DAC Signal Calibration Using Codeword Offset Mapping
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Solution Overview
Problem
Current DAC circuits suffer from manufacturing process offsets that result in non-ideal amplitude and shape of output analog signals, significantly affecting system performance.
Innovation Solution
A digital-to-analog conversion apparatus and method incorporating a DAC circuit with current sources that can switch between two states, an echo transmission circuit, a calibration circuit, and a calibration parameter calculating circuit to categorize and cancel current offsets, updating a codeword offset mapping table to calibrate the signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a current-output type DAC circuit is used to achieve fast conversion speed, then conversion speed is improved, but manufacturing process offsets cause non-ideal amplitude and shape of output signal affecting system performance
Solution Approach 1:
The patent performs calibration in advance to determine offset amounts for different codewords and stores them in a calibration result storage unit. During normal operation, the pre-calculated offset compensation values are directly applied to correct manufacturing offsets without requiring real-time calculation, thus maintaining fast conversion speed while improving output signal accuracy.
Solution Approach 2:
The system uses its own output analog signal to generate echo signals and performs self-calibration by measuring the actual offsets produced by its current sources. The calibration process leverages the system's inherent echo transmission capability to automatically characterize and correct its own manufacturing offsets without external intervention.
2Measurement precision
If extensive calculations are performed to calibrate each codeword offset individually, then calibration accuracy is improved, but calculation complexity and time consumption increase
Solution Approach 1:
The patent segments the calibration process into two distinct phases: an offline calibration phase where offset amounts are measured and stored in a lookup table, and an online operation phase where pre-calculated compensation values are directly applied. This segmentation separates the complex measurement calculations from the simple compensation operations, achieving high calibration accuracy without requiring complex real-time calculations.
Solution Approach 2:
Instead of performing complex calculations for each codeword during operation, the system creates a copy of the calibration results in the form of a lookup table storing offset amounts for different codewords. During normal operation, the system simply retrieves and applies the pre-stored compensation values, replacing complex calculations with simple table lookups and additions.
Data Source
AI summary
The present invention discloses a DAC method having signal calibration mechanism is provided. Operation states of current sources are controlled to generate an output analog signal by a DAC circuit according to a codeword of an input digital signal. An echo signal is generated by an echo transmission circuit according to the output analog signal. The codeword is mapped to generate an offset signal by a calibration circuit according to a codeword offset mapping table. The offset signal is processed to generate an echo-canceling signal by an echo-canceling circuit. By a calibration parameter calculation circuit, offset amounts are generated according to a difference between the echo signal and the echo-canceling signal, the offset amounts are grouped to perform statistic operation according to the operation states and current offset values are calculated according to calculation among groups and converted to codeword offset values to update the codeword offset mapping table.