Multi-frequency digital drive signal generation technology in near surface electromagnetic detection domain

To meet the requirements of electromagnetic sounding for emission in the near-surface frequency domain, a System on a Programmable Chip (SOPC) was built using Field Programmable Gate Array (FPGA) as the hardware control platform. The SOPC was based on the unipolar and frequency multiplication Sinusoidal Pulse Width Modulation (SPWM). Verilog was used to realize multi-frequency digital SPWM algorithm, generate the multi-frequency digital drive signal. This signal has a small frequency interval and low Total Harmonic Distortion (THD). It can overcome the defects of other methods, such as the fixed frequency interval and complex system structure of pseudo random method, the over-dependence on load coil and complex algorithm of the bit-stream method. Theoretical simulation and experiment results verify the effectiveness of the method.