基于信号调制的抗水下电磁扫频干扰方法研究

Research on Anti-underwater Electromagnetic Sweep Interference Method Based on Signal Modulation

摘要:

在水下电磁通信和探测领域，电磁扫频干扰十分常见，其频带覆盖范围大，几乎可以影响工作频带内的所有频率，降低通信与电磁探测效率。通用的降噪与滤波方法无法消除电磁扫频干扰中与有效信号同频带的成分。研究有效对抗电磁扫频干扰的方法，提升水下信号质量成为业界亟待解决的问题。针对上述技术难题，本文提出通过增加信号复杂度的方式增强信号抗电磁扫频干扰性能，即基于调制技术压制电磁扫频干扰。常用的调制方式包含线性调制、非线性调制和数字调制等，其中2ASK（二进制幅移键控）、2FSK（二进制频移键控）与BPSK（二进制相移键控）具有良好的抗干扰性能、抗信道损耗和高安全性等优点。基于三种调制解调方法的误码率均建立在白噪声的基础上，本文进一步推导了三种数字调制方式在仅存电磁扫频干扰以及白噪声、电磁扫频干扰同时存在时的误码率，并针对三种情况进行仿真研究。仿真计算结果表明三种调制解调方式均能有效抑制电磁扫频干扰的影响，提高水下探测质量。在应对电磁扫频干扰时，2FSK调制方式取得最佳性能。

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.