Reflectometer with echo canceller

Abstract

Various embodiments are directed to a zero-echo canceling system adapted to at least partially cancel a received zero-echo by calculating an error signal as a difference between the zero-echo and a zero-echo canceling signal.

1 . A method of reducing a zero-echo comprising: 
 combining a zero-echo canceling signal based on a transmitted pulse with a received zero-echo to reduce the received zero-echo; and    calculating an error signal as a difference between the zero-echo and the zero-echo canceling signal.    
   
   
       2 . The method of  claim 1 , further comprising adjusting the zero-echo canceling signal based on the error signal to decrease the error signal and decrease the received zero-echo.  
   
   
       3 . The method of  claim 2 , wherein adjusting comprises adjusting a value of a voltage bridge or a variable resistor.  
   
   
       4 . The method of  claim 1 , wherein the zero-echo has been sufficiently cancelled or attenuated based on the combining to allow a full-path reflection to be detected.  
   
   
       5 . The method of  claim 1 , wherein the zero-echo comprises a short path reflection of the transmitted pulse.  
   
   
       6 . An apparatus comprising: 
 a zero-echo canceller to combine a zero-echo canceling signal based on a transmitted pulse with a received zero-echo to reduce the received zero-echo and to calculate an error signal as a difference between the zero-echo and the zero-echo canceling signal.    
   
   
       7 . The apparatus of  claim 6 , said zero-echo canceller to adjust the zero-echo canceling signal based on the error signal to decrease the error signal and decrease the received zero-echo.  
   
   
       8 . The apparatus of  claim 7 , further comprising at least one of a voltage bridge and a variable resistor to adjust.  
   
   
       9 . The apparatus of  claim 6 , said zero-echo canceller to generate the zero-echo canceling signal.  
   
   
       10 . The apparatus of  claim 6 , said zero-echo canceller coupled to a combining circuit and a voltage divider, the combining circuit adapted to combine a zero-echo received from the voltage divider and a zero-echo canceling signal received from the zero-echo canceller.  
   
   
       11 . The apparatus of  claim 10 , the combining circuit comprising an adder.  
   
   
       12 . The apparatus of  claim 10 , the combining circuit comprising a subtraction circuit.  
   
   
       13 . The apparatus of  claim 10 , the zero-echo canceller comprising a variable voltage divider.  
   
   
       14 . The apparatus of  claim 13 , the variable voltage divider comprising a variable resistor.  
   
   
       15 . A system comprising: 
 a transceiver coupled to a DSL line to be tested;    a zero-echo canceller coupled to said transceiver, said zero-echo canceller to combine a zero-echo canceling signal based on a transmitted pulse with a received zero-echo to reduce the received zero-echo and to calculate an error signal as a difference between the zero-echo and the zero-echo canceling signal.    
   
   
       16 . The system of  claim 15 , said zero-echo canceller to adjust the zero-echo canceling signal based on the error signal to decrease the error signal and decrease the received zero-echo.  
   
   
       17 . The system of  claim 16 , further comprising at least one of a voltage bridge and a variable resistor to adjust.  
   
   
       18 . The system of  claim 15 , said zero-echo canceller to generate the zero-echo canceling signal.  
   
   
       19 . The system of  claim 15 , said zero-echo canceller coupled to a combining circuit and a voltage divider, the combining circuit adapted to combine a zero-echo received from the voltage divider and a zero-echo canceling signal received from the zero-echo canceller.  
   
   
       20 . The system of  claim 15 , the zero-echo canceller comprising a variable voltage divider.