Research on Shallow Surface Frequency-Domain Electromagnetic Transmitting Technology Based on Broadband Impedance Matching Network

The shallow surface frequency-domain electromagnetic (SSFEM) method is a widely used geophysical exploration technique. Aiming at the problem of energy suppression of high-frequency transmitting signals due to the load coil inductance, a novel transmitting scheme with adding a broadband impedance matching network (IMN) based on IGBT controlled series compensation (ICSC) is proposed in this article to the transmitting circuit to increase the current energy at each frequency point in a broadband frequency range, different from the previous impedance matching schemes that are less flexible and only capable of enhancing the current energy for very few fixed frequency points. First, the proposed broadband impedance matching circuit model with continuously adjustable impedance ability is given and its regulation principle is analyzed. Furthermore, the selection principles for network parameter are provided and the differences between ideal and nonideal models are analyzed. Finally, the feasibility and superiority of the proposed broadband IMN scheme are verified by comparative analysis with simulation and experiment with no matching circuit and adding fixed capacitance matching circuit. In the frequency band of
$500\sim 1000$
Hz, the main frequency current amplitude can be increased by more than 17.6% with the proposed technique.