Vernier TDC Line Calibration for Quantization Error Reduction
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Solution Overview
Problem
Conductors in radio frequency circuits, such as metal traces, introduce reactance that causes signal propagation delays, leading to inaccurate signal comparison and quantization errors in Time-to-Digital Converter (TDC) devices, particularly in high-frequency applications like radar, where precise phase noise measurements are required.
Innovation Solution
The implementation of a TDC with Vernier architecture and tunable capacitances allows for calibration of conductive lines to ensure equal capacitance across parallel interconnect lines, using buffers and arbiters to isolate and modify capacitances, ensuring precise signal propagation and minimizing quantization errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional TDC devices are used without calibration, then the device structure is simple, but signal propagation delays cause quantization errors and reduced measurement precision
Solution Approach 1:
The patent applies preliminary action by performing calibration of the TDC device before actual time measurements. A calibration module pre-adjusts tuning capacitances to compensate for conductor reactance effects, ensuring that measurement paths are properly balanced before signal comparison occurs. This preliminary calibration eliminates quantization errors that would otherwise degrade measurement precision.
Solution Approach 2:
The patent introduces tuning capacitances as intermediary elements between the signal paths and the TDC core. These capacitances act as mediators that can be adjusted to compensate for unequal propagation delays in conductors. The calibration module modifies these intermediary capacitances to balance the measurement paths, thereby improving time measurement precision without fundamentally changing the TDC architecture.
2Measurement precision
If tuning capacitances are added for calibration, then measurement precision improves, but device complexity and manufacturing difficulty increase
Solution Approach 1:
The patent applies parameter changes by introducing variable capacitance values that can be tuned during calibration. The tuning capacitances allow adjustment of electrical parameters (capacitance) to compensate for manufacturing variations in conductor reactance. This enables post-fabrication calibration to achieve precise phase noise measurements without requiring extremely tight manufacturing tolerances.
Solution Approach 2:
The patent introduces dynamic adjustability through the calibration module that can modify tuning capacitance values. Rather than fixed capacitances, the system allows dynamic reconfiguration during calibration to optimize performance. This dynamic approach enables the device to adapt to actual propagation delays, improving measurement accuracy while maintaining reasonable manufacturing complexity.
3Manufacturing precision
If calibration is performed to eliminate quantization errors, then time resolution improves, but calibration time and process complexity increase
Solution Approach 1:
The patent applies self-service by implementing an automated calibration module that performs the calibration process without extensive manual intervention. The calibration module automatically adjusts tuning capacitances based on detected signal characteristics, reducing the time and expertise required for calibration. This self-calibrating capability achieves fine time resolution while minimizing the time loss associated with the calibration process.
Solution Approach 2:
The patent uses feedback mechanisms where the TDC device monitors its own performance and feeds this information back to the calibration module. The calibration module uses this feedback to iteratively adjust tuning capacitances until optimal time resolution is achieved. This closed-loop feedback approach streamlines the calibration process, reducing both time and complexity compared to open-loop calibration methods.
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 enables precise calibration of TDC devices, achieving fine time resolution and accurate phase noise measurements, suitable for GHz range applications, by ensuring consistent signal propagation across parallel lines, thereby enhancing the performance of digital Phase Locked Loops (PLLs) in radio frequency circuits.
Implementation Method 1
a first set of tuning capacitances configured to be selectively connected to a one of a signal line or a reference frequency line traversing the second module to modify a capacitance of the one of the signal line or the reference frequency line
Data Source
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AI summary
A Time to Digital converter (TDC) may have a Vernier architecture of multiple successive modules arranged in series. Each of the modules may output an indication of a differential in phase between two received signals. Each module may include two signal lines for the received signals, and it may be desirable to calibrate the two signal lines. To this end, a signal output from a proceeding module may be provided to both signal lines of a succeeding module and used as a reference or calibration signal to calibrate the two signal lines of the module.