The Development and Research of Sine Signal Source with VLF Based on FPGA

摘要

Very Low Frequency (VLF) electromagnetic method is an important means in petroleum exploration. Application of Trenchless guided boring technology broadens the VLF electromagnetic waves in the range of applications in engineering practice. It uses orientation instrument to measure intensity and phase of the specific VLF electromagnetic wave launched by near-bit probe for bit space locating and orientation of drilling information. Comparing the production ways of the VLF signal source, and the characteristics of the principle, this paper presents a VLF standard sine wave signal source design scheme based on DDS and FPGA, the latter uses frequency modulation digital sine signal generator and frequency measurement to produce standard sine wave signal. Invoking coarse and fine adjustment control word, this signal source naturally achieves rapid, continuous and accurate frequency modulation. It's of many remarkable characteristics, such as low signal-noise, low power consumption. The FPGA, compared with the DDS digital synthesis source, is an ideal choice of the new probe signal source, which has a bigger chip memory, more convenient and quick signal modulation, and faster processing speed.