| 摘要 |
A fault on a nonloaded telephone subscriber loop is sectionalized by a frequency domain distance detection system. The derivative with respect to frequency of the phase angle of the complex input impedance of a cable pair is continuously monitored over a swept-frequency range beyond the voice-frequency band. The phase itself is obtained indirectly as the Hilbert transform of the logarithmic differences between the instantaneous impedance and a delayed version thereof. Thus, circuitry which is less sensitive to noise, parameter variation, and measurement error than prior techniques becomes practical for generating waves having energy peaks corresponding to the distance from the measurement end of a loop under test to impedance irregularities therealong.
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