Time-Interleaved DAC Equalization for Sub-DAC Frequency Misalignment
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Solution Overview
Problem
Time-interleaved digital to analog converters (DACs) suffer from spurious frequency components due to misalignments in the frequency responses of their sub-DACs, which are difficult to calibrate effectively using existing methods, especially in production or operational environments where sophisticated measurement tools are not readily available.
Innovation Solution
A method and system for calibrating time-interleaved DACs by equalizing frequency response misalignments using a simple spectrum analyzer, involving the determination of spurious frequency components' amplitudes and phases, and calculating equalizing frequency responses to correct sub-DAC gains, allowing for the suppression of spurious components without direct measurement of sub-DAC frequency responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If calibration is performed over full output bandwidth using sophisticated measurement tools, then frequency response misalignment can be corrected, but device complexity and measurement cost increase
Solution Approach 1:
The patent replaces expensive, sophisticated measurement tools with a simple spectrum analyzer that is widely available and inexpensive. This allows calibration to be performed in production environments without requiring specialized equipment, directly resolving the contradiction between measurement precision and device complexity.
Solution Approach 2:
The calibration method enables the DAC to self-diagnose and self-correct its frequency response misalignments by measuring spurious components and automatically calculating equalizing coefficients. This eliminates the need for complex external measurement systems and expert intervention, allowing calibration to be performed using only simple spectrum analyzer data.
2Measurement precision
If direct measurement of sub-DAC frequency responses is performed, then misalignment can be identified, but measurement complexity and time increase
Solution Approach 1:
Instead of directly measuring sub-DAC frequency responses, the method measures the harmful spurious frequency components produced by misalignments and uses this information to infer and correct the underlying problems. This converts the measurement of unwanted artifacts into a beneficial calibration process, avoiding direct complex measurements while still achieving correction.
Solution Approach 2:
The patent performs preliminary measurement of spurious components and calculates equalizing coefficients before actual operation. By preparing the correction data in advance using simple measurements, the system can quickly apply corrections without requiring time-consuming direct frequency response measurements during operation.
3Object-generated harmful factors
If multiple calibration parameters are adjusted, then spurious components can be reduced, but calibration complexity increases
Solution Approach 1:
The patent applies local quality correction by calculating specific equalizing coefficients for each sub-DAC based on the measured spurious components. Rather than requiring comprehensive adjustment of all possible calibration parameters, the method focuses on applying targeted local corrections to each sub-DAC's frequency response, simplifying the overall calibration process while effectively reducing spurious components.
Data Source
AI summary
A method and system for calibrating a time-interleaved digital to analog converter (DAC) provides equalization of frequency response misalignments in sub-DACs forming the DAC. In a calibration mode, test signals are applied to an DAC and output amplitudes and phases of are measured. From the measured values, complex values of the gains of the respective sub-DACs. hm(F) are determined and a specified target frequency response T(F) for a tandem connection equalizer-DAC is determined. For each of a plurality of test frequencies, complex values of equalizer gains Eqm are determined from Eqm(F)=T(F)/hm(F), to form equalizing frequency responses. Sets of equalizing coefficients Cm(p) pursuant to discrete Fourier transforms on Eqm(F). In an operation mode, a digital input signal is transformed input into an equalized digital signal E(n) through use of the sets of equalizing coefficients Cm(p).