Passive Doppler Motion Detection System
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Solution Overview
Problem
Existing radiofrequency sensing systems for detecting motion in home and office environments suffer from high error rates due to complex and error-prone amplitude monitoring, leading to false positive or negative results, which disrupt network device functions.
Innovation Solution
A detection system utilizing at least two devices that send and receive radiofrequency signals, employing passive Doppler sensing based on the known sending signal frequency to accurately detect motion by analyzing reflections of the sent signal, thereby reducing the complexity of determining the sending signal frequency from the received signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radiofrequency sensing is used for detecting motion by monitoring amplitude of exchanged messages, then motion detection capability is provided, but detection accuracy deteriorates due to complex and error-prone monitoring process
Solution Approach 1:
The patent replaces the complex mechanical/amplitude-based monitoring system with a Doppler effect-based detection system. Instead of monitoring message amplitudes to detect motion, the system uses radiofrequency signals that reflect off moving subjects, causing frequency shifts detectable through Doppler sensing. This substitution of the detection mechanism fundamentally simplifies the process while improving accuracy, as the Doppler effect provides direct information about subject motion without requiring complex amplitude analysis.
Solution Approach 2:
The patent changes the detection parameter from amplitude monitoring to frequency shift detection. By monitoring the frequency changes in reflected radiofrequency signals rather than the amplitude of exchanged messages, the system achieves more reliable motion detection. The frequency parameter provides direct information about subject velocity and motion state, making the detection process more accurate and less error-prone than amplitude-based methods.
2Reliability
If amplitude monitoring is used to detect motion, then motion detection is enabled, but error rate increases leading to false positive or negative results
Solution Approach 1:
The patent replaces the unreliable amplitude monitoring mechanism with a Doppler-based frequency shift detection system. The Doppler effect provides a more reliable and precise indicator of motion, as frequency shifts are directly proportional to subject velocity and are less susceptible to environmental interference and signal variations that plague amplitude-based methods.
Solution Approach 2:
The patent implements a feedback mechanism where the known sending signal frequency is used as a reference to detect and measure the frequency shifts in reflected signals. This feedback approach allows the system to accurately determine motion by comparing the reflected frequency against the original frequency, enabling precise calculation of subject velocity and improving overall detection accuracy while reducing false positives and negatives.
3Loss of information
If sending signal frequency is determined from received radiofrequency signal, then frequency information is obtained, but detection complexity and error probability increase
Solution Approach 1:
The patent applies preliminary action by establishing and storing the sending signal frequency before the detection process begins. Instead of determining the frequency from the received signal during operation, the system pre-establishes the reference frequency and uses it for Doppler calculations. This preliminary setup eliminates the need for complex frequency determination algorithms during runtime, reducing both computational complexity and potential errors while ensuring accurate frequency information is always available for comparison.
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 enhances the accuracy of motion detection, differentiates between various subjects and their behaviors, and reduces the influence of vibrations and noise, improving the reliability of motion detection in radiofrequency sensing systems.
Implementation Method 1
a detection unit for detecting motion of the subject by performing a passive Doppler sensing based on the received radiofrequency signal and the provided sending signal frequency
Implementation Method 2
receiving a radiofrequency signal that is indicative of reflections of the sent radiofrequency signal of the subject
Data Source
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AI summary
:The invention relates to a detection system for detecting motion of a subject by utilizing at least two devices adapted to send and receive radiofrequency signals. The system (110) comprises a control unit (111) for controlling the at least two devices such that at least one of the at least two devices is a sending device (120) sending a radiofrequency signal with a sending signal frequency and such that at least one of the at least two devices is a receiving device (130) receiving a radiofrequency signal that is indicative of reflections of the sent radiofrequency signal of the subject, a signal frequency providing unit (112) for providing the sending signal frequency with which the radiofrequency signal has been sent, and a detection unit (113) for detecting motion of the subject by performing a passive Doppler sensing based on the received radiofrequency signal and the provided sending signal frequency.