This paper investigates the influence of frequency-dependent soil conductivity and permittivity on narrowband and broadband power line communication (PLC) channel modeling using transmission line theory. For narrowband PLC channels, the variation of the transfer function H(f) of a single overhead wire over a finitely conducting ground due to frequency-dependent soil parameters is minimal for low-resistivity soils, but more relevant for high-resistivity soils in the upper frequency range. For broadband PLC channels, H(f) strongly depends on the soil model for frequencies below 10MHz or so, but is relatively insensitive to this parameter at higher frequencies. The average channel attenuation is more affected by soil model and soil parameters than the achievable data rate. Also, the voltage definition assumed in the derivation of the per-unit-length parameters of the line has little influence on the results. A comparison between different formulations traditionally used in PLC channel modeling indicates that the admittance associated with a finitely conducting ground should not be neglected in the modeling of broadband PLC channels.
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