Compensating transmission line to reduce sensitivity of performance due to channel length variation
Described embodiments provide a method and system for signal compensation in a SERDES communication system that includes monitoring the quality of a data signal after passing through a transmission channel. The quality of the data signal is monitored with at least one of a BER calculation algorithm and a received eye quality monitoring algorithm. Variations in channel length of the transmission channel are compensated for by i) adjusting a length of transmission line delay of the data signal from the transmission channel, ii) comparing the data signal quality with a threshold for the adjusted data signal; and iii) repeating i) and ii) until the data signal quality meets the threshold.
1. A method of signal compensation in a SERDES communication system comprising:
a) monitoring a quality of a data signal after passing through a transmission channel with at least one of a BER calculation algorithm and a received eye quality monitoring algorithm;
b) compensating for channel length variations of the transmission channel by the steps of
i) adjusting a length of transmission line delay of the data signal from the transmission channel;
ii) comparing the data signal quality with a threshold for the adjusted data signal; and
iii) repeating steps i) and ii) until the data signal quality meets the threshold.
2. The invention as recited in claim 1 , wherein the step b1) adjusts the length of transmission line delay by the step of configuring switches adapted to provide intermediate tap points between a plurality of transmission line segments, each transmission line segment providing a corresponding portion of the length of transmission line delay.
3. The invention as recited in claim 2 , wherein the step b1) adjusts the length of transmission line delay based on BER from the BER calculation algorithm.
4. The invention as recited in claim 2 , wherein the step b1) adjusts the length of transmission line delay based on eye characteristics from the received eye quality monitoring algorithm.
5. The invention as recited in claim 2 , wherein the length of transmission line delay is substantially equal to a fraction of the baud period of a serial data rate of the SERDES communication system.
6. An apparatus for compensating for transmission channel length variations in a SERDES communication system, comprising:
a) a plurality of transmission line segments;
b) a plurality of switches adapted to provide intermediate tap points between each of the plurality of transmission line segments;
c) a plurality of switches adapted to disconnect non-selected transmission line segments from the selected transmission line segments and the selected intermediate tap point; and
d) a feedback circuit to monitor a signal quality of received data, wherein each of the plurality of selectable transmission line segments introduces a corresponding delay in a transmission path of the received data.
7. The invention as recited in claim 6 , wherein one or more of the plurality of switches are digitally controlled.
8. The invention as recited in claim 7 , wherein the feedback circuit adaptively adjusts the configuration of the switches to provide a desired BER.
9. The invention as recited in claim 6 , wherein the feedback circuit is an eye monitor adapted to implement a received eye quality monitoring algorithm.
10. The invention as recited in claim 6 , wherein a total delay introduced by the plurality of transmission line segments is substantially equal to a fraction of the baud period of the serial data rate of the SERDES communication system.
11. The invention as recited in claim 6 , wherein the transmission line segments are substantially equal in length to one another.
12. The invention as recited in claim 6 , wherein elements of the plurality of transmission line segments are arranged in a rectangular pattern to reduce physical distance between each of the plurality of tap points and an input terminal of a receiver.
13. The invention as recited in claim 6 , wherein elements of the plurality of transmission line segments are arranged in a circular pattern to reduce physical distance between each of the plurality of tap points and an input terminal of a receiver.
14. The invention as recited in claim 6 , wherein the apparatus is embodied in an integrated circuit of a SERDES receiver.
15. The invention as recited in claim 6 , wherein the signal quality monitored by the feedback circuit is at least one of a BER and a received data eye shape.
16. A machine-readable medium, having encoded thereon program code, wherein, when the program code is executed by a machine, the machine implements a method for signal compensation in a SERDES communication system, comprising the steps of:
a) monitoring a quality of a data signal after passing through a transmission channel with at least one of a BER calculation algorithm and a received eye quality monitoring algorithm;
b) compensating for channel length variations of the transmission channel by the steps of
i) adjusting a length of transmission line delay of the data signal from the transmission channel;
ii) comparing the data signal quality with a threshold for the adjusted data signal; and
iii) repeating steps i) and ii) until the data signal quality meets the threshold.
17. The invention as recited in claim 16 , wherein the step b1) adjusts the length of transmission line delay by the step of configuring switches adapted to provide intermediate tap points between a plurality of transmission line segments, each transmission line segment providing a corresponding portion of the length of transmission line delay.
18. The invention as recited in claim 17 , wherein the step b1) adjusts the length of transmission line delay based on BER generated by the BER calculation algorithm.
19. The invention as recited in claim 17 , wherein the step b1) adjusts the length of transmission line delay based on eye characteristics from the received eye quality monitoring algorithm.
20. The invention as recited in claim 17 , wherein the length of transmission line delay is substantially equal to a fraction of the baud period of a serial data rate of the SERDES communication system.