| Title |
Phase-Sweep-Based Complex Signal Estimation for Improving Signal Detection Performance in Time-Frequency Domain Reflectometry |
| Authors |
이주봉(Ju-Bong Lee) ; 권구영(Gu-Young Kwon) ; 이춘권(Chun-Kwon Lee) |
| DOI |
https://doi.org/10.5370/KIEE.2026.75.8.1872 |
| Keywords |
Analytic signal; Complex signal estimation; Phase sweep; Submarine cable diagnosis; Time-frequency domain reflectometry |
| Abstract |
Reflectometry-based cable diagnosis is used to detect impedance discontinuities and estimate fault locations in submarine and power cables. Among various reflectometry methods, time-frequency domain reflectometry (TFDR) evaluates the similarity between incident and reflected signals in the time-frequency domain. In conventional TFDR, real-valued measured signals are converted into analytic signals using the Hilbert transform before Wigner-Ville distribution (WVD) and time-frequency cross correlation (TFCC) analysis. However, for Gaussian-enveloped linear chirp (GELC) signals, the Hilbert-transform-based analytic signal may include approximation errors due to nonstationary AM-FM characteristics, finite-length FFT implementation, spectral leakage, and approximate Bedrosian conditions. These errors can distort the WVD representation and degrade TFCC-based detection reliability. In this paper, a phase-sweep-based complex signal estimation method is applied to improve TFDR detection performance. Multiple real-valued responses acquired with different initial phases are modeled using cosine and sine components, and the complex response is estimated using least squares. Experimental results show that the proposed method reduces out-of-band WVD energy leakage and increases TFCC similarity coefficients at factory joint locations. The results demonstrate that phase-sweep-based complex signal estimation can improve weak reflection detection in TFDR-based cable diagnosis. |