Time-Interleaved Sampling With Random Skipping for Timing Skew
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Solution Overview
Problem
Time-interleaved analog-to-digital converters (TI ADCs) face issues due to mismatches between sub-ADCs, such as offset, gain, and timing mismatches, which lead to distortion, signal corruption, and require frequent recalibration, especially when the input signal does not meet certain stationarity conditions, limiting their applicability and efficiency.
Innovation Solution
A time-interleaved sampling system where samplers operate in a track mode and hold mode, with a predetermined sequence that includes random skipping of samplers, utilizing a random skip generation digital logic circuit to bypass samplers at random intervals, allowing the next sampler to enter the track mode, thereby reducing timing skew and improving signal fidelity without the need for continuous recalibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If traditional time-interleaved sampling is used, then high sampling rate is achieved, but timing skew and mismatch errors occur between sub-ADCs
Solution Approach 1:
The patent applies dynamics by making the sampling sequence flexible and adaptive rather than fixed. The system dynamically adjusts which sub-ADC samples at each time instant based on a randomization sequence, allowing the sampling assignment to change over time. This dynamic approach resolves the contradiction by accommodating timing skew variations while maintaining high overall sampling rate.
Solution Approach 2:
The patent changes the parameter of sampling assignment from a fixed deterministic sequence to a randomized sequence. By varying the assignment pattern over time through randomization, the system transforms the static timing skew problem into a manageable statistical issue that can be handled through averaging and calibration, thereby maintaining high sampling rate while improving timing accuracy.
2Measurement precision
If calibration is performed to correct mismatch errors, then measurement precision is improved, but system complexity and recalibration requirements increase
Solution Approach 1:
The patent applies preliminary action by performing calibration during periods when the ADC is not actively converting signal data. The randomization sequence is pre-generated and stored, allowing calibration to be conducted offline without interfering with normal operation. This resolves the contradiction by separating calibration activities from signal processing, reducing system complexity and recalibration overhead.
Solution Approach 2:
The system implements self-service through automated calibration procedures that use the randomized sampling sequence to automatically detect and correct mismatch errors without requiring external intervention. The calibration process is integrated into the normal operation flow, allowing the system to self-correct timing skew and gain/offset mismatches, thereby improving signal accuracy while minimizing calibration complexity.
3Measurement precision
If random sampling sequence is used, then timing skew effects are reduced, but hardware complexity increases
Solution Approach 1:
The patent applies periodic action by using a pseudorandom sequence that repeats after a fixed period. This periodicity allows the system to pre-generate and store the entire randomization sequence in a compact lookup table, eliminating the need for complex real-time random number generation logic. The timing skew reduction benefit is achieved while keeping hardware complexity low through this periodic approach.
Solution Approach 2:
The patent uses copying by storing a pre-generated pseudorandom sequence in a lookup table that can be repeatedly accessed. Instead of generating random numbers in real-time, the system copies from the pre-computed sequence, significantly simplifying the control logic while maintaining the timing skew reduction benefits of randomization.
4Measurement precision
If foreground calibration is used, then measurement precision is improved, but productivity decreases due to ADC unavailability
Solution Approach 1:
The patent applies continuity of useful action by enabling calibration to occur during normal ADC operation through background calibration methods. The randomized sampling sequence allows calibration measurements to be extracted from ongoing signal processing without interrupting the conversion function. This resolves the contradiction by maintaining continuous ADC availability for both signal conversion and calibration activities.
Data Source
AI summary
A time-interleaved sampling system includes an input signal having a time-varying analog value and a plurality of samplers. Each sampler is operable in a hold mode and a track mode. In the track mode, the samplers track the analog value of the input signal. In the hold mode, each sampler holds a respective analog value of the input signal that a respective sampler tracked immediately before entering the hold mode. The samplers enter the track mode in a predetermined sequence. After a last sampler in the predetermined sequence enters the track mode, the predetermined sequence is repeated in a loop. At random intervals, a skipped sampler in the predetermined sequence is bypassed from entering the track mode.