Time-to-Digital Converter Range Extension With Fine Phase Resolution
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Solution Overview
Problem
Time to Digital Converters (TDCs) face challenges in achieving a wide input range with high resolution and precision, particularly in low power, high performance RF systems, where existing solutions struggle to accurately measure time differences with sufficient range and resolution.
Innovation Solution
The implementation of a TDC system that combines coarse and fine measurements using a ring oscillator for coarse estimation and a two-dimensional Vernier structure for fine resolution, allowing for a wide input range of 2.5 ns to 5 ns with a resolution of 5 ps, by integrating these components within a low power RF receiver circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a simple counter-based TDC is used, then the device complexity is low, but the measurement precision and resolution are insufficient
Solution Approach 1:
The TDC is divided into multiple independent measurement channels (e.g., 8 channels) that can be selectively activated. Each channel contains its own delay line and counter, allowing the system to achieve high resolution by combining multiple coarse measurements rather than requiring a single complex high-resolution counter.
Solution Approach 2:
The patent implements a hierarchical measurement structure where fine-grained delay elements (e.g., 50ps resolution) are nested within coarser measurement channels. The delay lines are segmented into multiple stages, with each stage providing finer resolution than the previous, creating a nested structure that achieves high overall resolution through combination of multiple measurement levels.
2Adaptability or versatility
If the TDC input range is extended to cover wider time differences, then the adaptability improves, but the measurement precision deteriorates
Solution Approach 1:
The TDC implements dynamic range adjustment by allowing selective activation of different measurement channels based on the expected time difference magnitude. The system can switch between different delay line configurations and counter resolutions adaptively, enabling it to maintain high precision across a wide input range by selecting the appropriate measurement scale for each measurement task.
Solution Approach 2:
The patent changes the measurement parameters (delay line length, counter resolution, sampling rate) dynamically based on the input signal characteristics. By adjusting these parameters, the TDC can optimize its resolution for the current measurement range, preventing precision degradation when operating across wide time differences.
3Measurement precision
If multiple measurement channels are added to increase range and resolution, then the measurement precision improves, but the use of energy increases
Solution Approach 1:
The patent implements partial action by allowing the TDC to activate only the necessary number of measurement channels based on the current measurement requirements. Instead of keeping all channels continuously active, the system dynamically enables only those channels needed to achieve the desired resolution for the current input range, significantly reducing power consumption while maintaining measurement precision.
Solution Approach 2:
The TDC channels are designed to be universal and interchangeable, with identical functionality and characteristics. This multi-functionality allows the system to achieve high resolution by combining results from multiple identical, low-power channels rather than requiring a single complex high-power channel, thereby reducing overall power consumption while maintaining precision.
4Measurement precision
If the counter update rate is increased to improve time measurement resolution, then the measurement precision improves, but the loss of time increases due to counter rollover handling
Solution Approach 1:
The patent implements preliminary action by pre-configuring multiple counters with different overflow characteristics and pre-establishing the combination logic for merging their measurements. The system prepares the measurement architecture in advance with multiple parallel counters that can be quickly combined, eliminating the need for time-consuming rollover detection and correction during actual measurements, thus reducing time loss while maintaining high resolution.
Data Source
AI summary
Systems and methods are described for determining a phase measurement difference between a received modulated signal and a local clock signal. An adjusted local clock phase measurement may be determined by subtracting, from the phase measurement difference, a phase correction that is based on the frequency difference between the modulator signal's carrier frequency and the local clock's frequency. A phase modulation value may be generated by scaling the adjusted local clock phase measurement. The scaling may be based on a ratio of the modulated signal's carrier frequency and the local clock's frequency. The phase correction may be based on (i) a count of periods of the modulated signal occurring between each corrected phase measurement and (ii) a difference between the carrier frequency and the local clock frequency.