Continuous-Time Sigma-Delta Modulator Quantizer Offset Calibration
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Solution Overview
Problem
Continuous-time low-pass sigma-delta modulators face performance degradation due to non-zero offsets in the quantizer, which increase the noise floor and deteriorate the signal-to-noise ratio (SNR).
Innovation Solution
An offset calibration method is introduced, which includes a data monitoring module and an offset calibration module added to the continuous-time sigma-delta modulator. This method pre-calibrates the quantizer offset based on the signal-to-noise ratio and a preset calibration algorithm, generating an offset calibration digital code that is used to calibrate the quantizer offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offset calibration is not performed, then the device complexity remains low, but the signal-to-noise ratio deteriorates due to non-zero quantizer offsets
Solution Approach 1:
The patent applies preliminary action by performing offset calibration before normal operation. The calibration module pre-calibrates the quantizer offset using a calibration signal, stores the calibration code, and then uses this pre-determined code during normal operation to compensate for offset effects, thereby improving signal-to-noise ratio without adding complex real-time calibration mechanisms
Solution Approach 2:
The patent introduces an intermediary calibration module that acts as a mediator between the quantizer and the output. This module captures the offset effect through calibration, stores it in a register, and then subtracts it from the quantizer output during normal operation, effectively eliminating offset impact on signal-to-noise ratio while keeping the overall system structure relatively simple
2Measurement precision
If offset calibration modules are added, then the signal-to-noise ratio improves, but the device complexity increases
Solution Approach 1:
The patent extracts the offset calibration function as a separate, independent module from the main signal processing path. The calibration module operates independently during calibration phase, captures offset information, and then this extracted calibration data is used to compensate the main signal path, thereby improving signal-to-noise ratio while minimizing interference with the core modulator structure
Solution Approach 2:
The patent discards the calibration signal after extracting the offset information, and recovers the original signal by subtracting the calibrated offset from the quantizer output. The calibration signal is used only temporarily to determine the offset code, which is then discarded and replaced by the recovered original signal during normal operation, maintaining clean signal paths
Data Source
AI summary
A continuous-time sigma-delta modulator includes a continuous-time sigma-delta modulation module, a data monitoring module, and an offset calibration module. The data monitoring module and the offset calibration module are added on the basis of the continuous-time sigma-delta modulation module. Based on a hardware architecture design of the offset calibration module and the data monitoring module, with reference to software data processing, an offset of a quantizer in the continuous-time sigma-delta modulation module can be pre-calibrated based on feedback of a signal-to-noise ratio of a digital signal and a preset calibration algorithm, to obtain an offset calibration digital code. Finally, the offset calibration digital code is input into the quantizer by using the offset calibration module, and the offset of the quantizer is finally calibrated based on the offset calibration digital code.