PLL Oscillator Threshold Tuning for Spurious Oscillation Detection
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Solution Overview
Problem
Conventional oscillator circuits face challenges in accurately detecting and adjusting for spurious oscillations, which occur less frequently than main oscillations, leading to insufficient detection accuracy due to the difficulty in setting frequency determination thresholds.
Innovation Solution
An oscillator circuit incorporating a phase locked loop (PLL) circuit that adjusts the ratio between the first and second oscillation frequencies and uses loop filter voltages to control the oscillator, allowing for precise adjustment of thresholds to detect and manage both main and spurious oscillations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frequency determination threshold is adjusted while spurious oscillation is actually reproduced for each individual, then detection accuracy of spurious oscillation is improved, but it becomes difficult to adjust the threshold because spurious oscillation occurs less frequently
Solution Approach 1:
The patent applies preliminary action by adjusting the frequency determination threshold in advance during manufacturing or initialization, rather than waiting for spurious oscillation to occur naturally. The control unit stores multiple threshold values and selects appropriate ones based on resonator characteristics, eliminating the need to wait for rare spurious oscillation events to perform adjustments.
Solution Approach 2:
The patent uses copying by creating a model or simulation of spurious oscillation conditions through the PLL circuit generating artificial oscillation signals. This allows threshold adjustment without requiring actual spurious oscillation to occur, as the system copies the essential characteristics of spurious oscillation for calibration purposes.
2Device complexity
If conventional oscillator circuits wait for spurious oscillation to occur before detection, then the system remains simple, but detection accuracy becomes insufficient due to infrequent occurrence
Solution Approach 1:
The patent implements feedback by using the PLL circuit to continuously monitor oscillation frequencies and compare them against stored threshold values. The control unit receives feedback from the frequency detection unit and automatically adjusts control signals to the oscillator, enabling accurate detection without complex manual intervention while maintaining system simplicity.
Solution Approach 2:
The system applies self-service by enabling the oscillator circuit to automatically detect and correct spurious oscillation conditions using pre-stored threshold values. The control unit autonomously selects appropriate thresholds based on resonator characteristics and performs adjustments without requiring external intervention, improving detection accuracy while maintaining operational simplicity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables high-accuracy detection and control of oscillator circuits, allowing for stable operation even with resonators prone to spurious oscillations, thereby improving detection accuracy and maintaining oscillation in the main oscillation mode.
Implementation Method 1
a phase locked loop (PLL) circuit, adjusting a ratio between a first frequency of the first oscillation signal and a second frequency of a second oscillation signal output from a voltage controlled oscillator, and controlling the oscillator based on a loop filter voltage being an input voltage of the voltage controlled oscillator
Implementation Method 2
a voltage controlled oscillator, outputting the second oscillation signal
Data Source
AI summary
An oscillator circuit includes: an oscillator, oscillating a resonator and generating a first oscillation signal; and a PLL circuit, adjusting a ratio between a first frequency of the first oscillation signal and a second frequency of a second oscillation signal output from a voltage controlled oscillator, and controlling the oscillator based on a loop filter voltage being an input voltage of the voltage controlled oscillator.