Electronic circuit and method for testing a line

1. An electronic circuit for testing a subscriber line comprising:

a signal generator comprising a pseudo-random bit series (PRBS) generator for generating a spread spectrum test signal;

a coupler for coupling the signal generator to the line, for transmitting test signal on said line, and for receiving a reflected signal generated on said line when said test signal is transmitted; and

an evaluating unit connected to said coupler for receiving from said coupler the reflected signal, said evaluating unit comprising:

an adjustable delay unit for adjustably delaying said test signal;

a digital to analog (D/A) converter for converting said delay test signal into an analog delayed test signal;

a mixer for multiplying the delayed analog test signal with the reflected signal;

an integrator for integrating the output signal of said mixer in order to generate a correlation function of said test signal and said reflected signal; and

a processor for receiving and evaluating the generated correlation function.

2. The electronic circuit according to claim 1 , wherein the coupler is a directional coupler.

3. The electronic circuit according to claim 1 , further comprising:

a reset line connected to at least one of the PRBS generator, the integrator, and/or a analog to digital (A/D) converter which converts the output of the PRBS generator to an analog signal before it is input to the coupler; thereby controlling the generation of correlation values which comprise a measurement sequence.

4. The electronic circuit according to claim 1 , wherein the coupler is a line hybrid coupler.

5. The electronic circuit according to claim 1 , further comprising:

a digital to analog (D/A) converter for converting the spread spectrum text signal into an analog signal before it is input to the coupler.

6. The electronic circuit according to claim 1 , further comprising:

an analog to digital (A/D) converter for converting the output of the integrator into a digital signal before it is input to the processor.

7. The electronic circuit according to claim 1 , wherein the subscriber line comprises a Digital Subscriber Line (DSL).

8. An electronic circuit for testing a subscriber line comprising:

a signal generator comprising a random bit series generating means for generating a digital spread spectrum test signal;

a coupler for coupling the signal generator to the line, for transmitting said test signal on said line, and for receiving a reflected signal generated on the line when the test signal is transmitted; and

an evaluating unit connected to said coupler for receiving from said coupler the reflected signal, and for calculating and evaluating the correlation function of said test signal and said reflected signal, said evaluating unit comprising:

an analog to digital (A/D) converter for converting the reflected analog signal received from said coupler into a digital signal; and

a processor for calculating the correlation function of the digital spread spectrum test signal as output by said signal generator and said digitized reflected signal.

9. The electronic circuit according to claim 8 , wherein the random bit generating means is a pseudo random bit series (PRBS) generator.

10. The electronic circuit according to claim 8 , wherein the coupler is a directional coupler.

11. The electronic circuit according to claim 8 , wherein the coupler is a line hybrid coupler.

12. The electronic circuit according to claim 8 , wherein the subscriber line comprises a Digital Subscriber Line (DSL).

13. The electric circuit according to claim 8 , further comprising:

a digital to analog (D/A) converter for converting the spread spectrum text signal into an analog signal before it in input to the coupler.

14. The electronic circuit according to claim 13 , further comprising:

an analog to digital (A/D) converter for converting the analog spread spectrum text signal output the D/A converter into a digital signal before it is input to the processor.

15. The electronic circuit according to claim 8 , wherein the coupler comprises:

two parallel branches, each comprising a series connection of impedances, wherein the test signal is input to said coupler in parallel to said branches, and wherein the reflected signal is received between two connecting points, one of said two connecting points being located on a connection between two of the impedances connected in series in one parallel branch, and the other connecting point being located on a connection between two of the impedances connected in series in the other parallel branch; and

a transformer connecting the line to the coupler wherein the input impedance of said transformer comprises the load of said line and the output impedance comprises one of said impedances in one of said two parallel branches.

16. An electronic circuit for testing a subscriber line comprising:

a signal generator comprising a random bit series generating means for generating a digital spread spectrum test signal;

a coupler for coupling the signal generator to the line, for transmitting said test signal on said line, and or receiving a reflected signal generated on the line when the test signal is transmitted, the coupler comprising:

two parallel branches, each comprises a series connection of impedances, wherein the test signal is input to said coupler in parallel to said branches, and wherein the reflected signal is received between two connecting points one of said two connecting points being located on a connection between two of the impedances connected in series in one parallel branch, and the other connecting point being located on a connection between two of the impedances connected in series in the other parallel branch; and

a transformer connecting the line to the coupler wherein the input impedance of said transformer comprises the load of said line and the output impedance comprises one of said impedances in one of said two parallel branches; and

an evaluating unit connected to said coupler for receiving from said coupler the reflected signal, and for calculating and evaluating the correlation function of said test signal and said reflected signal.

17. The electronic circuit according to claim 16 , wherein the random bit generating means is a pseudo random bit series (PRBS) generator.

18. The electronic circuit according to claim 17 , wherein said evaluating means further comprises:

an adjustable delay unit for adjustably delaying the spread spectrum test signal as generated by said PRBS generator;

a digital to analog (D/A) converter for converting said delayed test signal into an analog signal;

a mixer for multiplying the delayed analog test signal with the reflected signal; and

an integrator for integrating the output signal of said mixer in order to generate a correlation function of said test signal and said reflected signal.

