# The Impact of an Electric Machine Body on EM Wave Propagation in RTMS
## 1 Introduction  
Rotating electrical machines are ubiquitous across numerous sectors, and their monitoring has become a constant concern in industrial domains such as aviation and nuclear power. Surveillance techniques play a critical role in ensuring the reliability of industrial systems, preventing failures that could lead to physical damage [1, 2]. Typically, the success of these techniques hinges on a thorough understanding of both internal and external characteristics of the machine. Various monitoring methods have been proposed [3, 4]. Generally, these methods can be categorized as human experience-based knowledge methods, analytical redundancy methods based on mathematical modeling of the system, and signal modeling methods. The challenge posed by using these various methods lies in the fact that internal parameters (rotational) are not practically accessible. To address these issues, we propose a new technique for monitoring electrical machines and primarily for the detection of rotational defects. This technique relies on a wireless transmission chain that allows for online supervision of various parameters. Indeed, for several years, the market for wireless networks has undergone significant evolution and continues to do so to offer users new multimedia services [5, 6]. The effectiveness of communication systems in electrical machines is significantly influenced by the complexity of their components [7]. Our research aims to explore how the limited space within the transmission module impacts communication performance. To facilitate this investigation, one antenna is placed inside the machine, while another is fixed externally. Understanding the operational dynamics of these antennas is crucial for designing an efficient telecommunication network within electrical machines. Therefore, this paper revisits the fundamental properties of antennas to evaluate how various components of electrical machines affect their operation patterns. By doing so, we seek to optimize communication system performance and propose an optimal design framework. The unique challenges posed by the geometric constraints, limited space and material composition of electrical machines remain underexplored. To address these challenges, we utilize a rotor temperature monitoring system (RTMS), which employs wireless radio frequency transmission to monitor the machine's rotor temperature during operation [8]. Enhancing the direct communication quality of RTMS has involved implementing various telecommunications techniques, including radiofrequency characterization. The importance of RTMS cannot be overstated, as failures in electrical machines can lead to significant disruptions in production lines, affecting costs, quality, and safety [9; 10]. Ensuring the efficient operation of these machines is paramount [11; 12]. Wireless communication offers a promising approach for real-time monitoring of electrical machines, particularly in detecting faults when parameters deviate from their normal ranges [13]. However, integrating wireless communication into the control of electrical machines presents several challenges, including electromagnetic compatibility issues among devices [14]. These challenges stem from factors such as device geometry, confined spaces, and the materials used in electrical machine components, as well as the electromagnetic flux within rotating machines and the presence of electromagnetic fields from rotating modules. Our previous research highlighted that low-frequency flux within machines does not interfere with high-frequency transmitters. Experimental findings from radio monitoring systems within rotating electrical machines revealed significant fluctuations in received power and rapid fading of the wireless channel due to transmitter rotation. Additionally, a slight reduction in signal amplitude was noted when the emitter was positioned within the electric machine [15].