Rational Number Phase Filtering for Stable Synchronous Clocks
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Solution Overview
Problem
Existing phase noise reduction methods in timing referencing systems suffer from accumulation of quantization errors, leading to uncontrolled phase transients and increased costs due to the need for expensive voltage-controlled oscillators.
Innovation Solution
The use of rational numbers in phase filtering, specifically through the implementation of rational number filters (RNF) in open loop systems, prevents accumulation of quantization errors by utilizing integer parts for phase amendments and supplementing fractional parts, allowing for the production of a synchronous clock with improved stability and reduced costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional phase noise reduction methods are used, then phase noise filtering is achieved, but quantization errors accumulate causing uncontrolled phase transients
Solution Approach 1:
The patent segments the phase value into integer part and fractional part. The integer part is used for phase amendments while the fractional part is accumulated separately. This segmentation prevents quantization error accumulation by properly handling the fractional components that would otherwise be lost in conventional methods.
Solution Approach 2:
The patent implements a feedback mechanism where the fractional part of the phase difference is accumulated and fed back into the phase calculation for the next cycle. This feedback loop ensures that quantization errors are not discarded but rather incorporated into subsequent calculations, maintaining long-term phase accuracy.
2Object-affected harmful factors
If expensive voltage-controlled oscillators are used, then phase noise reduction is achieved, but system cost increases
Solution Approach 1:
The patent replaces expensive voltage-controlled oscillators with a combination of a stable crystal oscillator and digital signal processing. The digital phase measurement and rational number filter provide the necessary phase noise reduction at a fraction of the cost of VCXO-based solutions, using computationally efficient algorithms instead of expensive hardware.
Solution Approach 2:
The patent substitutes the mechanical/electrical phase control mechanism of voltage-controlled oscillators with a digital system using TDC, RNF, and DTC components. This substitution eliminates the need for expensive analog phase control hardware while achieving superior phase noise reduction through digital rational number filtering.
3Ease of manufacture
If free-running local clock is used, then cost is reduced, but phase noise and stability deteriorate
Solution Approach 1:
The patent introduces a rational number filter as an intermediary between the free-running local clock and the phase measurement system. This intermediary component filters out phase noise from the local clock while preserving its low-cost advantage, acting as a digital equivalent to expensive analog filtering components.
Solution Approach 2:
The patent changes the parameter representation from conventional fixed-point or floating-point numbers to rational numbers with limited denominators. This parameter change enables exact representation of phase relationships without quantization errors, improving the effective stability of the free-running clock system.
Data Source
AI summary
A Time Processing Technology (TPT) disclosed herein is contributing methods, systems and circuits for filtering out a phase noise of a timing referencing signal and producing a timing implementing signal from a free running local clock or its subclocks wherein the filtering out the phase noise is implemented with an open loop system (OLS) or a closed loop system (CLS) of phase control, wherein TPT comprises and is enabled by contributed herein a time to digital converter (TDC), a rational number filter (RNF) and a digital to time converter (DTC), securing improved resolution and open loop operations of phase control systems.