Apparatus for and method of cable diagnostics utilizing time domain reflectometry

1. A method of performing diagnostics on a channel including a cable using circuitry embedded in a communications transceiver without the need to use special cable measurement equipment, said method comprising the steps of:

generating, in said communications transceiver, a programmed pulse based on a dynamic channel impulse response of said channel, wherein said pulse may be positive or negative;

transmitting said pulse from one end of said cable;

receiving a reflected signal and generating a plurality of sequences of samples therefrom;

ignoring an initial sequences of samples;

detecting and measuring the amplitude of positive and negative peaks present in said reflected signal;

determining diagnostic information about said cable based on the location and amplitude of said positive and negative peaks; and

identifying a topology for said cable.

2. The method according to claim 1 , wherein the width of said pulse is programmable.

3. The method according to claim 1 , wherein the width of said pulse is one symbol wide for better diagnostic accuracy with shorter lengths of cable.

4. The method according to claim 1 , wherein the width of said pulse is five symbols wide for better diagnostic accuracy with longer lengths of cable.

5. The method according to claim 1 , wherein a peak is identified only if both its positive and negative portions are detected.

6. The method according to claim 1 , wherein said positive peak is declared for a sample if the absolute value of the sample exceeds a low threshold, the sample is positive, the sample is larger than a previous number of samples and the sample is larger than a number of subsequent samples.

7. The method according to claim 1 , wherein said negative peak is declared for a sample if the absolute value of the sample exceeds a low threshold, the sample is negative, the sample is smaller than a previous number of samples and the sample is smaller than a number of subsequent samples.

8. The method according to claim 1 , wherein said step of detecting of peaks comprises the step of declaring an unmatched peak if in a sufficient number of samples following a first peak, a second peak having a sign opposite that of said first peak and smaller absolute value is found and ignored.

9. The method according to claim 1 , wherein said step of detecting of peaks comprises the step of declaring a matched peak if following a first peak, a second peak having a sign opposite that of said first peak and smaller absolute value is found and ignored.

10. The method according to claim 1 , further comprising the step of declaring an open or shorted cable if a peak is identified that exceeds a high threshold.

11. The method according to claim 1 , further comprising the step of ignoring peaks having a sign opposite that of a previously identified peak.

12. The method according to claim 1 , wherein said step of determining comprises generating cable length as a function of peak location and amplitude information.

13. The method according to claim 1 , wherein said step of determining comprises the step of locating one or more impedance mismatches existing along said cable.

14. The method according to claim 1 , further comprising the step of performing generating, receiving and detecting several times and averaging corresponding samples.

15. The method according to claim 1 , wherein the step of generating comprises the step of generating a plurality of pulses, each having different lengths.

16. An apparatus embedded in a communications transceiver, said apparatus for performing cable diagnostics on a channel including a, comprising:

a pulse generator coupled to said channel, said pulse generator operative to program a pulse based on a dynamic channel impulse response of said channel which is transmitted onto said cable;

a peak detector coupled to said cable and operative to detect and measure the amplitude of positive and negative peaks present in a reflected signal;

a memory coupled to said peak detector for storing peak location and amplitude information; and

means for determining diagnostic information about said cable based on the location and amplitude of said positive and negative peaks.

17. An apparatus embedded in a communications transceiver, said apparatus for performing cable diagnostics on a channel including a cable, said apparatus comprising:

means for generating in said communications transceiver a programmed pulse based on a dynamic channel impulse response of said channel, wherein said pulse is transmitted from one end of said cable;

means for receiving a reflected signal and generating a sequence of samples therefrom;

means for detecting and measuring the amplitude of positive and negative peaks present in said reflected signal; and

means for determining diagnostic information about said cable based on the location and amplitude of said positive and negative peaks.

18. A communications transceiver having an embedded time domain reflectometry (TDR) diagnostic module and coupled to a channel including a cable, said transceiver comprising:

a pulse generator coupled to said channel, said pulse generator operative to program a pulse based on a dynamic channel impulse response of said channel;

a transmitter to transmit said pulse onto said cable;

a receiver for receiving a reflected signal;

a peak detector coupled to said cable and operative to detect and measure the amplitude of positive and negative peaks present in said reflected signal;

a memory coupled to said peak detector for storing peak location and amplitude information; and

means foe determining diagnostic information about said cable based on the location and amplitude of said positive and negative peaks.