Signal Loss Detector Using DFE Pattern Recognition
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Solution Overview
Problem
High-speed data communication systems face challenges in reliably detecting signal loss due to inter-symbol interference, which can lead to false loss-of-signal detection if the detection threshold of analog envelope detectors is set too high.
Innovation Solution
A signal loss detector is implemented in a receiver using a decision feedback equalizer (DFE) with multiplexed decision paths, which monitors decisions for specific patterns indicative of signal absence and asserts loss-of-signal detection, thereby reducing false positives.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an analog envelope detector is used to detect signal magnitude, then loss-of-signal detection is achieved, but false loss-of-signal detection occurs when the detection threshold is set too high
Solution Approach 1:
The patent replaces the analog envelope detector with a digital pattern detection mechanism. Instead of using analog signal magnitude detection with threshold comparison, the system uses digital logic to detect specific bit patterns (such as alternating 101010 or 010101 sequences) that are characteristic of loss-of-signal conditions. This substitution of analog detection with digital pattern recognition eliminates the false detection problem associated with threshold setting while maintaining reliable loss-of-signal detection.
2Measurement precision
If the detection threshold of the envelope detector is lowered to reduce false positives, then detection sensitivity improves, but detection reliability deteriorates due to noise and interference
Solution Approach 1:
The patent employs feedback equalization using a decision feedback equalizer (DFE) that processes the received signal and generates decisions about signal presence. The DFE uses feedback from previously detected bits to compensate for inter-symbol interference, allowing the system to maintain high detection sensitivity without suffering from false positives due to noise. The feedback mechanism enables reliable pattern detection even in noisy environments by continuously adjusting the equalization based on detected signal characteristics.
3Speed
If high-speed data communication is implemented, then communication speed increases, but inter-symbol interference worsens making signal loss detection more difficult
Solution Approach 1:
The patent applies feed-forward equalization (FFE) in the transmitter as a preliminary action to pre-compensate for inter-symbol interference before the signal is transmitted through the channel. By equalizing the signal in advance, the system reduces the impact of ISI at the receiver end, enabling reliable pattern-based loss-of-signal detection even at high communication speeds where ISI would otherwise be severe.
Data Source
AI summary
In an example, an apparatus for detecting signal loss on a serial communication channel coupled to a receiver includes an input, a detector, and an output circuit. The input is configured to receive decisions generated by sampling the serial communication channel using multiplexed decision paths in a decision feedback equalizer (DFE). The detector is coupled to the input and configured to monitor the decisions for at least one pattern generated by the multiplexed decision paths in response to absence of a serial data signal on the serial communication channel. The output circuit is coupled to the detector and configured to assert loss-of-signal in response detection of the at least one pattern by the detector.