DAC DC Offset Calibration Using an Incremental ADC
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Solution Overview
Problem
Existing digital-to-analog converters (DACs) in wireless communication devices suffer from direct current (DC) offset issues that affect performance specifications like carrier suppression and local oscillator leakage, and current methods for offset calibration are inadequate or costly.
Innovation Solution
Implementing an incremental analog-to-digital converter (IADC) with a switch circuit to measure and adjust for DC offset in DACs by performing flip and non-flip mode measurements, reducing the impact on DAC operation and measurement time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional offset calibration methods are used for DAC, then DC offset can be measured, but the measurement process is time-consuming and costly
Solution Approach 1:
The patent extracts only the essential function needed for DC offset measurement by using an existing IADC (incremental ADC) already present in the system, rather than employing traditional complex calibration equipment. The IADC's differential input is configured to measure the DAC output directly, eliminating the need for separate calibration instruments and reducing measurement time while maintaining accuracy.
Solution Approach 2:
The system uses its own internal resources (the IADC that is already part of the wireless communication device) to perform the DC offset calibration of the DAC. This self-service approach eliminates the need for external calibration equipment and reduces both time and cost, as the IADC is already integrated into the device's normal operation.
2Reliability
If comprehensive offset calibration is performed, then DAC performance specifications are met, but device complexity increases
Solution Approach 1:
The IADC serves multiple functions: it performs normal analog-to-digital conversion for communication operations and simultaneously performs DC offset calibration of the DAC. By making the IADC multi-functional, the patent avoids adding separate calibration equipment, thereby reducing device complexity while ensuring DAC performance specifications are met through accurate offset measurement.
3Measurement precision
If existing calibration methods are used, then DC offset can be corrected, but carrier suppression and local oscillator leakage specifications are not met
Solution Approach 1:
The patent implements a feedback mechanism where the IADC continuously monitors the DAC output and measures the DC offset, which is then used to adjust and correct the DAC performance. This closed-loop feedback ensures that not only is the DC offset corrected accurately, but also that carrier suppression and local oscillator leakage specifications are met, as the calibration directly targets the parameters affecting these performance metrics.
Data Source
AI summary
Certain aspects of the present disclosure provide techniques and apparatus for digital-to-analog conversion. An example apparatus generally includes a digital-to-analog converter (DAC), an incremental analog-to-digital converter (IADC) having a first input coupled to a first output of the DAC, and a controller coupled to the DAC and the IADC. The controller is configured to determine a direct current (DC) offset associated with the DAC using the IADC and control a mission-mode digital input signal of the DAC based on the DC offset.