ISSN : 1796-203X
Volume : 1    Issue : 1    Date : April 2006

A Novel Pulse Echo Correlation Tool for Transmission Path Testing and Fault Diagnosis
David M. Horan and Richard A. Guinee
Page(s): 31-39
Full Text:
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In this paper a novel pulse sequence testing methodology is presented [22] as an alternative to
Time Domain Reflectometry (TDR) for transmission line health condition monitoring, faultfinding
and location. This scheme uses Pseudo Random Binary Sequence (PRBS) injection for
transmission line testing and fault location with cross correlation (CCR) techniques to build a
unique response profile, as a characteristic signature, to identify the type of fault, if any, or load
termination present as well as its distance from the point of stimulus insertion. This fault
characterization strategy can be applied to a number of industrial application scenarios embracing
high frequency (HF) printed circuit board (PCB) and integrated circuit (IC) device operation, overhead
lines and underground cables in inaccessible locations, which rely on a transmission line pathway
or via common to all cases either for signal propagation or power conveyance.
As an improved time-domain methodology PRBS enabled fault finding can be performed online at
low amplitude levels for normal uncorrelated signal traffic disturbance rejection and to average out
the presence of transmission link extraneous noise pickup over several PRBS cycles for the
purpose of multiple fault coverage, resolution and identification. This unique troubleshooting tool is
due to the perturbation of the transmission line with a special pseudonoise (pN) sequence of
uncorrelated pulses of random polarity and the subsequent CCR measurement of their aggregate
response at the test node input for line fault identification and localisation.
Based on the distinct spike-like attribute of the PRBS autocorrelation (ACR) function, a pre-location
fault measurement relies on the relative time displacement of the device/system conditioned PRBS
cross-correlated echo response from the ACR peak for accurate fault/load location and
identification. This measured time translation of the correlation peaks can be subsequently used to
determine the propagation delay of the reflected response from the fault/load-termination of the unit
under test (UUT). This procedure not only results in fault/load parameter identification but also of the
reflection transit time from the fault interface and thus the distance of the fault from the point of
stimulus insertion.
In this paper a lumped parameter circuit model is presented to emulate generalized transmission
line, using the wellknown pSpice simulation package, for a range of known loadterminations
mimicking fault conditions in a range of application scenarios encountered in practice. Numerous
line behavioural simulations for various fault conditions, known apriori, with measured CCR
response demonstrate the capability of and establishes confidence in the effectiveness of the
PRBS test method in fault type identification and location. The accuracy of the method is further
validated through theoretical calculation using known lumped parameters, fault termination
conditions and link distance in transmission line simulation.

Index Terms
Transmission Path Testing, Fault Testing, Fault Identification, BIST, PRBS, Correlation Function