Reconstructing Rx Waveforms from Mid-Channel Probes
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Solution Overview
Problem
In high-speed I/O design, existing methods struggle to accurately measure waveforms at the receiver-end of a channel due to corruption by reflections, especially when physical access is limited, requiring a technique to account for reflections based on measurements taken near the middle of the channel.
Innovation Solution
A method and apparatus that use linear network analysis and signal processing to derive the waveform at the receiver-end by creating a filtered function or equation, utilizing s-parameters from simulated models and load impedance to recreate the waveform uncorrupted by reflections, with a computer-controlled approach to generate channel models and calculate the Rx waveform.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If de-embedding is used to mathematically remove channel components, then measurement accuracy at receiver-end is improved, but physical access to receiver-end is required which is not available in many cases
Solution Approach 1:
The patent uses an intermediary probe point located between the transmitter and receiver to perform measurements. This intermediate location provides physical accessibility while still enabling the derivation of receiver-end waveform characteristics through mathematical processing that accounts for the channel segment between the probe point and receiver.
Solution Approach 2:
The patent replaces the mechanical requirement of physical probing at the receiver-end with a mathematical system that processes measurements taken at an accessible intermediate point. By using de-embedding techniques and signal processing algorithms, the physical measurement constraint is substituted with computational analysis.
2Ease of operation
If probing is performed near the middle of the channel, then physical accessibility is improved, but measurement accuracy deteriorates due to reflection corruption
Solution Approach 1:
The patent converts the harmful effect of reflections into useful information. By deliberately accounting for and modeling the reflection phenomena that occur at the intermediate probe point, the system can mathematically eliminate their corrupting influence and recover the true receiver-end waveform, thereby transforming the measurement challenge into a solvable problem.
Solution Approach 2:
The patent changes the parameters used to describe the channel by introducing S-parameters (scattering parameters) that characterize the channel segments. This parameter transformation enables the mathematical separation of different signal components including reflections, allowing accurate reconstruction of the receiver-end waveform from intermediate measurements.
3Measurement precision
If channel reflections are accounted for using complex mathematical models, then waveform reconstruction accuracy is improved, but system complexity increases
Solution Approach 1:
The patent segments the channel into distinct sections: the segment from transmitter to probe point and the segment from probe point to receiver. Each segment is characterized separately using S-parameters, allowing the complex overall channel to be broken down into manageable components that can be processed independently and then combined to achieve accurate waveform reconstruction.
Data Source
AI summary
Embodiments of the present invention reconstruct a waveform at a receiver-end of a channel from an observed waveform physically measured at a probe point near the middle of the channel, where the channel is corrupted by reflections. The channel may be a memory channel of a high-speed I/O interface, for example. Equations to derive the waveform may be created using linear network analysis and/or signal processing, for example. S-parameters may be derived from simulated models representing components from the probe point to the load. The s-parameters together with the load impedance are used to recreate the desired waveform free from corruption due to reflections.