Joint Transmitter Receiver Gain Optimization for High-Speed Serial Data
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Solution Overview
Problem
High-speed data transmission beyond 8 Gbps is hindered by signal impairments like intersymbol interference and noise, requiring complex analog front-end equalization that is costly to implement and may not fully correct frequency-dependent distortions, leading to unacceptably poor performance and lengthy initialization delays due to fixed TXFIR coefficients and temperature-induced receiver gain variations.
Innovation Solution
Joint adaptation of transmitter and receiver coefficients during initialization, with a transmitter mapper translating receiver gain updates into transmitter amplitude updates via a back channel, masking gain updates within a constrained range to reserve VGA range for PVT variations and improve linear equalization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If complex analog front-end equalization is used to correct frequency-dependent distortions, then receiver performance is improved, but device complexity and implementation cost increase
Solution Approach 1:
The patent combines transmitter and receiver equalization functions into a joint adaptation system. The transmitter FIR filter and receiver VGA/analog equalizer work together with coordinated coefficient adaptation, merging previously separate equalization efforts into a unified system that achieves better performance without proportionally increasing complexity.
Solution Approach 2:
The patent implements dynamic coefficient adaptation where transmitter and receiver equalization coefficients are continuously adjusted during initialization based on feedback. The system transitions from static fixed coefficients to dynamic adaptive coefficients that optimize performance for different channel conditions and temperature variations.
2Device complexity
If fixed TXFIR coefficients are used for initialization, then device complexity is reduced, but adaptability to different channel conditions and temperature variations deteriorates
Solution Approach 1:
The patent implements a feedback mechanism during initialization where the receiver measures signal quality metrics and communicates back to the transmitter, which then adjusts its FIR coefficients accordingly. This closed-loop feedback enables adaptive coefficient selection without requiring extremely complex open-loop prediction algorithms.
Solution Approach 2:
The patent changes the approach from selecting from fixed preset coefficients to dynamically adjusting coefficient values based on measured channel conditions. The system adapts FIR filter coefficients and VGA gain values in response to temperature changes and channel variations, transforming static parameters into dynamic adjustable ones.
3Reliability
If full VGA gain range is used during initialization, then receiver signal quality is improved, but range for compensating PVT variations is reduced
Solution Approach 1:
The patent performs preliminary equalization using the FIR filter during initialization to establish good signal quality before normal operation. By pre-distorting the signal with the FIR filter, the system reduces the burden on the VGA during normal operation, allowing the VGA to maintain headroom for compensating temperature and process variations.
Solution Approach 2:
The patent applies partial equalization action by dividing the equalization function between the transmitter FIR filter and receiver VGA. Rather than relying solely on the VGA for all equalization needs, the system uses the FIR filter to handle frequency-dependent distortions, allowing the VGA to operate within a constrained but sufficient range that maintains both signal quality and adaptability.
4Measurement precision
If lengthy initialization processes are used for coefficient adaptation, then measurement precision of channel conditions is improved, but productivity and data transmission start time deteriorate
Solution Approach 1:
The patent implements continuous coefficient adaptation during the entire initialization period rather than using discrete stepped adjustments. The system continuously refines FIR and VGA coefficients based on ongoing measurements, maintaining useful adaptation action throughout the initialization process to achieve both precision and reasonable speed.
Solution Approach 2:
The patent uses periodic measurement and update cycles during initialization where the system periodically assesses signal quality metrics and adjusts coefficients in controlled intervals. This periodic approach balances thorough channel characterization with reasonable initialization timing, avoiding both excessively long continuous measurement and insufficient sampling.
Data Source
AI summary
Embodiments of the present invention allow for adjustment of transmitter amplitude during joint transmitter (TX) and receiver (RX) equalization. During joint TX and RX adaptation, when the receiver requires a gain update, the receiver gain update is masked above or below a preset range. The RX gain update (instruction) is encoded into a transmitter amplitude update (instruction) transferred through back channel communication. The translation of RX gain to TX amplitude update is performed after the RX gain reaches a specified range. Such masking, encoding and translation reserves a certain amount RX gain range to account for RX gain variation due to process, voltage, and temperature (PVT) changes over time, and also to offer better linear equalization in the receiver over a constrained VGA bandwidth.