detection are introduced and the corresponding data processing platform is designed.According to the results of the data processing platform,the basic variation characteristics of the artificial station signals are analyzed and compared with the LWPC model to verify the correctness of the processing method.Using the GOES satellite solar flare flux data to compare the amplitude data of the VLF receiver,statistically analyze the response of the VLF receiver amplitude data to the solar flare event.The design and test of the VLF receiver analog front-end hardware and the data processing method verification and statistical analysis results show the reliability and practicability of the data and algorithm.