Coupling circuit design for Single-Wire Earth Return PLC applications through cascaded s-parameters optimization

This paper proposes a coupling circuit design technique for Powerline Carrier (PLC) applications in Medium-Voltage (MV) overhead networks. A case study for a PLC targeting a Single Wire Earth Return (SWER) network coupling via a 5.1-nF Coupling Capacitor (CC) exemplifies the need for this research. The proposed method relies on the construction of an s -parameter cascade for the load, source, and matching circuit for the PLC application. The s -parameter object for the load is modeled using the load's access impedance, which consists of the capacitance of an 11-m coaxial cable, a 5.1-nF rated CC with a drain coil of 0.223 mH, and the 480 Ω characteristic impedance of the line. The source s -parameter object is dependent on the source impedance, as well as the magnetizing reactance of the source transformer. Finally, an LC ladder circuit is used for the s -parameter characterization of the matching circuit. The proposed optimization method shows excellent virtue in converging to the global optimum, independent of the starting values of a five-element prototype network. The proposed method has been applied to different cost functions and different levels of target mean error. Laboratory and field tests validate the proposed method's effectiveness in enhancing signal transmission over SWER networks. The optimized coupling circuit achieved a 2.21 dB increase in Signal-to-Noise Ratio (SNR), equating to a 67.8% improvement in signal power. Additionally, the circuit effectively attenuated high-frequency noise, including AM radio interference, significantly improving the reliability of PLC communication in MV networks. This technique can be easily and time efficiently applied in various applications and for testing different coupler configurations. • Developed an optimization method for coupling circuits in SWER PLC systems. • Enabled efficient coupling circuit design using cascaded S-parameters. • Proposed a systematic optimization to minimize insertion loss (80–330 kHz). • Verified performance via lab tests and real-world SWER trials. • Mitigated AM radio noise in field, improving PLC signal robustness.