AGC Adaptation Circuit With Dynamic Step Size for Fast Receiver Convergence
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Solution Overview
Problem
As data rates increase, communication channels become susceptible to frequency-dependent signal loss and noise, making it challenging for receivers to adapt quickly and effectively using automatic gain control (AGC) and decision feedback equalizers to improve bit error rate (BER) performance.
Innovation Solution
A circuit and method that dynamically adjust the AGC adaptation step size based on observed values and target values, using modulo operations and lookup tables, to improve convergence time and stability of the AGC and equalizer adaptation loops, allowing for either fixed or variable step sizes for AGC and equalizer loops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the data rate is increased to meet demand for higher data throughput, then the data throughput is improved, but the signal becomes more susceptible to corruption by frequency-dependent signal loss and noise
Solution Approach 1:
The patent implements feedback loops in both the AGC circuit and equalizer circuit that continuously monitor signal quality metrics (such as eye height or signal power) and automatically adjust circuit parameters to compensate for channel loss and noise. The AGC feedback loop adjusts gain based on observed signal levels, while the equalizer feedback loop adjusts tap coefficients based on error signals, enabling the system to maintain signal quality despite increased data rates and channel impairments.
2Reliability
If the receiver adaptation time is extended to improve BER performance, then the bit error rate is improved, but the timing requirements for high speed communication protocols are not met
Solution Approach 1:
The patent employs dynamic adaptation step sizes that adjust based on the current convergence state of the adaptation loops. The AGC circuit uses a dynamic gain adjustment step size that is larger when the signal is far from the target level and smaller when close to convergence. Similarly, the equalizer uses dynamic tap coefficient adjustment step sizes. This dynamic approach allows rapid initial convergence while ensuring precise final settling, meeting both speed and accuracy requirements.
Solution Approach 2:
The patent changes the adaptation parameters (step sizes) based on the observed signal conditions and convergence progress. The AGC adaptation step size is modified based on the difference between observed and target signal levels, and the equalizer adaptation step size is modified based on error signals and convergence criteria. These parameter changes enable the system to adapt quickly during transient conditions while maintaining stability during steady-state operation.
3Device complexity
If a fixed adaptation step size is used in the AGC circuit, then the circuit complexity is reduced, but the convergence time and stability of the adaptation loop are degraded
Solution Approach 1:
The patent implements variable adaptation step sizes in the AGC circuit that change based on the convergence state. The step size is dynamically adjusted based on the difference between the observed signal level and the target level, allowing larger adjustments when far from convergence and smaller adjustments when close to the target. This parameter change approach maintains relatively simple circuit architecture while significantly improving convergence speed and stability compared to fixed step size methods.
Data Source
AI summary
A circuit includes an AGC adaptation circuit configured to receive a first signal generated based on an AGC output signal from an AGC circuit. The AGC circuit applies an AGC gain to an AGC input signal to generate the AGC output signal. The AGC adaptation circuit determines an observed value of the first signal, and determines a AGC adaptation step size based on the observed value and a predetermined target value associated with the first signal. The AGC adaptation circuit provides a second signal to adjust the AGC gain of the AGC circuit using the AGC adaptation step size.