 Corresponding author: Mohammed K. Al-Obaidi: Al.obaidi.m.k.i@gmail.com Universiti Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia. Copyright © 2022 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0. Rotman lens: Systematic review of simulation approaches Mohammed K. Al-Obaidi 1, 2, * 1 University Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia. 2 College of Engineering, Computer Engineering Department, Al-Iraqia University, Baghdad, Iraq University Tun Hussein Onn Malaysia, 86400 Parit Raja, Batu Pahat, Johor, Malaysia. Global Journal of Engineering and Technology Advances, 2022, 11(03), 079–085 Publication history: Received on 17 May 2022; revised on 22 June 2022; accepted on 24 June 2022 Article DOI: https://doi.org/10.30574/gjeta.2022.11.3.0098 Abstract The beamforming technique is an important factor in designing modern wireless communications systems. While Rotman lens is a vital method to achieve the ability to steer the radiation pattern at the desired locations. Besides, there are many contributions to enhancing the performance of such lens, however, a classification to review this development is required. The main objective in this study objective is to explain and discuss the historical evolution of the Rotman lens as a beamformer based on the simulation methods used to analyze the mathematical model of the Rotman lens. The study shows that the variety of the methods is to achieve accurate simulation results while the simulation time and hardware computer requirements are still a challenge. Keywords: Rotman lens; Fullwave simulations approaches; Electrically large and complex structure; Beamforming 1. Introduction Rotman lens was created as a beamforming network (BFN) in the 1963s and was then used in numerous cutting-edge applications [1]. Rotman lens beamformer works on the assumption of geometric optics. Typically, such a beamforming network is used for a wide-band frequency operation[2], 5G wirelss system[3],and 6G applications [4]. The schematic drawing of a two-dimensional Rotman lens is shown in Figure 1. Where N is referred to the adjacent elements distance and Y is the receive distance from the x-axis. The beam port part includes several radiators in the transmission mode, and it works as receiving radiator in the receiving mode. Besides, each radiated beam is related to an input port. The array port surface consists of several receiving elements that are linked to the array elements through different length transmission lines to save the linearity of phase shifting. The principle of operation in order to generate the out beam in the desired direction can be explained as follow. The excitation is applied to the beam port. Each receiving port directs the received energy from the beam port to the element in the array port. The phase of the received signal is directly proportional to the path length (travelling distance) between the beam port radiator and the receiving element. This model produces a linear phase shift across the radiator elements. Thus, each beam port element is related to a beam at a unique scan angle. Many researchers are motivated to implement a Rotman lens to control the produced beam in the desired location. In radar surveillance systems, these lenses are usually used to see objectives in various directions owing to their multibeam capacity without physically shifting the antenna structure. In the following, the main properties of the microstrip Rotman lens will be described.