Detection Sensitivity Improvement in Sequence Time Domain Reflectometry by Removing Pulse Reflected at Nodes in Bus Network

Since the sequence time domain reflection can reduce the influence of background noise by cross-correlating the transmitted and reflected pulses, our motivation lies in its use for anomaly detection in bus networks. The problems here are that not only is the pulse amplitude reduced when traveling over a node in a bus network, but also the reflected pulse modulated by M-sequence from the node causes a reduction in detection sensitivity. Therefore, by making the pulse cross-correlated with the transmitted pulse not just a reflected pulse but the difference between the reflected pulses during normal and anomaly statuses, the effect of reflected pulses generated at the nodes can be removed and the sensitivity of anomaly detection can be improved. When a 20 pF capacitive anomaly exists on a line with a characteristic impedance of 120 $\Omega$, applying the method with a series length K=63 and a symbol length $T_{\mathrm{c}}$=10 ns of sinusoidal pulses, the anomaly detection sensitivity after the second node improved from 0.10 to 0.53 without background noise. Furthermore, it was found that the anomaly detection sensitivity could be improved even in the presence of additive white Gaussian noise.