# Passive Power Line Communication Filter Design and Benchmarking Using Scattering Parameters
###### Abstract  
NB-PLC (narrowband power line communication) is a method of data communication that involves superimposing a relatively high-frequency signal (9 kHz to 500 kHz), which contains data, onto the power grid's low frequency (50 to 60 Hz) signal. While using the existing power grid as a transmission medium is convenient, the power grid was not designed for this purpose, leading to challenges such as conducted emissions and infrastructure limitations. To overcome these technical challenges, passive filters are necessary. This article presents the design, simulation (using scattering parameters), and evaluation of an NB-PLC filter by comparing it to commercially available filters. Our proposed design and benchmarking methods enable the accurate prediction of the filter's behavior in field conditions. After comparing our filter with commercially available filters, we observed that it exhibits superior characteristics. Specifically, our filter has the best insertion loss versus frequency, achieved three times higher attenuation at 50 kHz (\(-\)130 dB) compared to the best commercially available filter (\(-\)40 dB), and has a power consumption of 0.6 W, which is comparable to the most power-efficient commercial filter (0.5 W). Additionally, our filter has the second best input and output impedance of 3.6 \(\Omega\) within the frequency range of 35-95 kHz. power line communication (PLC); power grid; NB-PLC; smart grid; filters; conducted disturbances +
Footnote †: journal: Applied  
Mains connected switched-mode power supplies and inverters commonly utilize switching frequencies below 150 kHz, resulting in the generation of conducted emissions that impact NB-PLC [15,19]. The selection of switching frequencies below 150 kHz is motivated by several key factors [20]:  
* Efficiency: lower switching frequencies can improve the overall efficiency of the SMPS. At lower frequencies, the switching losses in the power semiconductors, such as transistors or diodes, are reduced. This results in lower power dissipation and higher conversion efficiency;
* Electromagnetic interference (EMI): higher switching frequencies can generate more emissions due to increased harmonics and faster switching transitions. Relaxed or an absence of limits below 150 kHz contribute to this choice as well;
* Thermal management: switching components in SMPS can generate heat and operating at lower frequencies can help manage thermal issues. With reduced switching frequency, the components have more time to dissipate heat between each switching cycle;
* Component selection: some components used in SMPS, such as inductors and transformers, may have limitations at higher frequencies, including increased losses and size constraints. The growing adoption of NB-PLC within smart grid applications, combined with existing standardization gaps and the presence of grid-connected devices that operate at switching frequencies below 150 kHz, necessitates the development of power line filters capable of providing significant attenuation within the Cenelec bands A, B, C, and D.  
Passive filters were used for a long time [21, 22, 23, 24] as a means of addressing conducted emissions in the power grid or to isolate different sections of a PLC network [25]. This article aims to contribute to this field of expertise by addressing several novel aspects. Firstly, it serves as a comprehensive source of information for designing and testing narrowband NB-PLC filters. Through an extensive literature review, it provides a complete understanding of the development, integration, and testing considerations associated with NB-PLC filters. In addition, this research introduces a new approach by employing S-parameters (scattering parameters) for the design and simulation of NB-PLC filters. While the use of S-parameters in design and simulation methods is not unprecedented [26, 27], this study represents the first instance of applying this specific approach to NB-PLC filter design.