Spread-Spectrum Time-Domain Reflectometer Method Based On Chaotic Sequences

Cable faults'detection and location has been identified as a widespread concern at home and abroad. One of the most difficult and challenging problem is intermittent faults that occurred in a very short duration, usually a few milliseconds and cannot be replicated on the ground. In order to detect and locate intermittent faults, we can only apply online continuous testing methods. Firstly, this paper describes some traditional test methods on intermittent faults detection and location, and metrs of these methods. Then it focuses on Spread-Spectrum Time-Domain Reflectometer (SSTDR) method based on chaotic sequences. So far, pseudo-random sequence (PN sequence) which is modulated by a sine wave signal has been widely used as the SSTDR test signal. We can locate the point of failure by detecting the cross correlation between the reflected signal and the test signal. The low test signal levels and high noise immunity of this test method make it well suited to test for intermittent faults. However, due to a number of deficiencies of PN sequences and increasingly widely use of chaotic sequences in spread-spectrum communication, making chaotic sequences replace the PN sequences in spread-spectrum time-domain reflectometry method to be possible. This paper studies SSTDR testing methods based on chaotic sequences, mainly on the feasibility of the application of chaotic sequences in SSTDR. Then, gives an instance(in RS485 communication) where chaotic sequences and PN sequences work as the test codes respectively. Also, this paper analyzes the influence on detection due to chaotic sequences'parameters. Through simulation analysis, it can be seen that the results of detection and location can be better than the case when PN sequences work as the test signal, the use of chaotic sequences as the test signal is feasible and efficient.