# Optimization of Multilayer Absorbers Using the Bald Eagle Optimization Algorithm
## 1 Introduction  
The rapid evolution of modern wireless communication is causing serious electromagnetic (EM) interference. It seems that EM radiation has emerged as the fourth most important source of pollution in the environment, after air, water, and noise. Therefore, there is an increasing demand for the development of appropriate materials and techniques to suppress the consequences of EM radiation, and EM interference and EM compatibility have become very important. The presence of any disturbing EM wave source or an object reflecting the waves from the source affects the measurements and the operation of electronic equipment [1]. It is vital that electronic equipment can perform accurately and reliably with electromagnetic compatibility across a wide frequency range (FR) without any interference [2]. Due to the intense use of most frequency bands, the presence of a disturbing EM wave source at the measurement point causes errors in the measurements. In addition to damaging various systems and devices, EM waves also harm living organisms [3]. Since concealment from enemy targets is one of the most important military needs, research on stealth technology has grown significantly over the past 25 years, the principal goal of which is to minimize the target's scattered EM energy so that it becomes invisible to a radar receiver. The application of functional materials having radar/microwaveabsorbing capabilities is the only feasible solution for the implementation of stealth characteristics [4]. To avoid the abovementioned problems, EM absorber materials are used [5], because, due to their magnetic or dielectric losses, EM absorbers can absorb electromagnetic radiation. In the literature, microwave absorbers were developed in two different ways: multilayer and frequency-selective surface screen-based. Multilayer radar/microwave absorber (MRA/MMA) structures have drawn attention recently due to their improved absorption capabilities [6]. Since the electrical and magnetic permeability of different materials varies according to frequency, the properties of the material used in the structure of the absorber are very important in terms of absorption performance. [PERSON] et al. (1993) identified 16 different types of materials to develop the microwave absorbers using a genetic algorithm (GA), comprising lossless dielectric, lossy magnetic materials, and lossy magnetic with relaxing type materials, all of which are frequency-dependent. A narrow, broad-band microwave absorber with a large angle of incidence is the best design for electromagnetic radiation suppression [7]. Numerous criteria are considered while creating the ideal broadband microwave absorber, including operating frequency, incidence angle, wave polarization, material dielectric constants and permittivity, and layer thickness [8; 9]. In the literature, many parameters are adjusted to obtain the optimum properties of the absorber by using various optimization techniques [10; 11; 12], including the number of layers, dielectric constant, permeability, layer thickness, frequency, angle of incidence, and wave polarization [13]. The main problem in constructing an absorber is to keep the reflection coefficient (RC) of an incident wave on a multilayer structure as low as possible for a variety of frequencies and incidence angles [14; 15]. Numerous studies in the literature address this issue [16; 17; 18]. The RC depends on each layer's thickness and electrical and magnetic properties. In the studies, the RC of multilayer structures is calculated using [PERSON]'s recursive method [15] at every angle of incidence [8; 19; 10]. This formula is used to calculate the RC for both TE and TM polarizations. For normal incidence RC is calculated with the same equation for both polarizations [7]. In this study, multilayer microwave absorber (MMA) designs in various FRs have been realized.