19. The electronic circuit according to claim 18 , further comprising:

a processor for receiving and evaluating the generated correlation function.

20. The electronic circuit according to claim 16 , wherein the subscriber line comprises a Digital Subscriber Line (DSL).

21. The electronic circuit according to claim 16 , further comprising:

a digital to analog (D/A) converter for converting the spread spectrum text signal into an analog signal before it is input to the coupler.

22. A method for testing a subscriber line, comprising the steps of:

generating a spread spectrum test signal with a random bit series generating means;

transmitting, via a coupler, said test signal on said line;

receiving by said coupler, a reflected signal generated on said line when the test signal is transmitted;

selectively delaying the test signal directly output from the generating means;

converting the delayed test signal into an analog signal;

mixing the delayed analog test signal with the reflected signal;

integrating the output of the mixing step in order to generate a correlation function of said test signal and said reflected signal; and

evaluating the correlation function of said test signal and said reflected signal.

23. The method according to claim 22 , wherein the coupler is a directional coupler.

24. The method according to claim 22 , wherein the coupler is a line hybrid coupler.

25. The method according to claim 22 , further comprising the step of:

resetting at least one of the PRBS generator, the integrator, and/or a analog to digital (A/D) converter which converts the output of the PRBS generator to an analog signal before it is input to the coupler, thereby controlling the generation of correlation values which comprise a measurement sequence.

26. The method according to claim 22 , further comprising the step of:

converting the spread spectrum text signal into an analog signal before it is input to the coupler.

27. The method according to claim 22 , further comprising the step of:

converting the output of the integrating step into a digital signal before the evaluating step.

28. The method according to claim 22 , wherein the subscriber line comprises a Digital Subscriber Line (DSL).

29. A method for testing a subscriber line comprising the steps of:

generating a spread spectrum test signal with a random bit series generating means;

transmitting, via a coupler, said test signal on said line;

receiving, by said coupler, a reflected signal generated on said line when the test signal is transmitted;

converting the reflected signal from the coupler into a digital signal;

receiving, by a processor, the digitized signal and the test signal;

calculating, by a processor, the correlation function of the digitized reflected signal and said test signal; and

evaluating, by the processor, the calculated correlation function.

30. The method according to clam 29 , wherein the random bit generating means is a pseudo random bit series (PRBS) generator.

31. The method according to claim 29 , wherein the coupler is a directional coupler.

32. The method according to claim 29 , wherein the coupler is a line hybrid coupler.

33. The method according to claim 29 , wherein the subscriber line comprises a Digital Subscriber Line (DSL).

34. The method according to claim 29 , further comprising:

converting the spread spectrum text signal into an analog signal before it is input to the coupler.

35. The method acceding to claim 34 , further comprising the steps of:

converting the analog spread spectrum text signal into a digital signal before it is input to the processor.

36. The method according to claim 29 ,

wherein the step of transmitting, by the coupler, the test signal comprises the step of:

receiving, by the coupler, the test signal in parallel to two parallel branches, each branch comprising a series connection of impedances; and

wherein the step of receiving, by the coupler, the reflected signal comprises the step of:

receiving, by the coupler, the reflected signal between two connecting points, one of said two connecting points being located on a connection between two of the impedances connected in series in one parallel branch, and the other connecting point being located on a connection between two of the impedances connected in series in the other parallel branch.

37. The method according to claim 36 , wherein a transformer connects the line to the coupler wherein the input impedance of said transformer comprises the load of said line and the output impedance comprises one of said impedances in one of said two parallel branches.

38. A method for testing a subscriber line comprising the steps of:

generating a spread spectrum test signal with a random bit series generating means;

receiving, by a coupler, the test signal in parallel to two parallel branches, each branch comprising a series connection of impedances, and transmitting said test signal on said line;

receiving, by said coupler, a reflected signal generated on said line when the test signal is transmitted, wherein the reflected signal is received between two connecting points, one of said two connecting points being located on a connection between two of the, impedances connect in series in one parallel branch, and the other connecting point being located on a connection between two of the impedances connected in series in the other parallel branch;

receiving, by an evaluation unit, the reflected signal from the coupler;

receiving, by the evaluating unit, the test signal from the random bit series generating means;

calculating, by the evaluating unit, the correlation function of the reflected signal and said test signal; and

evaluating, by the evaluating unit, the calculated correlation function.

39. The method according to claim 38 , wherein the random bit generating means is a pseudo random bit series (PRBS) generator.

40. The method according to claim 38 , wherein the step of calculating by the evaluating unit, the correlation function of the reflected signal and said test signal comprises the steps of:

selectively delaying the received test signal;

converting the delayed test signal into an analog signal;

mixing the delayed analog test signal with the received reflected signal; and

integrating the output of the mixing step in order to generate a correlation function of said test signal and said reflected signal.

41. The method according to claim 38 , wherein the subscriber line comprises a Digital Subscriber Line (DSL).

42. The method according to claim 38 , further comprising:

converting the spread spectrum text signal into an analog signal before it is input to the coupler.