Distributed controlled-source electromagnetic methods based on high-order pseudorandom signal

Controlled-Source Electromagnetic (CSEM) methods have increasingly been utilized in diverse fields such as hydrology, engineering geology, and resource exploration. A critical factor in these methods is the design of transmission signals, which significantly affects data collection efficiency and cost-effectiveness. Frequency-Domain Electromagnetic (FEM) methods, based on frequency sounding theory, require the transmission of electromagnetic signals at multiple frequencies to discern electrical properties at varied depths. Historically, variable-frequency modes were used, measuring frequencies sequentially. To enhance efficiency, pseudorandom codes for multi-frequency transmission have been adopted. The study focuses on the integration of high-order 2n sequence pseudo-random signals into land-based and semi-airborne FEM methods. These signals, capable of transmitting multiple frequencies simultaneously, offer substantial benefits in data processing, particularly in large-scale, high-resolution explorations. The use of high-order pseudorandom signals ensures efficient, long-duration data acquisition, proving vital for distributed FEM exploration.