Gyroscope Phase-Locked Loop With Duty-Cycle Noise Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional phase-locked loops in gyroscopes are vulnerable to low-frequency jitter caused by noise, which is converted to duty-cycle error and phase noise, limiting their performance and stability.
Innovation Solution
A phase- and duty-cycle-locked loop system that operates on both edges of the clock, using a phase-frequency detector to compare clock edges and infer duty-cycle errors, which are then corrected by an integrator, thereby eliminating low-frequency noise and improving noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a conventional phase-locked loop uses a single edge of the reference clock for phase comparison, then the circuit implementation is simple, but the system becomes vulnerable to low-frequency jitter and phase noise
Solution Approach 1:
The patent segments the phase comparison operation into two separate processes: one for phase locking using rising edges, and another for duty-cycle correction using falling edges. This segmentation allows each process to optimize for its specific function while avoiding the noise vulnerabilities of conventional single-edge comparison
Solution Approach 2:
The patent introduces an intermediary duty-cycle correction path that processes falling edges separately from the main phase-locked loop. This intermediary path measures duty-cycle errors and generates correction signals that are applied to the reference clock, thereby eliminating low-frequency jitter before it can affect the phase comparison process
2Measurement precision
If conventional duty-cycle correction methods directly monitor the duty cycle by averaging high and low times, then duty-cycle errors can be corrected, but low-frequency noise is added by the measuring circuit
Solution Approach 1:
The patent extracts the duty-cycle measurement function from the main phase comparison path by using falling edges separately. This extraction allows duty-cycle correction to occur independently without introducing noise into the primary phase-locked loop operation
Solution Approach 2:
The patent employs periodic sampling of duty-cycle errors at each falling edge of the reference clock, rather than continuous averaging. This periodic action reduces low-frequency noise by only measuring at specific, well-defined moments in the clock cycle
3Object-affected harmful factors
If additive noise is converted to duty-cycle error and then to phase noise, then the noise performance degrades, but using a smaller footprint circuit is desired
Solution Approach 1:
The patent makes the phase-frequency detector multi-functional by enabling it to process both rising edges for phase locking and falling edges for duty-cycle correction. This universality eliminates the need for separate measurement circuits, achieving noise reduction without increasing circuit footprint
Data Source
AI summary
A system and method in accordance with the present invention provides a gyroscope incorporating an improved PLL technique. The improved PLL auto-corrects its own reference low-frequency noise, thereby eliminating this source of noise, improving the noise performance of the gyroscope and allowing a compact implementation. The net result is a gyroscope with improved bias stability that can meet noise requirements with a smaller footprint.