Circular Vertical Hall Sensor Angle Precision via Quadrature Modulation
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Solution Overview
Problem
Existing magnetic field sensors using circular vertical Hall (CVH) sensing elements face challenges in accurately determining the angle of a magnetic field due to offset errors and limited resolution, which affects the precision of angle measurement.
Innovation Solution
A magnetic field sensor system comprising a CVH sensing element, an analog-to-digital converter, a quadrature modulator circuit, and a processor stage that performs an arctangent calculation using the CORDIC algorithm to compute the estimated angle of the external magnetic field, with noise shaping and sliding window integration techniques to enhance accuracy and resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a CVH sensing element is used to detect magnetic field angle, then the sensing capability is improved, but offset errors and limited resolution reduce measurement precision
Solution Approach 1:
The patent extracts and removes offset errors from the measurement system by performing separate offset calibration measurements and subtracting them from the final angle calculation. The offset errors are isolated and eliminated through the calculation: angle = arctan((Vy - Vyo)/(Vx - Vxo)), where Vxo and Vyo are the offset values removed from the signals.
Solution Approach 2:
The patent performs preliminary offset calibration measurements before the actual angle measurement. The offset values Vxo and Vyo are determined in advance through calibration procedures, allowing the main measurement to focus solely on the magnetic field angle without being affected by offsets.
2Measurement precision
If the angular spacing of vertical Hall elements is reduced to improve resolution, then more elements are required, increasing device complexity
Solution Approach 1:
The patent transitions from discrete angular sampling to continuous angular measurement by implementing signal processing in the quadrature domain. Instead of relying on the spatial arrangement of multiple Hall elements, the system uses I-Q modulation and arctangent calculation to achieve continuous angle resolution, effectively moving from a spatial dimension to a signal processing dimension.
Solution Approach 2:
The patent replaces the mechanical/spatial approach of using more densely packed Hall elements with an electronic signal processing approach. The continuous angle measurement is achieved through quadrature modulation and arctangent calculation rather than through increased spatial sampling density.
3Measurement precision
If signal processing techniques are added to improve accuracy, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent implements a universal signal processing framework using quadrature modulation that can handle offset errors, enhance resolution, and provide continuous angle measurement all through the same I-Q demodulation and arctangent calculation process. This multi-functional approach achieves multiple goals without requiring separate processing circuits for each function.
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
The system achieves improved accuracy and resolution in determining the angle of a magnetic field, surpassing the angular spacing of the vertical Hall elements, and allows for real-time updates of the estimated angle, enabling precise detection of magnetic field orientations.
Implementation Method 1
One type of current sensor uses a Hall effect magnetic field sensing element in proximity to a current-carrying conductor.
Data Source
AI summary
A magnetic field sensor includes a circular vertical Hall (CVH) sensing element to produce a signal representing an external magnetic field as detected by the CVH sensing element, a sigma-delta analog-to-digital converter to generate a converted signal, modulators to produce quadrature modulated signals from the converted signal, and a processor to produce an estimated angle of the external magnetic field using the quadrature modulated signals. An arctangent function may be used to calculate the estimated angle. A sliding window integration scheme may be used over one or more CVH cycles.