Array Layout Design and Beampattern Optimization for Circular-Array MIMO Sonar with Limited Physical Size

By using a receiving circular array, the traditional active sonar can achieve a 360° view field. However, it suffers from a wide beamwidth and a high sidelobe level under the condition of limited physical size of the circular array. To address this problem, we focus on a circular-array multiple-input multiple-output(MIMO) sonar, and propose the corresponding array layout design and beampattern optimization method. The circular-array MIMO sonar is composed of a circular transmitting array and a circular receiving array. And for the purpose of suppressing the sidelobe level, the radius of the two arrays and the relative rotation angle between them are optimized synchronously. Furthermore, to obtain a low sidelobe beampattern, we calculate the weights on the virtual planar array of the designed circular-array MIMO sonar by solving a convex optimization problem. Specifically, the objective function is established to minimize the sidelobe level and set the mainlobe direction response without distortion, and the Euclid norm constraint on the calculated weights is used to ensure relatively robust beampattern performance. Numerical simulations show that the proposed method can obtain a lower sidelobe level than the traditional active sonar with same physical array size and same mainlobe width.