Adaptive Equalizer Coefficient Switching for Asynchronous Sampling
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Solution Overview
Problem
Existing adaptive equalizers require synchronous clocks, which are difficult to maintain due to issues like inter-code crosstalk, chromatic dispersion, and polarization mode dispersion, making it challenging to effectively track time-varying input signals and correct spectral aberrations in communications systems.
Innovation Solution
An adaptive equalizer system that includes a monitoring device to control coefficient updates based on the down sampling phase of input or equalized signals, allowing for adaptive equalization under asynchronous clock conditions without the need for a clock recovery circuit, by using a switching unit to manage coefficient updates based on phase detection and predetermined thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a synchronous clock is used for adaptive equalization, then the equalizer can effectively track time-varying signals and correct spectral aberration, but it becomes difficult to maintain the clock synchronization due to inter-code crosstalk, chromatic dispersion and polarization mode dispersion
Solution Approach 1:
The patent extracts and removes the clock recovery circuit from the system, transitioning from synchronous to asynchronous operation. The monitoring device detects down-sampling phase and controls coefficient updates without requiring external clock synchronization, thereby eliminating the maintenance burden of clock sync while preserving equalization effectiveness.
Solution Approach 2:
The system performs self-synchronization by using the monitoring device to detect phase information from the signal itself. The coefficient updating unit automatically adjusts equalizer coefficients based on detected phase without external clock control, enabling the system to self-adapt to timing variations caused by dispersion effects.
2Adaptability or versatility
If coefficient updates are continuously performed in the adaptive equalizer, then the equalizer can track time-varying signals in real time, but system complexity increases due to the need for clock recovery circuits and precise timing control
Solution Approach 1:
The patent implements dynamic coefficient updating controlled by the monitoring device. Instead of continuous updates requiring precise clock synchronization, the system dynamically updates coefficients only when phase conditions are met, as determined by the monitoring device's phase detection and comparison with predetermined ranges.
Solution Approach 2:
The system employs periodic phase detection and conditional coefficient updates rather than continuous operation. The monitoring device periodically checks the down-sampling phase and triggers coefficient updates only when appropriate, reducing system complexity while maintaining tracking capability.
3Device complexity
If the adaptive equalizer operates under asynchronous clock conditions, then clock recovery circuits are eliminated and system complexity is reduced, but it becomes challenging to select appropriate sampling points for coefficient updates
Solution Approach 1:
The monitoring device serves as an intermediary between the asynchronous signal and the coefficient updating unit. It detects down-sampling phase, compares it with predetermined ranges, and controls the switching unit to enable coefficient updates only when phase conditions are satisfied, thereby solving the sampling point selection problem in asynchronous operation.
Solution Approach 2:
The patent replaces the mechanical/clock-based timing control system with a phase-detection-based control system. Instead of relying on external clock signals and timing circuits, the system uses the monitoring device to detect phase information and control coefficient updates, eliminating complex timing mechanisms.
Data Source
AI summary
An adaptive equalizer and an adaptive equalizing method are provided. The adaptive equalizer includes an adaptive equalizing unit, for adaptively equalizing an inputted signal to output the equalized signal; a coefficient updating unit, for updating a coefficient of a filter of the adaptive equalizing unit; a switching unit, connected between the coefficient updating unit and the adaptive equalizing unit and a monitoring device, for controlling on or off of the switching unit in accordance with the fact that a down sampling phase of the inputted signal or a down sampling phase of the equalized signal is within a predetermined range. When the switching unit is on, the coefficient updating unit is capable of updating the coefficient of the adaptive equalizing unit, and when the switching unit is off, the coefficient updating unit is incapable of updating the coefficient of the adaptive equalizing unit.