Receiver Managing Pre-Cursor ISI via Adaptive Sampling
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional receivers face challenges in effectively removing pre-cursor intersymbol interference (ISI) in multilevel signals, particularly when using a Mueller-Muller phase detector, which can lead to noise vulnerability and unstable clock data recovery, making it difficult to maintain a stable vertical eye margin.
Innovation Solution
A receiver design that includes a sampling circuit, clock controller, and control circuit to control the ratio of the main cursor's magnitude to the pre-cursor ISI's magnitude, using a decision feedback equalizer and adaptive threshold voltages to manage the sampling clock signal and phase detection, ensuring the receiver maintains a stable operation and sufficient eye margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a Mueller-Muller phase detector is used to reduce power consumption by sampling once per UI, then power consumption is reduced, but the receiver becomes vulnerable to noise and the locking point drifts
Solution Approach 1:
The patent implements dynamic sampling by adjusting the sampling clock frequency based on signal conditions. The sampling circuit can operate at different rates - once per UI for power savings when conditions permit, or at higher rates when noise or ISI conditions require more frequent sampling for reliable detection
Solution Approach 2:
The system dynamically changes operational parameters including sampling frequency and threshold voltages based on detected signal conditions. The control circuit adjusts these parameters to optimize between power consumption and detection reliability, switching between operational modes as needed
2Object-generated harmful factors
If adaptive equalizer is used to remove pre-cursor ISI, then ISI reduction is achieved, but vertical eye margin cannot be guaranteed in multilevel signals
Solution Approach 1:
The patent applies preliminary equalization to remove pre-cursor ISI before the main detection process. By pre-processing the signal to eliminate anticipated interference from previous symbols, the system prepares the signal for more reliable threshold comparison and sampling
Solution Approach 2:
The patent introduces an intermediary processing stage between the input signal and the phase detector. This intermediate equalization stage acts as a mediator that conditions the signal by removing pre-cursor ISI, making the subsequent detection process more reliable for multilevel signals
3Productivity
If multilevel signal processing is implemented to increase bandwidth, then bandwidth is increased, but amplitude differences between main cursor values become smaller making the signal more affected by ISI
Solution Approach 1:
The patent applies preliminary equalization to counteract the increased ISI susceptibility before detection. By removing pre-cursor ISI in advance, the system compensates for the reduced amplitude margins inherent in multilevel signaling, allowing high-bandwidth operation without sacrificing reliability
Data Source
AI summary
A receiver includes a sampling circuit configured to sample a comparison result between an input signal and a plurality of threshold voltages according to a sampling clock signal; a clock controller configured to generate the sampling clock signal according to a clock control signal; and a control circuit configure to generate the clock control signal and the plurality of threshold voltages according to a target value and an output of the sampling circuit. The control circuit operates to control a ratio of a magnitude of a main cursor of the input signal and a magnitude of a pre-cursor intersymbol interference to be the target value.