Angular Velocity Sensor PLL Circuit Phase Noise Reduction
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Solution Overview
Problem
Conventional angular velocity sensors suffer from noise interference due to phase jitter in the detecting-phase timing signal, leading to inaccurate angular velocity detection, and are susceptible to temperature-induced signal offsets.
Innovation Solution
The angular velocity sensor employs a PLL circuit with a constant voltage source and a timing switching unit to generate a start-up mode signal when the amplitude is below a threshold, and uses a temperature correction processor to adjust signals based on ambient temperature, ensuring stable output characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a PLL circuit with fixed frequency clock signal is used for synchronous detection, then the circuit structure is simplified, but phase jitter occurs causing noise in the sensor output
Solution Approach 1:
The patent applies dynamics by making the clock signal frequency adaptive rather than fixed. The clock signal generation circuit adjusts the frequency of the clock signal based on the actual vibration frequency of the sensor element, allowing the system to dynamically track frequency changes while maintaining synchronous detection capability, thereby eliminating phase jitter without increasing circuit complexity
Solution Approach 2:
The patent implements feedback by using the monitor signal from the sensor element to generate a clock signal whose frequency is determined by the actual vibration characteristics. This feedback mechanism ensures that the clock signal remains synchronized with the sensor element's vibration, preventing phase errors and resulting noise in the output
2Measurement precision
If synchronous detection is performed with the driving frequency, then the undesired signal is removed, but temperature changes cause signal offsets
Solution Approach 1:
The patent uses feedback by continuously monitoring the vibration frequency through the monitor electrode and adjusting the clock signal frequency accordingly. This closed-loop approach ensures that synchronous detection remains accurate despite temperature-induced frequency drift, maintaining detection precision without requiring additional temperature compensation hardware
Solution Approach 2:
The patent applies parameter changes by allowing the clock signal frequency to vary based on the actual vibration frequency of the sensor element. This frequency adaptation compensates for temperature effects on the vibration characteristics, maintaining accurate synchronous detection across different temperature conditions
3Measurement precision
If the sensor element vibrates at constant amplitude, then the detection sensitivity is maximized, but the system becomes sensitive to amplitude variations due to temperature
Solution Approach 1:
The patent applies dynamics by making the system adaptive to amplitude variations through frequency tracking. Rather than attempting to rigidly maintain constant amplitude, the system dynamically adjusts the clock signal frequency to match the actual vibration frequency, maintaining detection sensitivity even when amplitude varies due to temperature effects
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 configuration reduces phase noise and maintains accurate angular velocity detection across varying temperatures, enhancing the sensor's stability and reliability for applications like attitude control and navigation systems.
Implementation Method 1
Monitor electrode 203 outputs an electric charge responsive to amplitude of the vibration
Implementation Method 2
When an angular velocity is applied to sensor element 201, sensor electrode 204 outputs an electric charge corresponding to a Coriolis force
Implementation Method 3
The PLL circuit in timing control circuit 206 produces an output after reducing the jitter noise existing as a phase error by multiplying the multi-bit signal and integrating the jitter noise in time domain
Data Source
AI summary
An angular velocity sensor including a vibration body having a sensor electrode, a driving electrode, and a monitor electrode. The monitor electrode generates a signal according to vibration of the vibration body. The sensor circuit outputs a signal representing an angular velocity applied to the vibration body. The amplitude determination circuit measures amplitude of vibration of the vibration body. A PLL circuit includes a constant voltage source for generating a constant voltage, a timing switching unit for outputting a voltage by switching selectively between the constant voltage and a voltage corresponding to the monitor signal, and a voltage-controlled oscillator for outputting an oscillation signal having a frequency corresponding to the voltage output from the timing switching unit. When the amplitude measured is smaller than a predetermined value, the timing switching unit outputs the constant voltage output from the constant voltage source and outputs a start-up mode signal.