Digital high-pass filter for a displacement detection device of a portable apparatus
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Solution Overview
Problem
Existing digital high-pass filters for displacement detection in portable devices are complex, resource-intensive, and difficult to configure, leading to disparity in operation based on the initial position of the device and limited flexibility in detecting slow or fast user movements.
Innovation Solution
A digital high-pass filter with a recursive structure and adjustable cutoff frequency, implemented using a subtractor, recursive branch, integrator, and divider stages, which reduces the continuous component of acceleration signals due to gravity, allowing for independent displacement detection and easy configuration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a long time constant and high order high-pass filter is used to reduce the continuous component of acceleration signals, then the displacement detection becomes independent of the initial position, but the circuit complexity and resource usage become excessive
Solution Approach 1:
The patent implements a variable cutoff frequency that can be dynamically adjusted based on the detected movement type. The system switches between different cutoff frequency values to optimize filter performance for different movement scenarios, allowing effective displacement detection with reduced circuit complexity compared to a fixed high-order filter
Solution Approach 2:
The patent changes the filter parameter (cutoff frequency) adaptively based on the movement characteristics. By adjusting the cutoff frequency parameter rather than using a fixed high-order filter, the system achieves position-independent displacement detection with lower circuit complexity
2Adaptability or versatility
If a high-order high-pass filter is implemented to detect both slow and fast movements, then the detection coverage is improved, but the memory occupation and processing resources increase significantly
Solution Approach 1:
The system dynamically adjusts the cutoff frequency based on the type of movement detected, allowing a single filter structure to effectively handle both slow and fast movements by changing its frequency response characteristics, thereby reducing memory requirements compared to a fixed high-order filter
3Measurement precision
If a fixed high-pass filter with long time constant is used, then the continuous component due to gravity is reduced, but the filter cannot be easily reconfigured for different movement types
Solution Approach 1:
The patent implements a dynamic cutoff frequency that can be reconfigured based on the detected movement type. The system switches between different cutoff frequency values to optimize gravity component reduction for different movement scenarios, providing both effective filtering and adaptability
Solution Approach 2:
The system changes the filter parameter (cutoff frequency) adaptively based on movement characteristics, allowing the same filter structure to effectively reduce gravity components for different types of movements without requiring multiple fixed filters
Data Source
AI summary
A digital high-pass filter has an input, an output, and a subtractor stage, having a first input terminal, a second input terminal and an output terminal. The first input terminal of the subtractor stage is connected to the input of the digital high-pass filter and the output terminal is connected to the output of the digital high-pass filter. A recursive circuit branch is connected between the output of the digital high-pass filter and the second input terminal of the subtractor stage. Within the recursive circuit branch are cascaded an accumulation stage, constituted by an integrator circuit, and a divider stage. The cutoff frequency of the digital high-pass filter is variable according to a dividing factor of the divider stage.