Ultrasonic Rangefinding with pMUT Array and Pulse-Echo
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Solution Overview
Problem
Existing gesture recognition systems for portable devices face challenges such as large size, high power consumption, and inability to operate in sunlight, and are susceptible to multipath interference due to their reliance on optical 3D imagers or continuous wave ultrasound signals.
Innovation Solution
A system using ultrasound waves with time diversity and a spatial array of transceivers to measure range and direction, employing pulse-echo excitation and phased array techniques to achieve low-power, compact, and sunlight-compatible gesture recognition, allowing for non-contact user input and environmental mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If optical 3D imagers are used for gesture recognition, then gesture control functionality is achieved, but the system size becomes large and power consumption increases
Solution Approach 1:
The patent replaces optical 3D imaging systems with ultrasonic transceivers that use acoustic waves instead of light. This substitution enables gesture recognition through sound wave propagation and echo detection, dramatically reducing power consumption from 12 watts to under 10 milliwatts while maintaining compact form factor suitable for portable devices
Solution Approach 2:
The invention changes the operating frequency parameter to ultrasonic ranges (above human hearing), allowing the system to operate at very low power levels. By using high-frequency acoustic waves with short wavelengths, the system achieves precise gesture detection while consuming minimal energy, resolving the contradiction between functionality and power consumption
2Ease of operation
If continuous wave ultrasound signals are used, then gesture detection is enabled, but multipath interference occurs and dynamic range requirements increase
Solution Approach 1:
The patent employs periodic pulsed ultrasound signals instead of continuous waves. By transmitting short bursts of ultrasonic energy followed by listening periods for echoes, the system eliminates multipath interference where reflected signals from multiple surfaces create destructive interference. The pulsed operation allows clear distinction between direct echoes and delayed reflections, significantly improving signal accuracy and reducing the dynamic range requirements of receive electronics
3Use of energy by moving object
If ultrasound waves are used for range measurement, then power consumption is reduced, but the system requires extremely high dynamic range in receive electronics
Solution Approach 1:
By using pulsed ultrasound transmission with carefully controlled duty cycles and time-gated reception, the system minimizes the presence of strong transmitted signals during echo detection periods. This temporal separation allows simple receive electronics to detect faint echoes without requiring extreme dynamic range, as the transmitter is inactive during measurement windows
Solution Approach 2:
The system performs preliminary signal processing including bandpass filtering and correlation detection before full echo analysis. By preprocessing the received signals to enhance echo characteristics and suppress noise early in the detection chain, the system reduces the dynamic range burden on subsequent amplification and ADC stages, enabling low-power operation with simpler electronics
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
Enables gesture control and environment mapping with low power consumption (<10 mW) and compact size (<1 cm3), effectively operating in various environmental conditions while minimizing multipath interference.
Implementation Method 1
an ultrasound wave is emitted from one or more ultrasound transceivers, and one or more ultrasound transceivers are used to detect the echo
Implementation Method 2
detect the echo
Implementation Method 3
Time diversity in the transmitted signal allows the time-of-flight to be calculated which is used to infer the range to the target
Implementation Method 4
A spatial array of transceivers allows the direction of the returning wave to be calculated
Implementation Method 5
employing pulse-echo excitation and phased array techniques
Data Source
AI summary
An apparatus for determining location of a moveable object in relation to an input device includes an array of one or more piezoelectric micromachined ultrasonic transducer (pMUT) elements and a processor. The array is formed from a common substrate. The one or more pMUT elements include one or more transmitters and one or more receivers. The processor configured to determine a location of a moveable object in relation to an input device using sound waves that are emitted from the one or more transmitters, reflected from the moveable object, and received by the one or more receivers.