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Each subsequent pulse represents other potential paths which are longer than the shortest path.
In order to observe main path response of surface filter (SAW), other responses can be filtered by gate function to observe frequency
response of the main path only.
8.5.4.
Fault Location by the Use of Low Pass Mode
The measured piece response of time domain reflectometer (TDR) can be simulated by the use of real part format and such
response includes definite discontinuous type of information which is very useful. Figure below provides the low pass response in the
format of known discontinuous real part, and each discontinuous circuit has corresponding time domain S
11
response waveform.
Measure can be performed by the use of low pass step or low pass impulse mode; however, it is easier to distinguish discontinuous
types by the use of low pass step mode, which is similar to Measure with conventional time domain reflectometer (TDR).
Fig.
8
-17 Low Pass Time Domain Response Waveform of Discontinuous Circuit
8.5.5.
Reflection Measure in Low Pass Mode
Horizontal axis data:
It represents the time used when pulse is transmitted from measuring port and transferred to discontinuous point and then gets
back to measuring port.
Vertical axis data:
In real part format, it represents reflection coefficient (ρ).
Example below is the Measure result of the same reflection by the use of both low pass impulse and low pass step modes:
Fi.
8
-18 Reflection Measure in Low Pass Mode
Example below provides Measure results of two different cables in real part format and low pass response includes physical location
and impedance type information of the discontinuous points.
