Modeling and Research of Measurement Network for Return Loss on LEU

The lineside electronic unit (LEU) serves as the critical interface device for communication between the balise transmission system (BTS) and external systems in modern railway signaling infrastructure. Its transmission performance directly affects the reliable operation of switched balises, which are essential components for train control and safety systems. Any degradation in transmission characteristics can lead to communication failures, potentially compromising railway safety and operational efficiency. In order to study the transmission characteristics about the interface C of LEU, this paper proposes a comprehensive return loss network model based on the lumped-element method for transmission lines. This innovative modeling approach addresses the complex impedance matching challenges encountered in real-world railway applications. The model utilizes transmission line theory to establish a detailed two-port cascaded network between LEU and balise, taking into account the electrical properties of interconnecting cables and their impact on signal integrity. Comprehensive simulations are performed on a network model of an LEU connected to cables of varying lengths, ranging from short connections to extended cable runs typical in railway installations. The simulation results are systematically compared with experimental measurements obtained from actual LEU systems. The results indicate that the simulation results are in excellent agreement with the experimental.