Photonic ADC Linearization via Multidimensional Lookup Table
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Solution Overview
Problem
Nonlinear distortions in photonic analog to digital converter (pADC) systems limit the effective number of bits (ENOB) and spurious free dynamic range (SFDR) of electronic intelligence (ELINT) receiver systems, affecting the accuracy of signal recovery.
Innovation Solution
A method and system for linearizing pADC systems by generating a series of optical pulse trains with discrete power levels, phase modulating them with calibration voltages, and creating a multidimensional lookup table to correct nonlinear behaviors, using phase and optical power level mappings to enhance signal constellations and recover accurate digital outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multi-dimensional quantization (MDQ) or multi-phase quantization (MPQ) is used to enhance dynamic range, then effective number of bits (ENOB) and spurious free dynamic range (SFDR) are improved, but nonlinear distortions worsen and limit the ENOB and SFDR of the receiver system
Solution Approach 1:
The patent applies preliminary action by performing linearization calibration before actual signal conversion. A calibration signal is fed through the pADC system to measure nonlinear distortions, and correction data is stored in lookup tables. During operation, these pre-computed correction values are applied to compensate for nonlinear effects, allowing the system to achieve high ENOB and SFDR without being limited by the inherent nonlinear distortions of the MDQ/MPQ architecture.
Solution Approach 2:
The patent implements feedback by measuring the actual output of the pADC system during calibration and using this information to generate correction factors. The system feeds the calibration signal through the complete conversion chain, measures the distorted output, and uses this feedback to compute and store correction data that compensates for the nonlinearities. This closed-loop approach enables the system to overcome the harmful nonlinear distortions while maintaining the benefits of multi-dimensional quantization.
2Measurement precision
If multi-dimensional quantization (MDQ) or multi-phase quantization (MPQ) is used to enhance dynamic range, then spurious free dynamic range (SFDR) is improved, but nonlinear distortions worsen and limit the SFDR of the receiver system
Solution Approach 1:
The patent applies preliminary action by performing linearization calibration before actual signal conversion. A calibration signal is fed through the pADC system to measure nonlinear distortions, and correction data is stored in lookup tables. During operation, these pre-computed correction values are applied to compensate for nonlinear effects, allowing the system to achieve high ENOB and SFDR without being limited by the inherent nonlinear distortions of the MDQ/MPQ architecture.
Solution Approach 2:
The patent implements feedback by measuring the actual output of the pADC system during calibration and using this information to generate correction factors. The system feeds the calibration signal through the complete conversion chain, measures the distorted output, and uses this feedback to compute and store correction data that compensates for the nonlinearities. This closed-loop approach enables the system to overcome the harmful nonlinear distortions while maintaining the benefits of multi-dimensional quantization.
3Measurement precision
If calibration and correction of nonlinear behaviors is performed to improve accuracy, then linearity and noise performance are enhanced, but system complexity increases due to multidimensional lookup table generation and processing
Solution Approach 1:
The patent applies segmentation by dividing the calibration process into distinct stages: generating calibration signals with specific voltage ramps, measuring the system response, organizing the measurement data into multidimensional lookup tables, and applying corrections during operation. The lookup tables themselves are segmented into multiple dimensions corresponding to different signal parameters, allowing complex nonlinear corrections to be broken down into manageable discrete values that can be efficiently stored and accessed.
Solution Approach 2:
The patent uses dimensionality change by creating multidimensional lookup tables that organize calibration data across multiple dimensions corresponding to different signal parameters. This multidimensional structure allows the system to handle complex nonlinear distortions by distributing correction data across multiple dimensions rather than requiring a single complex correction function, reducing the processing burden while maintaining accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution significantly enhances the linearity and noise performance of ELINT receivers by correcting nonlinear distortions, achieving near-ideal performance in terms of ENOB and SFDR, as demonstrated by restored signal quality and suppressed noise peaks.
Implementation Method 1
imparting the voltage information of the input signal onto each optical pulse train via a phase modulator
Data Source
AI summary
A method and related system for linearizing a photonic ADC sampling system of an ELINT receiver includes modulating optical pulse trains of varied pulse amplitudes based on a generated ramped-voltage calibration signal. The modulated pulse trains are demodulated into I/Q components to generate signal constellations. Equivoltage radials are defined by points of the signal constellations sharing a common calibration voltage and a common phase angle of the modulator. A lookup table is generated by mapping the signal constellations and equivoltage radials to a coordinate system to determine, for each coordinate bin, a corresponding pulse amplitude and phase angle. The generated lookup table may be used to correct nonlinear distortions in recovered output signals, preserving high-ENOB performance and increasing the dynamic range of the receiver.