The Effect of Shell Shape on Self-Interference Signal Strength of In-Band Full-Duplex Underwater Acoustic Communication Modem

Compared with the half-duplex (HD) underwater acoustic (UWA) communication system, the in-band full-duplex (IBFD) UWA communication system can theoretically double the frequency band utilization. The main challenge of the IBFD-UWA communication is to eliminate the self-interference (SI) signal generated by the near-end transmitter. In this paper, we focus on the effect of the dimensions of the IBFD-UWA modem shell on the strength of the SI signal. The typical IBFD-UWA modem is long cylindrical, and its height is higher than the radius; the strength of the SI signal is very high due to the shape of the shell. Therefore, the finite element method (FEM) is used in the simulation software to calculate the SI signal strength received by shells of different dimensions. The simulation results show that when the diameter increases gradually, the SI signal strength reaches a maximum value, and then the diameter approaches the height and then decreases gradually. When the diameter is gradually larger than the height, the energy of the SI signal received by one size increases suddenly, which may be caused by the material resonance frequency. Then the energy of the SI signal decreases sharply. The simulation results provide a useful reference for the design of the IBFD-UWA communication modem shell.