Abstract:In the field of underwater electromagnetic communication and detection, electromagnetic sweep interference is very common, and its frequency band coverage is large, which can affect almost all frequencies in the working frequency band and reduce the efficiency of communication and detection. General-purpose noise reduction and filtering methods cannot eliminate the components of electromagnetic sweep interference in the same band as the active signal. Studying effective methods to combat electromagnetic sweep interference and improving underwater signal quality has become an urgent problem in the industry. In view of the above technical problems, this paper proposes to enhance the anti-electromagnetic sweep interference performance of the signal by increasing the signal complexity, that is, suppressing the electromagnetic sweep interference based on the modulation technology. Commonly used modulation methods include linear modulation, nonlinear modulation and digital modulation, among which 2ASK (binary amplitude shift keying), 2FSK (binary frequency shift keying) and BPSK (binary phase shift keying) have the advantages of good anti-interference performance, anti-channel loss and high security. Based on the fact that the bit error rates of the three modulation and demodulation methods are based on white noise, this paper further derives the bit error rate of the three digital modulation methods when only the existing electromagnetic sweep interference, white noise and electromagnetic sweep interference exist at the same time, and simulates the three situations. The simulation results show that the three modulation and demodulation methods can effectively suppress the influence of electromagnetic sweep interference and improve the quality of underwater communication. When dealing with electromagnetic sweep interference, the 2FSK modulation method achieves the best performance.
