SerDes High-Cut Equalization for Reflective Short PCB Traces
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Solution Overview
Problem
High-rate SerDes blocks designed with standard channel assumptions and parameter limits exhibit inadequate performance on low-loss channels due to significant impedance mismatches and reflection-induced inter-symbol interference (ISI), which conventional equalization techniques fail to adequately address.
Innovation Solution
Implementing a serializer and deserializer with a pre-equalizer that attenuates frequency components at half the symbol rate relative to one third, and a controller that adjusts equalizer coefficients or bandwidth to artificially suppress high-frequency components based on channel reflection strength, thereby improving equalization performance on low-loss channels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional high-pass filter equalization techniques are used, then high-frequency signal components are boosted to combat channel loss, but reflection-induced inter-symbol interference is amplified on low-loss channels
Solution Approach 1:
The patent inverts the conventional equalization approach by using a high-cut filter instead of a high-pass filter. Rather than boosting high-frequency components to combat channel loss, the invention attenuates high-frequency components to suppress reflection-induced ISI, thereby resolving the contradiction between improving equalization performance and reducing harmful reflections on low-loss channels
Solution Approach 2:
The patent changes the equalization parameter from high-pass filtering to high-cut filtering by adjusting the transfer function characteristics. This parameter change allows the system to adapt to low-loss channel conditions where reflection suppression is more critical than loss compensation, thereby resolving the technical contradiction
2Adaptability or versatility
If standard SerDes design parameters are used, then the system operates correctly on typical channels, but performance degrades on short low-loss channels with impedance mismatches
Solution Approach 1:
The patent introduces dynamic adaptability by making the equalizer transfer function可调 (adjustable) based on channel characteristics. The system can dynamically switch between conventional high-pass filtering for typical channels and high-cut filtering for low-loss channels, thereby achieving both broad channel compatibility and optimized performance on specific channel types
Solution Approach 2:
The patent enables parameter changes in the equalizer transfer function to adapt to different channel conditions. By modifying the filtering characteristics from high-pass to high-cut based on channel loss measurements, the system achieves versatility across different channel types while maintaining low bit error ratios on challenging low-loss channels
Data Source
AI summary
An illustrative short, high-rate communications link includes a serializer that provides a signal having a symbol rate of at least 10 GHz; and a deserializer that receives the signal via a printed circuit board (“PCB”) trace coupled to the serializer with a first impedance mismatch and coupled to the deserializer with a second impedance mismatch. At least one of the serializer and deserializer includes an equalizer that attenuates a frequency component of the signal at half of the symbol rate relative to a frequency component of the signal at one third of the symbol rate. Though such attenuation may reduce signal-to-noise ratio, an improved communications performance may nevertheless be achieved by suppression of signal reflections.