单基地多输入多输出声呐的方位分辨力

为了研究波形分集和发射子阵对多输入多输出(multiple-input multiple-output:MIMO)声呐方位分辨力的影响,建立了同时适用于MIMO声呐和传统有源声呐的远场和近场波束图推导模型,证明了这两种声呐具有相同的方位分辨力。首先,将MIMO声呐发射阵划分为子阵无重合与子阵有重合两种情况,并对传统有源声呐的发射阵也进行相同的划分。据此,推导出两者的远场和近场阵列流型向量均可表示为发射与接收阵列流型向量的直积。接着,利用阵列流型向量的一致性证明了波束图(远场和近场)的一致性。进一步地,证明了发射子阵有重合的情况等效于对发射阵列进行幅度加权(发射阵列中间部分的阵元权值大于两端部分的阵元权值),其可获得更低的波束图旁瓣级但不能提高方位分辨力。理论分析与仿真结果表明:MIMO声呐的有效孔径等于发射与接收联合孔径,其方位分辨力由发射与接收阵列结构所决定,波形分集和发射子阵并未带来更高的方位分辨力。 

On angle resolution of mono-static multiple-input multiple-output sonar

To study the role of the waveform diversity and the transmitting subarray on the angle resolution of the multiple-input multiple-output (MIMO) sonar, the far- and near-field beampattern derivation model, suitable for both MIMO and traditional active sonars, is proposed; and the sameness on angle resolutions of the two sonars is proved. Firstly, the MIMO and traditional active sonars are set to share the same array configuration, and the transmitting array is divided into two types:with overlapped and with non-overlapped subarrays. Then the array manifold vectors of the two sonars are proved to be the same, equaling to the Kronecker product of manifold vectors of transmitting and receiving arrays. Finally, the beampatterns (both in the far- and near-fields) of the two sonars are proved to be the same. prthermore, it is proved that the adoption of overlapped transmitting subarrays can be considered as the amplitude weighting on the transmitting array (where the weights in the array center area are bigger than those in the array marginal area), which reduces the beampattern sidelobe level but not increases the angle resolution. Theoretical analysis and numerical simulations show that the angle resolution of the MIMO sonar is determined by the configurations of transmitting and receiving arrays; the waveform diversity and the transmitting subarrays bring no superior angle resolution for the MIMO sonar.