Ultrasonic Digital Microphone With Segmented Sigma-Delta Modulator
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Solution Overview
Problem
Conventional digital microelectromechanical microphones face inefficiencies in detecting ultrasonic signals due to high power consumption and degraded signal-to-noise ratio, especially when processing narrow-band ultrasonic signals, as they often require increasing clock frequencies beyond what is necessary for meaningful information frequencies.
Innovation Solution
A digital microelectromechanical microphone is designed with a band-pass sigma-delta modulator to process ultrasonic signals independently from audible signals, using separate clock frequencies and noise shaping to reject quantization noise, allowing for configurable detection of ultrasonic signals and reducing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the clock frequency of the A/D converter is increased to extend the noise shaping range to ultrasonic frequencies, then the detection capability for ultrasonic signals is improved, but the power consumption increases significantly
Solution Approach 1:
The patent divides the signal processing into separate paths: a first A/D converter with first clock frequency for audible signals, and a second A/D converter with second clock frequency for ultrasonic signals. This segmentation allows each converter to operate at optimized frequencies, preventing the need to increase the clock frequency of all converters to handle ultrasonic signals, thus reducing overall power consumption while maintaining ultrasonic detection capability.
2Measurement precision
If the clock frequency of the A/D converter is increased to improve noise shaping for ultrasonic signals, then the signal-to-noise ratio for ultrasonic signals is improved, but a large portion of the increased clock frequency is not applied to frequencies that carry meaningful information
Solution Approach 1:
The patent segments the noise shaping function into two independent A/D converters, each optimized for their respective frequency ranges. The first converter handles audible frequencies with appropriate noise shaping, while the second converter handles ultrasonic frequencies with its own noise shaping. This eliminates the inefficiency of applying high clock frequencies across the entire spectrum when only a narrow ultrasonic band requires enhanced noise shaping.
3Use of energy by moving object
If the clock frequency is limited to maximum available frequency, then the power consumption is reduced, but the signal-to-noise ratio significantly degrades for high-frequency ultrasonic signals
Solution Approach 1:
The patent uses two separate A/D converters with different clock frequencies optimized for their respective frequency ranges. The first converter operates at a lower clock frequency suitable for audible signals, while the second converter operates at a higher clock frequency specifically for ultrasonic signals. This segmentation allows the system to maintain acceptable power consumption while achieving adequate signal-to-noise ratio for ultrasonic detection.
Solution Approach 2:
The patent changes the clock frequency parameter differently for different signal bands. Instead of using a single high clock frequency for all signals, it applies a lower clock frequency to the first A/D converter for audible signals and a higher clock frequency to the second A/D converter for ultrasonic signals. This parameter differentiation optimizes both power consumption and signal-to-noise ratio for each frequency range.
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 enables efficient and accurate detection of ultrasonic signals with improved signal-to-noise ratio and reduced power consumption, allowing for always-on operation and flexible integration into various systems.
Implementation Method 1
an electro-acoustic sensor that can receive an acoustic signal including an ultrasonic signal and can generate an electric output signal representative of the acoustic signal
Implementation Method 2
a band-pass sigma-delta modulator that can receive the second electric output signal and can generate a digital output signal representative of the ultrasonic signal
Data Source
AI summary
Detection of audible and ultrasonic signals is provided by a microelectromechanical microphone. The detection range of ultrasonic signals can be configurable. In certain embodiments, the microelectromechanical microphone can include a band-pass sigma-delta modulator that can generate a digital signal representative of an ultrasonic signal. In addition or in other embodiments, the microelectromechanical microphone can include an event detector device that can determine that an ultrasonic event has occurred and, in response, can send a control signal to an external device. Detection of ultrasonic signals can be utilized in vehicular applications and/or gesture recognition.