研究目的
To demonstrate that the combination of frequency domain reflectometry and inverse fast Fourier transform can detect degradation or abnormality in a polymer-insulated electric cable even if it occurs uniformly over the entire cable length.
研究成果
The FDR-IFFT method can detect abnormalities in a cable even if they occur over the entire length of the cable, as long as they change the cable's characteristic impedance. This was demonstrated by detecting temperature changes over the entire length of an LDPE-insulated coaxial cable.
研究不足
The method's effectiveness is limited by the propagation properties of high-frequency electromagnetic waves, which attenuate more at higher frequencies. The highest frequency that can be used is limited by these attenuation effects.
1：Experimental Design and Method Selection:
The FDR-IFFT method was used, which combines frequency domain reflectometry and inverse fast Fourier transform to locate degradation or abnormality in a cable.
2：Sample Selection and Data Sources:
A coaxial cable insulated with low-density polyethylene (LDPE) with a length of 30 m was used. The entire length of the cable was heated to 60 and 90 °C in a temperature-controlled chamber.
3：List of Experimental Equipment and Materials:
A network analyzer (E5061B, Agilent) was used to inject sinusoidal electromagnetic waves and record reflected waveforms.
4：Experimental Procedures and Operational Workflow:
The cable was connected to the network analyzer, which conducted IFFT analyses on the reflected waveforms.
5：Data Analysis Methods:
The time-domain spectra obtained from the IFFT analyses were used to detect changes in the cable's characteristic impedance.
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