Ultrasonic Proximity Detection Using Doppler Shift
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Solution Overview
Problem
Conventional proximity sensors in electronic devices, such as mobile phones, are bulky and increase manufacturing costs due to the need for additional components, and they may not accurately detect fast movements or reliably track objects at longer distances, leading to potential false-positive detections and increased bill of materials.
Innovation Solution
The use of ultrasonic sine-wave signals to detect movement based on Doppler shift, allowing the device to determine when to enable or disable touch or touchless input by inferring the presence or absence of objects through frequency shifts, utilizing existing acoustic transducers to avoid additional hardware and improve signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional proximity sensors (infrared) are used to detect user's head proximity, then proximity detection function is achieved, but bill of materials increases and device space is consumed
Solution Approach 1:
The patent reuses existing acoustic transducers (microphones and speakers) for dual purposes: their primary function for audio processing and an additional function for proximity detection via ultrasonic signal transmission and reception. This eliminates the need for dedicated infrared proximity sensors, reducing bill of materials and device complexity while maintaining proximity detection reliability
Solution Approach 2:
The device uses its own existing acoustic components to perform proximity detection, making the system self-sufficient. The microphones and speakers already present in the device are leveraged to transmit and receive ultrasonic signals, eliminating the need for external or additional specialized sensors
2Measurement precision
If conventional infrared proximity sensors are used, then proximity detection is provided, but detection accuracy for fast movements is insufficient
Solution Approach 1:
The patent employs continuous ultrasonic signal transmission and dynamic Doppler shift analysis to track moving objects in real-time. This dynamic approach allows the system to accurately detect fast movements by continuously monitoring frequency shifts, unlike static or periodically sampling infrared sensors that may miss rapid changes in position
Solution Approach 2:
The system uses Doppler shift feedback from reflected ultrasonic signals to continuously update information about object motion. By analyzing the frequency shift of reflected signals, the system receives real-time feedback about the velocity and direction of moving objects, enabling accurate tracking of fast movements
3Reliability
If conventional infrared proximity sensors are used, then basic proximity detection is achieved, but detection reliability at longer distances deteriorates
Solution Approach 1:
The patent changes the detection parameter from infrared light reflection to ultrasonic wave Doppler shift. Ultrasonic waves have longer wavelengths than infrared light, enabling them to travel farther and maintain detectable signal strength at longer distances. The Doppler shift measurement provides reliable detection information even when objects are at greater distances from the device
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 provides reliable detection of object movement, reduces manufacturing costs by reusing existing transducers, and offers better accuracy and reliability in disabling or enabling touch inputs, especially during phone calls, by continuously transmitting ultrasonic signals and processing frequency differences.
Implementation Method 1
The electronic device detects movement of an object beyond the device, such as movement of the user's head towards or away from the device, based on the phenomenon of Doppler shift in the reflections of the ultrasonic sine-wave signal from the object back to the device
Data Source
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AI summary
An electronic device (1) such as a cell phone, or a proximity detector for an electronic device (1), has an ultrasound transmitter (5), an ultrasound receiver (6), and a processing system. It transmits an ultrasonic sine-wave signal from the transmitter (5), and receives the ultrasonic sine-wave signal, through air, at the receiver (6). It detects when the frequency of the transmitted signal and a frequency of the received signal satisfy a predetermined difference criterion, and uses this to determine whether to disable or enable a touch or touchless input (2) on the device (1).