DAC and ADC Harmonic Distortion Separation for Precise Calibration
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Solution Overview
Problem
Existing methods for compensating harmonic distortions in digital to analog and analog to digital conversion systems fail to accurately separate and correct distortions introduced by the DAC and ADC sides, leading to incorrect measurement results due to frequency-dependent amplitude gain and phase shifts in the analog path, and mismatched frequency transfer characteristics between the calibration and device-under-test.
Innovation Solution
The solution involves determining and compensating the respective contributions of the DAC and ADC sides by measuring amplitude gain and phase shift of calibration paths, using Fast Fourier Transformation to analyze distortions, and solving equations to calculate distortion contributions, allowing for precise compensation of harmonic distortions on both sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If joint distortions are compensated on the DAC side using prior-art methods, then the measurement process is simplified, but the measurement precision deteriorates due to frequency-dependent amplitude gain and phase shifts in the analog path
Solution Approach 1:
The patent divides the measurement system into two separate measurement chains: one for measuring DAC side distortions and another for measuring ADC side distortions. Each chain independently measures and compensates its respective distortions, avoiding the need to compensate joint distortions while accounting for frequency-dependent characteristics of the analog path.
Solution Approach 2:
The patent introduces an intermediary measurement approach where the analog path's frequency-dependent characteristics are separately characterized and used to decouple the distortion measurements. This intermediary measurement of the analog path properties enables accurate separation of DAC and ADC distortion contributions.
2Reliability
If joint distortions are compensated using calibration functions, then compensation is achieved, but the device complexity increases due to mismatched frequency transfer characteristics between calibration and device-under-test
Solution Approach 1:
The patent eliminates the need for complex calibration functions by segmenting the measurement into independent DAC and ADC sides. Each side is measured and compensated separately without requiring calibration of joint distortions, thereby reducing device complexity while maintaining compensation effectiveness.
Solution Approach 2:
The patent extracts and removes the problematic joint distortion compensation requirement by independently measuring and compensating DAC and ADC distortions separately. This extraction of the joint measurement requirement simplifies the system while maintaining accurate distortion compensation.
3Ease of operation
If harmonic distortions are measured in the digital signal behind the ADC, then the measurement is straightforward, but the measured values represent a combination of DAC, analog path, and ADC distortions making it difficult to identify individual contributions
Solution Approach 1:
The patent segments the distortion measurement into two independent measurement chains, allowing each chain to measure only its respective side's distortions. This segmentation preserves individual distortion contribution information while maintaining measurement straightforwardness through independent processing.
Solution Approach 2:
The patent implements feedback mechanisms where each measurement chain uses its measured distortion values to independently compensate its respective side. This feedback approach maintains simple digital signal measurement while recovering individual distortion contribution information through separate compensation loops.
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
This approach generates a distortion-free analog sine signal from the DAC side and prevents false distortions from the ADC side during measurement, achieving accurate harmonic distortion compensation and improving measurement precision.
Implementation Method 1
using Fast Fourier Transformation to analyze distortions
Data Source
AI summary
A method and an apparatus for determining and compensating respective harmonic distortions of digital to analog and analog to digital conversions are described. A signal from a digital to analog converter is passed through a plurality of calibration paths. Output signals from each calibration path, converted by an analog to digital converter, are analyzed in order to determine the harmonic distortions introduced by each side of the chain separately. One embodiment represents a digital sine generator which has harmonic distortions of its analog output continually compensated. Another embodiment compensates harmonic distortions introduced by an analog to digital converter in order to measure harmonic distortions of an analog signal precisely. Other embodiments are described and shown.