Receiver Distortion Compensation Circuit for Nonlinear Analog Front Ends
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Solution Overview
Problem
Analog front ends in communication receivers introduce nonlinear distortion, degrading the performance of decision-feedback equalization systems, especially at high data rates due to inherent limitations in analog circuitry.
Innovation Solution
A distortion compensation circuit is implemented in the receiver's analog front end, which adjusts the input signal amplitude and applies a weighting factor to cancel out nonlinear distortion terms, primarily focusing on the third-order term, thereby reducing overall distortion in the output signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If analog front end circuitry is used to amplify and process signals, then signal processing capability is improved, but nonlinear distortion is introduced that degrades receiver performance
Solution Approach 1:
The patent measures the actual nonlinear distortion generated by the analog front end circuits and uses this measured distortion characteristic to synthesize a compensation signal. The compensation signal is designed to have equal magnitude but opposite phase to the measured distortion, thereby converting the harmful distortion effect into a beneficial cancellation mechanism that improves overall receiver performance
Solution Approach 2:
The patent introduces a distortion compensation circuit as an intermediary component between the analog front end and the decision feedback equalizer. This intermediary circuit measures the distortion produced by the analog circuits and generates a compensating signal that is subtracted from the main signal path, effectively mediating the harmful interaction between analog amplification and nonlinear distortion
2Productivity
If data rate is increased to improve communication speed, then productivity is improved, but distortion compensation becomes more critical and performance degrades without it
Solution Approach 1:
The patent performs distortion measurement and compensation signal generation in advance before the actual data reception and detection process. By pre-characterizing the nonlinear distortion of the analog front end and preparing the compensation signal beforehand, the system ensures that distortion compensation is already in place when high-rate data transmission occurs, maintaining reliability at increased data rates
Data Source
AI summary
A receiver containing analog circuitry that generates distortion, a distortion compensation circuit coupled to an output of the analog circuitry, and a slicer, operating as a signal peak detector, coupled to the distortion compensation circuitry. The distortion compensation circuit has a subtractor, a function generator, and a weighting circuit. The subtractor has a first input coupled to the output of the analog circuitry, a second input, and an output. The function generator has an input coupled to the first input of the subtractor. The weighting circuit, responsive to a weighting coefficient, is coupled between an output of the function circuit and the second input of the first subtractor. The function generator has a transfer function with a third-power term and the weighting coefficient is set to a value based on the level of the signal peaks that will least partially reduce distortion in signals on the output of the subtractor.