Adaptive Receiver Pre-Cursor Cancellation 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 hampers communication channel performance 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, clock generator circuit, data slicer circuit, precursor compensation circuit, and post-cursor compensation circuit, which combine input signals with feedback signals to generate equalized signals, sample data symbols using voltage offsets, and adapt clock recovery by generating output values and feedback signals using samples and previously received data symbols.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional equalization methods are used, then post-cursor ISI can be compensated, but precursor ISI cannot be effectively canceled due to lack of channel response information
Solution Approach 1:
The transmitter performs preliminary channel characterization by transmitting known test sequences and calculating channel response information before actual data transmission. This pre-computed channel response is then used by the receiver to effectively cancel both precursor and post-cursor ISI, resolving the contradiction between reliability and adaptability.
Solution Approach 2:
Channel response information acts as an intermediary between the transmitter and receiver. The transmitter computes this information and transmits it to the receiver, enabling the receiver to perform accurate equalization without needing to perform its own channel characterization, thus achieving both reliability and adaptability.
2Adaptability or versatility
If complex adaptation mechanisms are added to the receiver, then channel response information can be obtained, but circuit complexity increases significantly
Solution Approach 1:
The transmitter performs the channel characterization function that would otherwise require complex receiver circuitry. By having the transmitter compute and provide channel response information, the receiver avoids implementing complex adaptation mechanisms while still achieving accurate equalization.
Solution Approach 2:
The channel response information serves as an intermediary that transfers adaptation capability from the transmitter to the receiver without requiring complex receiver circuitry. This mediator enables the receiver to achieve adaptability through simple lookup and application of pre-computed values.
3Measurement precision
If multiple voltage offsets are used for sampling, then data recovery accuracy improves, but power consumption and circuit complexity increase
Solution Approach 1:
Instead of using an excessive number of voltage offsets for sampling, the system uses a limited set of offsets combined with precise timing control and channel response-based equalization. This partial action approach achieves high measurement precision without the proportional increase in power consumption that would result from using many more offsets.
Solution Approach 2:
The system replaces the mechanical approach of using multiple voltage offsets for sampling with a computational approach using channel response information and timing adjustment. This substitution reduces power consumption while maintaining or improving measurement precision through digital signal processing rather than extensive analog voltage switching.
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.