Digital Phase Locked Loop Stabilization via Random Signal Cross-Correlation
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Solution Overview
Problem
The transfer function of digital phase locked loops is unstable due to changing phase locked loop gains caused by disturbances, and existing solutions either require increased hardware complexity or analog circuit consumption, failing to adapt to fluctuations in both phase detector and oscillator gains.
Innovation Solution
A method and device that stabilize the transfer function by feeding a random digital signal with predetermined variance into the phase locked loop, cross-correlating signals to estimate an impulse response, and adjusting loop filter gains based on this response to maintain a stable operating point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of quantization stages in the phase detector is increased to handle jitter, then the phase detector can cope with larger jitter values, but the hardware complexity and chip area increase significantly
Solution Approach 1:
The patent changes the parameter of the phase detector from a multi-stage quantization structure to a single-bit phase detector with a specific transfer characteristic. Instead of increasing quantization stages to handle jitter, the invention modifies the transfer function parameters to be insensitive to jitter, thereby maintaining reliability while reducing hardware complexity.
2Reliability
If analog circuits are added to adjust the phase detector gain, then the bandwidth and signal/noise ratio requirements can be met, but the chip area and energy consumption increase
Solution Approach 1:
The patent replaces analog circuits with digital signal processing techniques. Instead of using analog components to adjust phase detector gain, the invention uses a digital single-bit phase detector with a specifically designed transfer function that achieves the desired bandwidth and signal/noise ratio through digital means, eliminating the need for additional analog circuitry.
3Stability of the object's composition
If the phase locked loop gain is adjusted to stabilize the transfer function, then the operating point stability improves, but the system cannot adapt to simultaneous fluctuations in phase detector and oscillator gains
Solution Approach 1:
The patent employs feedback mechanisms where the single-bit phase detector continuously monitors the phase difference and adjusts the control signal to the oscillator. The feedback loop is designed with a transfer function that inherently compensates for gain fluctuations, allowing the system to maintain stability while adapting to changes in phase detector and oscillator gains through continuous real-time adjustment.
Data Source
AI summary
In a method for stabilizing a transfer function of a digital phase locked loop a random digital signal is fed into the phase locked loop. The phase locked loop comprises the transfer function and a phase locked loop gain which changes with time due to disturbances and the random digital signal comprises a predetermined variance. The transfer function depends from the phase locked loop gain. A cross correlation function is generated by cross correlating a signal of the phase locked loop with the random signal and an impulse response is estimated between the random signal and the signal of the phase locked loop by means of the cross correlation function and the predetermined variance of the random signal. The transfer function of the phase locked loop is set in dependence on the estimated impulse response.