5G and IEEE 802.11ay introduce the use of the millimeter band as one promising solution to provide broadband wireless communication at multi-Gb/s user data rate. Due to the severe path-loss at such frequencies, it is generally assumed that large antenna arrays are used at the base station to steer narrow beams and build highly directional communication links towards the terminal points. However, broader and less directional beams are also of high interest in some of the steps involved in the establishment or the maintenance of the communication links . Indeed, search of a large area by narrow beams becomes too time consuming and link outage becomes more critical, thus affecting the latency and the robustness of the communications. A method enabling an adaptation of the beam widths is then worthwhile to consider. In this article, we investigate how narrow beams naturally produced by large antenna arrays can be broadened to adapt the beam width to a desired angular sector. We consider that the multi-antenna processing is performed by phase shifters on the radio-frequency stage since fully digital beamforming is hardly feasible in practice at such high frequencies. The main idea of our systematic phase-only beam broadening technique relies on the determination of a quadratic phase excitation law from a desired beam width and steering angle. We first lead a thorough analysis of the radiation behavior regarding the coefficients of such quadratic excitation. We then propose a calculation method for determining the polynomial coefficients as a function of the desired beam width and steering angle. This non-iterative beam broadening method is described for boresight and non-boresight directions and is intended for discrete antenna arrays.

5G 和 IEEE 802.11ay 引入了使用毫米波段作为一种有前途的解决方案，以提供多 Gb/s 用户数据速率的宽带无线通信。由于这些频率下的严重路径损耗，通常假设在基站使用大型天线阵列来引导窄波束并建立朝向终端点的高方向性通信链路。然而，在建立或维护通信链路所涉及的一些步骤中，更宽且方向性更小的波束也很受关注。实际上，通过窄波束搜索大面积区域变得过于耗时，并且链路中断变得更加关键，从而影响了通信的延迟和鲁棒性。因此，值得考虑一种能够调整波束宽度的方法。在本文中，我们研究了如何扩大大型天线阵列自然产生的窄波束以使波束宽度适应所需的角扇区。我们认为多天线处理是由射频阶段的移相器执行的，因为在如此高的频率下，全数字波束成形在实践中几乎不可行。我们系统的仅相位光束展宽技术的主要思想依赖于从所需的光束宽度和转向角确定二次相位激发定律。我们首先对这种二次激发系数的辐射行为进行了彻底的分析。然后，我们提出了一种计算方法，用于将多项式系数确定为所需波束宽度和转向角的函数。