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Parasitic Line Detection

IP.com Disclosure Number: IPCOM000042632D
Original Publication Date: 1984-Jun-01
Included in the Prior Art Database: 2005-Feb-04

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Chisam, GF [+details]


A parasitic line or stub on a printed circuit net can be detected by applying a frequency spectrum through parallel paths, one being the circuit net under test and the other through a delay filter, then detecting and differentiating the phase difference of the signals from the two paths, and displaying the result on an oscilloscope. Referring to the figure, a frequency generator 1, of wide band width, is connected to a power splitter 2 that has one output connected to the circuit line 3 under test and the other output as an input to an all-pass filter 4 serving as a group delay. Circuit line 3 and filter 4 are connected to phase detector 5. Any differences in phase due to transmission delays in line 3 are differentiated at 6 and the results displayed on oscilloscope 7.