This paper considers jointly designing the digital beamformer (DBF) and analog beamformer (ABF) for multi-user downlink hybrid beamforming systems in order to enhance communication performance and reduce information leakage. Our goal is maximizing the minimum signal-to-interference-plus-noise ratio (SINR) while depressing the maximum sidelobe level (SLL) of all users. Since the problem is difficult to solve optimally due to its nonconvexity and the infinitely many sidelobe constraints, we analyze the upper bound of the power in the side lobe region and convert the infinite sidelobe level constraints into a finite number of constraints to reduce the complexity of the hybrid beamformer (HBF) design. Then we transform the DBF design and the ABF design problems into convex problems. Based on alternating optimization and semidefinite relaxation (SDR) techniques, we solve the problem effectively. Simulation results show that the proposed algorithm is envisioned to balancing the SINR of all users while effectively depressing the sidelobe level.

本文考虑联合设计用于多用户下行链路混合波束成形系统的数字波束成形器（DBF）和模拟波束成形器（ABF），以增强通信性能并减少信息泄漏。我们的目标是在降低所有用户最大旁瓣电平（SLL）的同时，使最小信号干扰加噪声比（SINR）最大化。由于该问题的非凸性和无限多的旁瓣约束很难解决，因此我们分析了旁瓣区域的功率上限，并将无限旁瓣电平约束转换为有限数量的约束以降低复杂度。混合波束形成器（HBF）设计。然后，我们将DBF设计和ABF设计问题转换为凸问题。基于交替优化和半定松弛（SDR）技术，我们有效地解决了该问题。仿真结果表明，该算法在有效降低旁瓣电平的同时，可以均衡所有用户的信噪比。