Microwave Motion Detector Cross-Correlation Noise Cancellation
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Solution Overview
Problem
Microwave motion detectors face challenges in achieving high signal-to-noise ratios and enlarging detection areas without increasing power consumption, often missing alarms for weak signals and being sensitive to noise and limited signal strength.
Innovation Solution
The implementation of cross-correlation processing methods for IF signals, using two identical amplifier/analog-to-digital converter strings and a digital signal processor to reduce noise and enhance sensitivity, allowing for larger detection areas with reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the IF processing module amplifies and processes the IF signal, then the signal can be detected and processed, but noise is added to the signal which reduces detection sensitivity for weak signals
Solution Approach 1:
The patent creates a copy of the IF signal path by splitting the IF signal into two identical paths. Each path is processed independently through identical amplifier/analog-to-digital converter strings. The copied paths are then combined through cross-correlation processing to cancel noise while preserving the signal, thereby improving detection sensitivity without adding excessive noise.
2Measurement precision
If the microwave sensor radiates higher power to improve signal strength, then detection sensitivity improves, but power consumption increases which is problematic for battery-powered detectors
Solution Approach 1:
The patent uses signal path copying and cross-correlation to extract weak signals from noise without requiring high transmission power. By creating identical copies of the signal path and processing them in parallel, the system can detect weak signals from low-power microwave transmission, thereby maintaining detection sensitivity while reducing power consumption for battery-powered detectors.
Solution Approach 2:
The patent changes the processing parameters by using cross-correlation processing instead of traditional single-path amplification. This parameter change allows the system to achieve high detection sensitivity with lower input signal strength, enabling reduced microwave transmission power while maintaining effective detection range.
3Reliability
If traditional single-path IF signal processing is used, then the device complexity is low, but the signal-to-noise ratio is poor leading to missed alarms for weak signals
Solution Approach 1:
The patent segments the IF signal processing into two identical independent paths, each with its own amplifier and analog-to-digital converter. This segmentation allows independent noise cancellation through cross-correlation, improving alarm detection reliability for weak signals while maintaining manageable device complexity through modular design.
Solution Approach 2:
The patent implements a copied signal path architecture where the IF signal is duplicated and processed through identical chains. This copying approach improves reliability by enabling noise cancellation through comparison, while the modular copied structure keeps device complexity manageable through repetition of proven design blocks.
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 significantly improves signal-to-noise ratios and detection sensitivity, reduces false alarms, and allows for a larger detection area while maintaining low power dissipation, effectively addressing the limitations of prior art microwave motion detectors.
Implementation Method 1
If there is a person walking in the monitored area, then the detection module detects the frequency difference between transmitted and received microwaves
Implementation Method 2
cross-correlation processing of two IF signals from two identical amplifier/analog-to-digital converter strings
Data Source
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AI summary
A motion detector includes a microwave-based module to detect movement. Intermediate processing circuitry is coupled to an output from the module. The processing circuitry is activated intermittently to produce first and second pulsed output signals. Cross-correlation circuitry processes the two signals to produce a motion indicating output signal.