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在水下无人航行器(UUV)远程水声通信中利用基阵形成多波束接收信号可以提高接收信噪比,降低通信误码率。但是由于信源与UUV间的相互运动,在接收端需要通过波束切换算法选择输出信噪比最高的波束。由于UUV的通信接收基阵阵元数少,导致接收多波束旁瓣级较高。在这种情况下,对M元频移键控(MFSK)信号调制方式来说,直接比较接收多波束输出信号在通带内能量大小的时域波束切换算法(TDSB)无法正确选择输出信噪比最高的波束,导致通信误码率高。针对这一问题,提出了一种频域波束切换算法(FDSB)。该算法通过在频域中比较各波束输出信号功率谱峰值的大小对波束进行选择、切换。湖上试验结果表明:当通信距离为25 km时,应用TDSB算法无法正确估计输出信噪比最高的波束,通信误码率高。而应用文中提出的FDSB算法,经波束输出后与单阵元接收相比信噪比有5 dB的提高、通信误码率小于10-4。
The use of an array to form multi-beam receive signals in UUV underwater acoustic communications can improve the received signal-to-noise ratio and reduce the communication error rate. However, due to the mutual movement between the source and the UUV, the receiving end needs to select and output the beam with the highest signal-to-noise ratio through the beam switching algorithm. Due to the small number of UUV communication receiving array elements, the receiving multi-beam sidelobe level is higher. In this case, the time-domain beamforming algorithm (TDSB), which directly compares the energy of the received multi-beam output signal in the passband, can not correctly select the output signal noise for M ary frequency shift keying (MFSK) signal modulation Than the highest beam, resulting in high bit error rate. To solve this problem, a frequency domain beamforming algorithm (FDSB) is proposed. The algorithm selects and switches the beam by comparing the peak power spectrum of each beam output signal in the frequency domain. Experimental results on the lake show that when the communication distance is 25 km, the TDSB algorithm can not correctly estimate the beam with the highest output signal-to-noise ratio, and the communication error rate is high. However, the FDSB algorithm proposed in this paper improves the signal-to-noise ratio by 5 dB compared with single-element reception after beam output, and the bit error rate of communication is less than 10-4.