Ramp-Scanned ADC With Histogram Correction for LIDAR Jitter
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Solution Overview
Problem
Current analog-to-digital converters for high-speed LIDAR measurements are expensive and consume high power, while existing time-to-digital converters offer high time resolution but are not cost-efficient for scanning analog signals from photodiodes or laser diodes at high scanning rates.
Innovation Solution
An analog-to-digital converter comprising a time-to-digital converter and a histogram block that scans analog signals using a ramp signal, generating a time-correlated histogram to correct for time jitter and combine values, thereby reducing the effects of time jittering and improving scanning efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional analog-to-digital converters are used for high-speed LIDAR measurements, then measurement speed is improved, but cost and power consumption increase significantly
Solution Approach 1:
The patent segments the analog signal scanning task into multiple time intervals, using a ramp signal to divide the measurement period into discrete segments. Each segment is processed independently by the time-to-digital converter, allowing for lower sampling rates while maintaining overall measurement speed through histogram accumulation across multiple segments.
Solution Approach 2:
The patent employs periodic ramp signals to scan the analog input signal at reduced rates, accumulating measurements over multiple periods in a histogram. This periodic approach allows the system to achieve high effective scanning rates through statistical accumulation rather than requiring continuously high-speed conversion, thereby reducing power consumption.
2Measurement precision
If time-to-digital converters are used for high time resolution, then measurement precision is improved, but cost-efficiency deteriorates for high scanning rates
Solution Approach 1:
The patent segments the time measurement task into multiple coarse time intervals using the ramp signal, with each interval processed by a relatively simple time-to-digital converter. The high time resolution is achieved through the combination of multiple segmented measurements in the histogram, allowing the use of lower-cost TDCs that would individually provide insufficient resolution.
Solution Approach 2:
The patent merges multiple low-resolution time measurements from the time-to-digital converter into a high-resolution histogram through bin accumulation. By combining many individual measurements across multiple ramp cycles, the system achieves high effective time resolution using multiple modest-cost components rather than a single expensive high-resolution TDC.
3Productivity
If high scanning rates are implemented, then productivity is improved, but time jitter effects worsen
Solution Approach 1:
The patent uses periodic ramp signals with controlled durations to scan the analog input at high effective rates while maintaining stable timing references. By repeating the measurement process many times with identical periodic ramp waveforms, the system accumulates statistics that reveal and correct for systematic timing variations, reducing the impact of random time jitter on the final measurement precision.
Solution Approach 2:
The histogram block provides feedback by accumulating and analyzing timing measurements from multiple ramp cycles. This statistical feedback allows the system to identify and compensate for time jitter effects, as the histogram distribution reveals the impact of timing variations and enables correction through proper bin selection and weighting in the final measurement.
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
The solution enables cost-efficient and high-resolution digitization of analog signals from LIDAR measurements, reducing the impact of time jittering and enhancing scanning performance, thus providing a more efficient and affordable option for high-speed LIDAR applications.
Implementation Method 1
the first time-to-digital converter scans the analog signal based on a ramp signal, and delivers an output to the histogram block
Implementation Method 2
which, based thereon, generates a time-correlated histogram
Data Source
AI summary
Described herein are analog-to-digital converters (ADCs) that utilize time-to-digital converters (TDCs) and a histogram block to generate time-correlated histograms from analog signals. In some implementations, the time-to-digital converters determine time intervals for which the analog signal above or below a ramp signal, and the histogram block generates the time-correlated histograms of values using the determined time intervals. Furthermore, in some implementations, the analog-to-digital converters receive the analog signals from photodiodes, such as photo diodes used in Light Detection and Ranging (LIDAR) devices. In some such applications, the use of time intervals to generate time-correlated histograms may be used to reduce the effects of time jitter.