Adaptive ADC Sampling Clock Control for Higher SFDR
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Solution Overview
Problem
Analog-to-Digital Converters (ADCs) introduce spurious products and noise that are deterministically related to the ratio of the input signal frequency and the sample clock, leading to suboptimal performance in certain frequency regions, and existing solutions require additional signal processing or conversion stages to mitigate these issues.
Innovation Solution
A control circuit that dynamically tunes the ADC sample clock to maintain a predetermined ratio between the sample clock frequency and the center frequency of the analog RF signal, using a tunable clock source and spectrum monitoring circuit to optimize spurious and noise performance across a wide band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed sampling rate is used in ADC, then the device complexity is reduced, but the spurious-free dynamic range (SFDR) deteriorates in certain frequency regions
Solution Approach 1:
The patent implements dynamic sampling rate adjustment by replacing the fixed sampling clock with a tunable clock source that can be adjusted based on the input signal frequency. The control circuit dynamically selects optimal sampling rates from a set of predefined rates to maintain favorable SFDR performance across different operating conditions, thus applying the dynamics principle to resolve the contradiction between fixed simplicity and variable performance.
Solution Approach 2:
The patent changes the sampling rate parameter adaptively based on the input signal characteristics. By monitoring the input frequency and selecting appropriate sampling rates from multiple available rates, the system optimizes the ratio between input frequency and sampling rate to minimize spurious products. This parameter change approach allows the ADC to maintain high SFDR performance without requiring additional conversion stages.
2Measurement precision
If additional signal processing circuits are added to suppress noise and spurious signals, then the spurious-free dynamic range is improved, but the device complexity increases
Solution Approach 1:
The patent applies preliminary action by optimizing the sampling rate before the ADC conversion process to prevent spurious products from being generated in the first place. By selecting the optimal sampling rate based on the input signal frequency, the system avoids the need for subsequent noise suppression circuits. This preventive approach resolves the contradiction by achieving high SFDR through proactive parameter optimization rather than reactive signal processing.
Solution Approach 2:
The patent implements a feedback mechanism where the input signal frequency is monitored and used to control the sampling rate selection. The control circuit receives information about the input frequency and adjusts the sampling clock accordingly to maintain optimal performance. This closed-loop feedback system achieves high SFDR performance through intelligent control rather than additional processing stages, resolving the contradiction between performance and complexity.
3Measurement precision
If the sampling clock frequency is dynamically adjusted to optimize SFDR, then the spurious-free dynamic range is improved, but the device complexity increases due to tunable clock source and control circuit
Solution Approach 1:
The patent applies universality by designing a control circuit that performs multiple functions: it monitors the input signal frequency, determines the optimal sampling rate, and generates the appropriate clock signal. This multi-functional approach consolidates what could be separate complex components into a single integrated control unit, achieving high SFDR performance while minimizing the increase in overall device complexity.
Solution Approach 2:
The patent introduces an intermediary control circuit that acts as a mediator between the input signal and the ADC. This control circuit processes the frequency information and generates the appropriate sampling clock, serving as an intelligent intermediary that optimizes performance without requiring complex additional processing stages. The intermediary approach resolves the contradiction by using a relatively simple control mechanism to achieve significant performance improvements.
Data Source
AI summary
A control circuit for signal sampling of an analog RF signal includes: a spectrum monitoring circuit for monitoring the analog RF signal to determine a frequency of the analog RF signal; a tunable clock source for generating a tunable sampling clock for sampling the analog RF signal; a sample clock tuning circuit for controlling the tunable clock source and selecting a sample clock frequency of the tunable sampling clock that provides a predetermined ratio between the sample clock frequency of the tunable sampling clock and a center frequency of the analog RF signal; and an Analog-to-Digital Converter (ADC) for sampling the analog RF signal using the tunable sampling clock.