| Power line (PL) channel characteristic have a significant impact on many facets of communication system such as the choice of modulation scheme, design of error detection and correction, network scheme and so on. And the knowledge of PL channel characteristic is basic for designing high rate power line communication (PLC) system. Combining the scientific technology project granted by Chongqing municipal commission of education, PL channel characteristic is studied in the paper. The main work is as follows:1. Measurement system of PL channel characteristic is designed, and the characteristic of noise, transmission and impedance are analyzed based on the measuring result.2. The equivalence between symmetrical three-pole cable and two-conductor transmission line (TL) is derived, as well as the condition for holding. Then associating the particular wiring and grounding practices, paper proposes that cable analysis is ought to be based either on two-conductor TL model or on three-conductor TL model in light of the specific power grid.3. Aiming at the problem of the ratio method cited in the paper and incorporating the principle of two-current-probe method, a novel impedance measurement method, system identification, is proposed.4. The analysis of measurement results shows, noise originates complexly, of which narrowband interference varies distinctly with day and night, whereas the fluctuation of background noise is small; channel fading has frequency selective characteristic and forward transmission characteristic is identical to backward transmission under certain conditions; the absolute value of impedance in frequency domain fluctuates very obviously and varies with time very fast, whereas impedance phase varies slow.5. Noise models in time domain and frequency are studied, and transmission characteristic models are categorized into top-down and bottom-up model, time-domain and frequency-domain model, concrete model and statistical model.
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