Adaptive Receiver Precursor Cancelation for ISI Equalization
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Solution Overview
Problem
Current high-speed interface designs face challenges in effectively canceling inter-symbol interference (ISI), particularly precursor ISI, which degrades signal quality and complicates adaptation within receiver circuits due to lack of channel response information from the transmitter.
Innovation Solution
The proposed solution involves a data receiver circuit with a summer circuit combining input and feedback signals to generate an equalized signal, a clock generator circuit for clock recovery, and precursor and post-cursor compensation circuits to mitigate ISI effects, using voltage offsets and samples to adapt and generate feedback signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional receiver circuits are used without precursor cancelation, then the circuit complexity is lower, but the signal quality deteriorates due to uncancelled precursor ISI
Solution Approach 1:
The equalization function is segmented into two independent parts: precursor cancelation circuit and post-cursor equalization circuit. The precursor cancelation circuit specifically targets and removes precursor ISI using separate tap weights, while the post-cursor equalization circuit handles remaining distortion. This segmentation allows each circuit to be optimized for its specific function, improving overall signal quality without requiring a completely complex redesign of the entire equalization system.
Solution Approach 2:
The precursor cancelation circuit acts as an intermediary component between the input signal and the post-cursor equalization circuit. It processes the input signal first to remove precursor ISI, then passes the cleaned signal to the post-cursor equalization circuit. This intermediary approach allows the system to handle precursor and post-cursor interference through separate, specialized circuits rather than requiring a single complex equalizer.
2Reliability
If adaptive equalization is implemented to improve signal quality, then the signal quality improves, but the adaptation capability is limited due to lack of channel response information from transmitter
Solution Approach 1:
Instead of having the transmitter send channel response information to the receiver (conventional approach), this invention inverts the approach by having the receiver independently estimate and adapt to channel characteristics through its own precursor cancelation and post-cursor equalization circuits. The receiver adapts its tap weights based on local signal analysis rather than relying on transmitter-provided channel information, enabling adaptation without additional overhead or transmitter involvement.
Solution Approach 2:
The receiver circuit performs self-adaptation by independently estimating channel characteristics and adjusting its own equalization parameters. The precursor cancelation circuit and post-cursor equalization circuit work together to automatically adapt to channel conditions using only the received signal, without requiring external channel response information from the transmitter. This self-service capability enables the system to maintain signal quality across varying channel conditions.
3Reliability
If both precursor and post-cursor ISI are cancelled using a single equalization circuit, then the signal quality improves, but the device complexity increases significantly
Solution Approach 1:
The equalization function is divided into two separate circuits: precursor cancelation circuit with its own tap weights and post-cursor equalization circuit with separate tap weights. Each circuit is optimized for its specific function and can be independently adapted and controlled. This segmentation reduces the complexity of any single circuit while maintaining the combined capability to handle both precursor and post-cursor ISI effectively.
Solution Approach 2:
The precursor cancelation circuit serves as an intermediary that processes the input signal before it enters the post-cursor equalization circuit. By removing precursor ISI in advance, it simplifies the task of the post-cursor equalization circuit, allowing it to focus only on post-cursor distortion. This staged approach reduces the overall complexity compared to a single circuit attempting to handle all types of ISI simultaneously.
Data Source
AI summary
A data receiver circuit includes a summer circuit configured to receive an input signal that encodes multiple data symbols, and combine the input signal with a feedback signal to generate an equalized input signal, which is used to generate a clock signal. The data receiver circuit also includes multiple data slicer circuits that sample, using the clock signal and multiple voltage offsets, the equalized input signal to generate multiple samples of a particular data symbol. A precursor compensation circuit included in the data receiver circuit may generate an output value for the particular data symbol using the multiple samples. The data receiver circuit also includes a post cursor compensation circuit that generates the feedback signal using at least one of the multiple samples and a value of a previously received sample.