Location attempt of a coaxial cable with multiple abnormalities by frequency domain reflectometry

We have demonstrated that frequency domain reflectometry (FDR) can locate the position of degradation or abnormality in a cable with the assistance of inverse fast-Fourier transform (IFFT). Although it is easily understandable that this FDR-IFFT method can be applied for a location attempt of a cable with more than one abnormality, we have not demonstrated this experimentally. Therefore, we heated two different positions on a coaxial cable of 31.5 m insulated with low-density polyethylene using two heating chambers. As a result, it is clearly indicated that the two positions can be located if we heated there only by 10°C. Furthermore, this method can precisely estimate the length of a heated portion in a coaxial cable when we set the highest measurement frequency higher than 600 MHz.