DPLL Cycle Slip Detection for Fast Phase Relocking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Digital phase-locked loops (DPLLs) face challenges in quickly relocking the phase of the output clock to the reference clock after a cycle slip event, which can take a long period of time, leading to phase difference wrapping around from 2π to 0, causing instability and prolonged relocking times.
Innovation Solution
Incorporation of a cycle slip detector circuit that immediately detects cycle slips and adjusts the digital output value by an integer multiple of the reference clock period, enabling immediate correction and preventing phase difference wrapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If a conventional DPLL is used without a cycle slip detector, then the device complexity is reduced, but the relocking time after a cycle slip event becomes excessively long
Solution Approach 1:
The cycle slip detector circuit continuously monitors the digital output value from the TDC and detects cycle slip events before they cause prolonged phase wrapping. By performing preliminary detection and immediate correction using the threshold comparison mechanism, the system prevents the accumulation of large phase differences, thereby reducing relocking time without requiring complete system redesign
Solution Approach 2:
The cycle slip detector circuit acts as an intermediary component between the TDC and the filter/VCO. It intercepts the digital output value, detects cycle slips through threshold comparison, and applies corrective adjustments before the signal proceeds to the filter. This intermediary function enables rapid correction of phase errors without disrupting the overall DPLL architecture
2Stability of the object's composition
If the phase difference is allowed to wrap around from 2π to 0 without detection, then the device operation is simpler, but the phase stability deteriorates
Solution Approach 1:
The cycle slip detector implements a feedback mechanism by continuously monitoring the digital output value from the TDC and comparing it against predefined thresholds. When a cycle slip is detected through this feedback loop, the system immediately applies corrective adjustment to the digital output value, preventing phase instability without requiring complex phase unwrapping algorithms or additional feedback paths
Solution Approach 2:
The system changes the parameter of the digital output value by applying an integer multiple adjustment when a cycle slip is detected. This parameter change corrects the phase error by shifting the digital output value by the appropriate number of clock periods, thereby maintaining phase stability through dynamic parameter adjustment rather than static design constraints
3Measurement precision
If cycle slip detection and correction is implemented, then the measurement precision of phase difference is improved, but the device complexity increases
Solution Approach 1:
The cycle slip detector uses partial action by implementing only the essential threshold comparison and correction functionality needed to detect and correct cycle slips. Rather than implementing a complete phase unwrapping system or complex analysis, the detector performs the minimum necessary action (comparing digital output against thresholds and applying integer corrections) to maintain measurement precision while minimizing added complexity
Data Source
AI summary
A digital phase-locked loop (DPLL) includes a voltage-controlled oscillator to generate an output clock, a filter coupled to the voltage-controlled oscillator, and a time-to-digital converter (TDC) that receives a reference clock and a feedback clock. The feedback clock is derived from the output clock. The TDC generates a digital output value. The DPLL also includes a cycle slip detector circuit coupled to the TDC. The cycle slip detector circuit detects a cycle slip based on the digital output value and adjusts the digital output value by a second digital value that corresponds to an integer multiple of a period of the reference clock.