Transmitter Equalizer Tap Extraction via Waveform Comparison
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Solution Overview
Problem
In high-speed digital communication systems like PCIE Gen6, the high frequency nature makes accurate measurement of single Unit Interval pulse heights impractical, leading to challenges in extracting transmitter equalizer tap values due to significant impairments such as inter-symbol interference.
Innovation Solution
The method involves capturing waveforms with and without the transmitter equalizer turned on, using an oscilloscope or similar device, and then processing these waveforms to extract the equalizer taps without requiring knowledge of the digital pattern. This is achieved by minimizing the mean squared error between measured and reconstructed step response waveforms, or by using short Fast Fourier Transform to analyze the spectrums of the waveforms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If single UI pulse height measurement is used, then extraction process is simple, but measurement accuracy deteriorates due to inter-symbol interference at high frequencies
Solution Approach 1:
The patent applies preliminary action by capturing waveforms before the equalizer is enabled, then using these pre-captured waveforms as a baseline to subsequently extract equalizer tap values when the equalizer is enabled. This preliminary waveform capture allows the system to separate the equalizer's contribution from the total signal, avoiding the need for direct high-frequency pulse measurements that suffer from inter-symbol interference.
2Measurement precision
If pattern detection method is used to extract equalizer taps, then accuracy can be maintained, but system complexity and processing time increase
Solution Approach 1:
The patent extracts only the necessary information (waveform data) without requiring full pattern detection. By capturing waveforms with and without the equalizer enabled and comparing these extracted waveforms, the system obtains equalizer tap values without the complexity of detecting and analyzing complete digital patterns, thus reducing system complexity while maintaining accuracy.
3Measurement precision
If pattern detection method is used, then equalizer tap extraction accuracy is maintained, but processing time increases
Solution Approach 1:
The patent applies partial action by performing only the necessary waveform capture and comparison operations without executing the full pattern detection process. The system captures waveforms with and without the equalizer enabled, then uses a simplified comparison method to extract tap values, achieving sufficient accuracy without the time-consuming complete pattern detection workflow.
Data Source
AI summary
A test and measurement instrument has one or more input ports to connect the instrument to a device under test (DUT), one or more processors configured to execute code to cause the one or more processors to: receive an equalized waveform and an un-equalized waveform through the input port from the DUT, without any knowledge of a digital pattern that corresponds to the waveforms and without extracting the digital pattern from the waveforms, align the un-equalized waveform and the equalized waveform in time to produce an aligned un-equalized waveform and an aligned equalized waveform, and use the aligned equalized waveform and the aligned un-equalized waveform to determine equalizer tap values.