Phase Alignment Circuitry for Jitter-Tolerant Audio Clock Recovery
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Solution Overview
Problem
In digital audio systems, maintaining phase alignment between the input clock signal and the output frame synchronization signal is crucial for accurate audio signal output. However, temporary losses or jitter in the input clock signal can lead to phase misalignment, resulting in audible deterioration of audio quality.
Innovation Solution
The phase alignment circuitry operates in multiple modes to align the phase of the output signal with the input clock signal. It determines the phase difference and applies correction steps, which can be of fixed duration, randomly selected, or pseudo-randomly positioned, to maintain or recover phase alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the input clock signal is used directly to generate the output frame synchronization signal, then the circuit complexity is low, but phase misalignment occurs when jitter or temporary loss happens
Solution Approach 1:
The phase alignment circuitry proactively monitors the phase relationship between input clock signal and output frame synchronization signal, and applies correction steps in advance to prevent phase misalignment from occurring. This preliminary action ensures reliable phase alignment even when jitter or temporary loss occurs, without requiring complex re-synchronization mechanisms.
Solution Approach 2:
The system continuously monitors the phase alignment status between the input clock signal and output frame synchronization signal, and uses this feedback information to dynamically adjust correction steps. This closed-loop feedback mechanism maintains reliable phase alignment while keeping the circuit complexity manageable through intelligent control rather than hardware redundancy.
2Measurement precision
If correction steps are applied frequently to maintain phase alignment, then phase alignment accuracy is improved, but audible artifacts such as pops may occur
Solution Approach 1:
The phase alignment circuitry applies correction steps selectively rather than continuously - only when phase misalignment exceeds a threshold. This partial action approach maintains sufficient phase alignment accuracy for high-quality audio output while avoiding excessive corrections that would generate audible artifacts such as pops.
Solution Approach 2:
The system dynamically adjusts the magnitude and timing of correction steps based on the detected phase error parameters. By changing these correction parameters adaptively rather than applying fixed corrections, the system achieves high phase alignment accuracy while minimizing the generation of audible artifacts.
3Reliability
If the period of output signal cycles is extended to correct phase difference, then phase alignment is recovered, but the audio signal timing is disrupted
Solution Approach 1:
The phase correction process is segmented into multiple small correction steps applied across successive output signal cycles, rather than applying one large correction that would disrupt audio timing. This segmentation allows phase alignment recovery while maintaining consistent audio signal timing throughout the correction process.
Solution Approach 2:
Correction steps are applied periodically to successive cycles of the output signal in a controlled manner. This periodic application of corrections distributes the phase adjustment over time, enabling phase alignment recovery without causing timing disruptions to the audio signal.
Data Source
AI summary
Circuitry for aligning a phase of an output signal with a phase of an input clock signal, the circuitry being operable in one of a plurality of phase alignment modes, wherein the plurality of phase alignment modes comprises two or more of: a single step alignment mode; a multiple step alignment mode; and a random or pseudo-random step alignment mode.