Patent ID: 6534996
Filing Date: 2003-03-18
Classification: H04M

Abstract:
A test logic circuit in a digital subscriber line (DSL) modem configured to perform time domain reflectometry (TDR) measurements on a transmission line, the test logic circuit comprising:means for preparing the transmission line for the TDR measurements; means for creating a predetermined test signal; means for transmitting the predetermined test signal to the transmission line at a predetermined repetition rate; means for receiving reflected signals; means for accumulating the received reflected signals; means for measuring a time interval between transmission of the test signals and reception of the reflected signals; means for identifying the location of disruptions from the measured time intervals; means for deconvolving known effects of the DSL modem from the accumulated signal to produce a deconvolved signal; means for determining changes in shape between the transmitted test signal and the deconvolved signal; means for determining changes in phase between the transmitted test signal and the deconvolved signal; and means for deriving an impedance profile of the transmission line from the differences in the shape and phase between the test signal and the deconvolved signal.