浅海大孔径时钟弱同步阵列的信道匹配阵形校准

A channel matching shape-estimation method for a large aperture array with loose time synchronization in shallow water

浅海大孔径时钟弱同步阵列的阵形校准,受到时钟偏移与信道频散的不利影响,校准精度难以满足探测要求。利用浅海波导环境中仅激发一阶模态的低频段校准信号,使用基于波导参数计算的相速度开展信道匹配距离测量,并将时钟偏移作为未知参数纳入校准模型,结合声源与参考阵元的位置信息,从而消除频散效应和时钟偏移的不利影响,可实现浅海大孔径阵列阵元位置与时钟偏移的信道匹配联合校准。实验数据分析结果表明,该方法有效校准浅海大孔径时钟弱同步阵列的阵元位置和时钟偏移,较之基于时延估计的传统方法,所提方法校准后的15阵元860 m大孔径水平线阵列,对正横和端射方向附近15~30 Hz目标信号的测向精度分别提高了0.2°和0.4°,阵增益分别提高了1.8 dB和4.4 dB。

Accurate Shape-estimation for a large-aperture bottom-mounted array in shallow water is required for the target detection,which is often degraded by the channel dispersion and asynchronous clock.A shape estimation method is proposed for a large-aperture bottom-mounted array whose elements are loosely synchronized in time.The low-frequency active emissions,which excite only the first order normal modes in the waveguide,are used as the calibration signals.The phase velocity across the frequency band is calculated based on the channel parameters,and used to eliminate the negative influence of the modal dispersion.With the GPS information of the sources and the reference array element,the element positions as well as their clock offsets are estimated.The experimental data are used to demonstrate the superior performance of the proposed method for the array shape and clock offset estimation for various parameter-mismatched scenarios.The results on real data collected at sea with a 860-m-long array with 15 sensors demonstrate that the accuracy of the direction-of-arrival estimation and the array gain are improved by 0.20 and 1.8 dB for the broadside targets,0.4°and 4.4 dB for the end-fire targets respectively.