Microwave Motion Sensor Path Switching for DC Offset Elimination
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional microwave motion sensors using the Doppler principle face issues with sensing zero points and DC offset due to environmental clutters, leading to reduced sensitivity and detection failures.
Innovation Solution
The implementation of a microwave motion sensor architecture that includes a dual-control voltage-controlled oscillator and a path switching mechanism to eliminate sensing zero points and DC offset, utilizing a phase-locked loop and delay path switching to ensure continuous and stable detection by switching transmission/reception paths with different phase shifts and adjusting the DC level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If continuous wave radar is used for Doppler shift detection, then the sensor can continuously detect motion, but DC offset occurs due to co-frequency reflected wave from environmental clutters causing receiver saturation and reduced sensitivity
Solution Approach 1:
The patent employs periodic action by switching between multiple transmission paths with different phase shifts in a cyclic manner. The path switching device alternates between different paths (e.g., path 1, path 2, path 3) over time, allowing the system to periodically sample different phase configurations. This periodic switching enables the receiver to avoid continuous saturation from DC offset by distributing the signal across different time slots, while maintaining continuous detection capability through rapid sequential measurement.
2Device complexity
If single-frequency Doppler architecture is used, then the sensor architecture is simple, but sensing zero points occur periodically at quarter wavelength intervals where detection sensitivity is zero
Solution Approach 1:
The patent applies segmentation by dividing the transmission path into multiple distinct paths (path 1, path 2, path 3) with different phase characteristics. Each path can be independently controlled and switched, allowing the system to segment the overall detection function across multiple sub-paths. This segmentation enables the system to overcome the sensing zero point limitation of a single path by distributing measurement across multiple paths, where at least one path should have non-zero sensitivity at any given location.
Solution Approach 2:
The patent implements dynamics through the path switching device that can dynamically change the active transmission path based on detected conditions. The system transitions from a static single-path configuration to a dynamic multi-path switching architecture. The controller can switch between different paths in response to detection requirements, allowing the system to adapt to varying environmental conditions and avoid sensing zero points by dynamically selecting optimal paths.
3Measurement precision
If multiple transmission paths with different phase shifts are switched, then sensing zero points are eliminated, but the device complexity increases due to path switching components
Solution Approach 1:
The patent applies universality by designing the path switching device to perform multiple functions: it not only switches between different transmission paths but also introduces different phase shifts, controls signal timing, and coordinates with the receiver to eliminate sensing zero points. The same switching mechanism serves multiple purposes including path selection, phase modulation, and detection optimization, reducing the need for separate dedicated components 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
This solution enhances the stability and sensitivity of microwave motion sensor detection, preventing detection failures and reducing electromagnetic interference, while also lowering average transmission power and eliminating sensing zero points, thereby improving the reliability of detecting disturbances like heartbeat and vibrations.
Implementation Method 1
The path switching device is coupled to the signal processing device and the transmitting device and results in different phase shifts to a plurality of transmission paths which the microwave signal passes through
Implementation Method 2
When the signal transmitted from the sensor 100 hits the object under detection 110, the transmitted signal will be reflected as a reception signal
Implementation Method 3
Based on the Doppler principle, the microwave motion sensor compares the phase shift between the transmitted signal and the received signal. If phase shift occurs, this indicates that there is disturbance source in the environment
Data Source
AI summary
A microwave motion sensor including a transmitting device, a signal processing device, a signal processing device, and a path switching device is disclosed. The transmitting device transmits a microwave signal to a space under detection. The receiving device receives a reflected microwave signal reflected from the space under detection. The signal processing device processes the reflected microwave signal received by the receiving device to judge whether there is a disturbance in the space under detection, wherein the signal processing device generates the microwave signal. The path switching device is coupled to the signal processing device and the transmitting device and results in different phase shifts to a plurality of transmission paths travelled by the microwave signal.