Method and apparatus for estimating cable length
View Patent ↗A method for estimating cable length includes steps of generating a detection signal to a cable, wherein the detection signal includes a first pulse and a second pulse with opposite voltages in sequence; receiving a refection signal of the detection signal from the cable; and determining length of the cable according to a superposed waveform of the detection signal and the refection signal.
1. A method for estimating a length of a cable, the method comprising:
generating a detection signal to the cable, the detection signal comprising a first pulse and a second pulse with opposite voltage directions in sequence;
receiving a refection signal of the detection signal from the cable; and
determining the length of the cable according to a superposed waveform of the detection signal and the refection signal.
2. The method of claim 1 , wherein the first pulse is a positive voltage pulse, and the second pulse is a negative voltage pulse.
3. The method of claim 2 , wherein a pulse width of the second pulse is less than a pulse width of the first pulse.
4. The method of claim 1 , wherein the detection signal meets a link pulse template in an Ethernet standard.
5. The method of claim 4 , wherein amplitude of the second pulse approximates to a minimum voltage of the link pulse template.
6. The method of claim 1 , wherein the step of determining the length of the cable according to the superposed waveform of the detection signal and the refection signal comprises:
determining the length of the cable is shorter than a first particular value when the superposed waveform has a third pulse following the detection signal, wherein the third pulse is a refection signal of the second pulse.
7. The method of claim 6 , wherein amplitude of the third pulse is greater than a threshold value.
8. The method of claim 1 , wherein the step of determining the length of the cable according to the superposed waveform of the detection signal and the refection signal comprises:
determining the length of the cable is between a first particular value and a second particular value when a pulse width of the second pulse in the superposed waveform increases.
9. The method of claim 1 , wherein a pulse width of the second pulse provides one sampling point up to four sampling points at an Ethernet operating frequency.
10. The method of claim 1 further comprising:
determining the length of cable according to a travel time of the reflection signal.
11. An estimation device for estimating a length of a cable, the estimation device comprising:
a signal generator for generating a detection signal to the cable, the detection signal comprising a first pulse and a second pulse with opposite voltage directions in sequence;
a switching unit, coupled to the signal generator, for receiving a refection signal of the detection signal from the cable; and
an estimation unit, coupled to the switching unit, for determining the length of the cable according to a superposed waveform of the detection signal and the refection signal.
12. The estimation device of claim 11 , wherein the first pulse is a positive voltage pulse, and the second pulse is a negative voltage pulse.
13. The estimation device of claim 12 , a pulse width of the second pulse is less than a pulse width of the first pulse.
14. The estimation device of claim 11 , wherein the detection signal meets a link pulse template in an Ethernet standard.
15. The estimation device of claim 14 , wherein amplitude of the second pulse approximates to a minimum voltage of the link pulse template.
16. The estimation device of claim 11 , wherein the estimation unit comprises:
a first detection unit for detecting whether the superposed waveform has a third pulse following the detection signal, wherein the third pulse is a refection signal of the second pulse;
a second detection unit for detecting whether a pulse width of the second pulse in the superposed waveform increases; and
a determination unit for determining the length of the cable according to detection results of the first detection unit and the second detection unit.
17. The estimation device of claim 16 , wherein the determination unit determines the length of the cable is shorter than a first particular value when the superposed waveform has the third pulse following the detection signal.
18. The estimation device of claim 17 , wherein amplitude of the third pulse is greater than a threshold value.
19. The estimation device of claim 16 , wherein the determination unit determines the length of the cable is between a first particular vale and a second particular value when the pulse width of the second pulse in the superposed waveform increases.
20. The estimation device of claim 11 , wherein a pulse width of the second pulse provides one sampling point up to four sampling points at an Ethernet operating frequency.
21. The estimation device of claim 11 , wherein the estimation unit is further utilized for determining the length of cable according to a travel time of the reflection signal.