Transmitter tuning using receiver gradient
A controller operates to adjust a transmitter to optimize transmission of a communications signal. The controller measures properties of a signal received from a transmitter, and generates a figure of merit (FOM) for the signal. The FOM is compared against a record of previous FOMs and corresponding previous transmitter tap values, the transmitter tap value indicating settings of a transmitter equalizer of the transmitter during transmission of the signal. A differential between the FOM and a plurality of the previous FOMs is determined, and, in response to the differential being positive, a subsequent tap value is selected from a subset of potential tap values. The subsequent tap value is sent to the transmitter for adjustment of the transmitter equalizer.
1. A circuit, comprising:
a receiver configured to receive a signal from a transmitter;
a monitor configured to measure properties of the signal and generate a figure of merit (FOM) for the signal, the FOM indicating a measure of signal-to-noise;
a controller configured to:
compare the FOM against a record of previous FOMs and corresponding previous transmitter tap values, the transmitter tap value indicating settings of a transmitter equalizer of the transmitter during transmission of the signal;
determine a differential between the FOM and a plurality of the previous FOMs; and
in response to the differential being positive, select a subsequent tap value from a subset of potential tap values; and
an interface configured to send the subsequent tap value to the transmitter for adjustment of the transmitter equalizer.
2. The circuit of claim 1 , wherein the controller is further configured to generate the record based on previous adjustment and measurement of the signal.
3. The circuit of claim 1 , wherein the subset of potential tap values each provide a transmit signal amplitude that is substantially the same across the potential tap values.
4. The circuit of claim 1 , wherein the subset of potential tap values excludes tap values associated with a signal amplitude that is substantially lower or higher than a signal amplitude associated with the tap value.
5. The circuit of claim 1 , wherein the controller is further configured to calculate an average FOM from the plurality of previous FOMs, the differential being relative to the average FOM.
6. The circuit of claim 1 , wherein the controller is further configured to determine whether the tap value is a final tap value.
7. The circuit of claim 6 , wherein the controller determines the final tap value in response to the differential being below the threshold.
8. The circuit of claim 6 , wherein the controller determines the final tap value in response to detecting that the FOM and a plurality of the previous FOMs are within a threshold range.
9. The circuit of claim 6 , wherein the controller determines the final tap value based on a match between the tap value and the previous tap values, the match indicating a repetition among tap values.
10. The circuit of claim 6 , wherein the controller determines the final tap value in response to a timer surpassing a threshold value.
11. The circuit of claim 6 , wherein the controller determines the final tap value in response to detecting the FOM being above a signal quality threshold.
12. The circuit of claim 1 , wherein the controller is further configured to detect an adverse move based on the FOM indicating a decrease in signal-to-noise relative to the previous FOMs.
13. The circuit of claim 12 , wherein the controller is further configured to select the subsequent tap value to reverse the decrease in signal-to-noise.
14. The circuit of claim 1 , wherein the controller is further configured to adjust the receiver equalizer tap coefficients, linear equalizer response, and voltage gain based on the FOM indicating an increase or decrease in signal-to-noise relative to the previous FOMs.
15. A method, comprising:
receiving a signal from a transmitter;
measuring properties of the signal and generate a figure of merit (FOM) for the signal, the FOM indicating a measure of signal-to-noise;
comparing the FOM against a record of previous FOMs and corresponding previous transmitter tap values, the transmitter tap value indicating settings of a transmitter equalizer of the transmitter during transmission of the signal;
determining a differential between the FOM and a plurality of the previous FOMs;
in response to the differential being positive, select a subsequent tap value from a subset of potential tap values; and
sending the subsequent tap value to the transmitter for adjustment of the transmitter equalizer.
16. The method of claim 15 , further comprising generating the record based on previous adjustment and measurement of the signal.
17. The method of claim 15 , wherein the subset of potential tap values each provide a transmit signal amplitude that is substantially the same across the potential tap values.
18. The method of claim 15 , wherein the subset of potential tap values excludes tap values associated with a signal amplitude that is substantially lower or higher than a signal amplitude associated with the tap value.
19. The method of claim 15 , further comprising calculating an average FOM from the plurality of previous FOMs, the differential being relative to the average FOM.
20. The method of claim 15 , further comprising determining whether the tap value is a final tap value.
21. The method of claim 15 , further comprising determining the final tap value in response to the differential being below the threshold.