Testing of transmitters for communication links by software simulation of reference channel and/or reference receiver

1. A computer-implemented method for testing a transmitter for a communications link, the method comprising a non-transitory processor executing software instructions to effect the steps of:

accessing a stored waveform for the transmitter under test, wherein the stored waveform is based on capture of an output generated by the transmitter in response to a data test pattern applied to the transmitter; and

calculating a performance metric for the transmitter under test, wherein the performance metric is a difference between (a) SNR for reception by an ideal communications receiver and (b) SNR for a test communications link comprising the transmitter under test, a reference channel and a reference receiver, the reference receiver including an equalizer, the performance metric calculated based on simulated propagation of the waveform through the reference receiver.

2. The method of claim 1 , wherein the reference channel comprises a microwave channel.

3. The method of claim 1 , wherein the reference channel comprises a radio frequency channel.

4. The method of claim 1 , wherein the reference channel comprises an optical channel.

5. The method of claim 1 , wherein the reference channel comprises a cable.

6. The method of claim 1 wherein the equalizer includes a finite length equalizer.

7. The method of claim 1 wherein the equalizer includes an infinite length equalizer.

8. The method of claim 1 wherein the equalizer is not physically realizable in hardware.

9. The method of claim 1 wherein the step of calculating the performance metric comprises:

for each of a plurality of different reference channels, calculating a channel-specific performance metric, wherein the channel-specific performance metric is a difference between (a) SNR for reception by an ideal communications receiver and (b) SNR for a channel-specific test communications link comprising the transmitter under test, that specific reference channel and a reference receiver, the performance metric calculated based on simulated propagation of the waveform through the reference receiver; and

determining the performance metric for the transmitter based on the channel-specific performance metrics.

10. The method of claim 9 wherein the step of determining the performance metric for the transmitter based on the channel-specific performance metrics comprises:

selecting the worst channel-specific performance metric as the performance metric for the transmitter.

11. The method of claim 1 further comprising:

accessing the data test pattern, wherein the step of calculating the performance metric includes use of the data test pattern.

12. The method of claim 1 wherein the step of calculating the performance metric utilizes a baseline of the captured waveform.

13. The method of claim 12 further comprising:

using the captured waveform to compute the baseline.

14. The method of claim 1 wherein the reference receiver includes an equalizer with a slicer, and the SNR for the test communications link is measured at an input to the slicer.

15. The method of claim 1 wherein the performance metric is based on compliance with a standard applicable to the transmitter.

16. The method of claim 1 further comprising:

applying the data test pattern to the transmitter under test;

capturing the output generated by the transmitter in response to the applied data test pattern; and

storing the waveform based on the captured output.

17. A computer-implemented method for testing a transmitter for a communications link, the method comprising a non-transitory processor executing software instructions to effect the steps of:

accessing a stored waveform for the transmitter under test, wherein the stored waveform is based on capture of an output generated by the transmitter in response to a data test pattern applied to the transmitter; and

calculating a performance metric for the transmitter under test, wherein the performance metric is a difference between (a) SNR for an ideal communications link, the ideal communications link including an ideal transmitter and an ideal channel that outputs a distortion-free version of a waveform based on the data test pattern and an ideal matched filter receiver; and (b) SNR for a test communications link comprising the transmitter under test, a reference channel and a reference receiver, the reference receiver including a decision feedback equalizer having a feedforward filter and a feedback filter and a slicer, the SNR for the test communications link measured at an input to the slicer; the performance metric calculated based on simulated propagation of the waveform through the reference receiver.

18. The method of claim 17 , wherein the ideal channel comprises a microwave channel.

19. The method of claim 17 , wherein the ideal channel comprises a radio frequency channel.

20. The method of claim 17 , wherein the ideal channel comprises an optical channel.

21. The method of claim 17 wherein the step of calculating the performance metric comprises:

for each of a plurality of different reference channels, calculating a channel-specific performance metric, wherein the channel-specific performance metric is a difference between (a) SNR for reception by an ideal communications receiver and (b) SNR for a channel-specific test communications link comprising the transmitter under test, that specific reference channel and a reference receiver, the performance metric calculated based on simulated propagation of the waveform through the reference receiver; and

determining the performance metric for the transmitter based on the channel-specific performance metrics.