Adaptive ADC Threshold Correction in Digital Coherent Receivers
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Solution Overview
Problem
Conventional digital coherent receivers face challenges in achieving high-resolution and high-speed analog-to-digital conversion due to fluctuations in AD converter elements, circuit speed limitations, and power consumption, which affects waveform distortion compensation, especially at low optical signal-to-noise ratios and with multi-level modulation.
Innovation Solution
A digital receiver that adjusts discrimination levels of the AD converter based on signal quality monitoring, using a discrimination level control signal to set optimal discrimination levels and correct transfer functions, thereby improving effective resolution and compensating for waveform distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ultra-high-speed AD converters are used to increase sampling rate, then productivity is improved, but measurement precision deteriorates due to characteristics fluctuations among elements
Solution Approach 1:
The patent changes the discrimination levels parameter of the AD converter from fixed to dynamically adjustable. By adapting the discrimination levels to the actual signal distribution characteristics, the system maintains high effective resolution even at ultra-high sampling rates where element fluctuations occur. This parameter adaptation allows the converter to optimize its transfer characteristics for different operating conditions.
Solution Approach 2:
The patent implements feedback by monitoring the signal distribution characteristics and using this information to adjust the discrimination levels of the AD converter. The system continuously adapts the converter parameters based on the actual input signal statistics, ensuring optimal effective resolution is maintained despite speed-related element fluctuations.
2Measurement precision
If discrimination levels are adjusted to match signal density, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent enables the AD converter to self-adjust its discrimination levels based on the signal distribution characteristics it receives. The system uses the signal's own statistical properties to determine the optimal discrimination levels, eliminating the need for external complex calibration equipment or manual adjustment mechanisms.
Solution Approach 2:
The patent performs preliminary characterization of the signal distribution before the main conversion process. By analyzing the signal statistics in advance and pre-setting the discrimination levels accordingly, the system avoids the need for complex real-time adjustment mechanisms during operation.
3Productivity
If high-speed AD conversion is implemented, then productivity is improved, but manufacturing precision worsens due to difficulty in maintaining equally spaced discrimination levels
Solution Approach 1:
The patent transitions from static, equally-spaced discrimination levels to dynamic, adaptively-positioned discrimination levels. The system adjusts the discrimination level positions based on the actual signal distribution, allowing unequal spacing that matches the signal characteristics. This dynamic approach compensates for the inability to maintain precise equal spacing at high conversion speeds.
Data Source
AI summary
A digital receiver includes: an analog-to-digital (AD) converter (102) for setting discrimination levels in accordance with a discrimination level control signal and converting an analog input signal into a digital signal based on the set discrimination levels; a discrimination level adjusting circuit (104) for generating the discrimination level control signal and outputting the discrimination level control signal to the AD converter; a signal quality monitoring portion (108) for generating a transfer function correction control signal, which is information about a transfer function of the AD converter; and a transfer function correcting circuit (106) for performing signal processing on the digital signal so as to cancel a gap between the transfer function of the AD converter and an initial transfer function based on the transfer function correction control signal.