MEMS Microphone Dual-Chip Subtractor Ultrasonic Interference
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Solution Overview
Problem
MEMS microphones suffer from poor anti-interference performance and sensitivity due to overloading from high-power ultrasonic transceivers, leading to noise generation across various frequency bands.
Innovation Solution
A MEMS microphone design incorporating two MEMS microphone chips with distinct frequency response droop characteristics, where the outputs from both chips are connected to a subtractor to eliminate ultrasonic frequency band signals, thereby enhancing anti-interference performance and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single MEMS microphone chip is used, then the device structure is simple, but the anti-interference performance is poor due to ultrasonic frequency overload
Solution Approach 1:
The single MEMS microphone chip is divided into two separate chips with different frequency response droop characteristics. The first chip has a droop characteristic of less than 1 kHz while the second chip has a droop characteristic of 1-30 kHz. This segmentation allows each chip to process different frequency ranges, and when their outputs are subtracted, ultrasonic interference signals are eliminated while preserving audible sound signals.
Solution Approach 2:
The invention changes the frequency response droop characteristic parameter of the MEMS microphone chips. By designing two chips with different droop characteristics (first chip: <1 kHz, second chip: 1-30 kHz), the system creates differential responses to ultrasonic frequencies versus audible frequencies. This parameter variation enables the subtractor to distinguish and eliminate ultrasonic interference while maintaining sensitivity to legitimate sound signals.
2Power
If high-power ultrasonic transceivers are used, then the transmission power is sufficient, but noise is generated in the MEMS microphone due to overloading
Solution Approach 1:
The invention converts the harmful effect of ultrasonic overload into a beneficial signal processing opportunity. By designing MEMS microphone chips with specific frequency response droop characteristics, the ultrasonic interference signals are captured but with attenuated amplitude due to the droop effect. When these signals are processed through the subtractor along with signals from the second chip, the ultrasonic components cancel each other out, transforming the previously harmful overload condition into an eliminable artifact.
Solution Approach 2:
The subtractor acts as an intermediary device that receives signals from both MEMS microphone chips and performs differential processing. This intermediary component enables the elimination of ultrasonic noise by subtracting the output of the second chip (with 1-30 kHz droop) from the first chip (with <1 kHz droop), while preserving the audible frequency signals that do not exhibit the same cancellation pattern.
3Measurement precision
If the MEMS microphone sensitivity is increased, then the sound pickup capability is improved, but the susceptibility to ultrasonic interference increases
Solution Approach 1:
The sensitive detection function is segmented across two MEMS microphone chips with different frequency response characteristics. The first chip maintains high sensitivity across the audible range with minimal droop (<1 kHz), while the second chip has pronounced droop (1-30 kHz) that attenuates ultrasonic frequencies. This segmentation allows the system to maintain high overall sensitivity while the differential processing eliminates ultrasonic susceptibility.
Solution Approach 2:
The invention applies parameter changes to the frequency response droop characteristic to decouple sensitivity from ultrasonic susceptibility. By setting the first chip's droop characteristic to less than 1 kHz and the second chip's droop characteristic to 1-30 kHz, the system creates a parameter difference that enables the subtractor to identify and eliminate ultrasonic interference while preserving sensitive detection of audible sounds.
Data Source
AI summary
The present invention provides a MEMS microphone, including a housing body with a containment space, a sound hole penetrating the housing body, a MEMS microphone chip, an ASIC chip and a subtractor accommodated in the containment space. The MEMS microphone chip includes at least a first MEMS microphone chip and a second MEMS microphone chip. the first MEMS microphone chip is different from the frequency response droop characteristic of the second MEMS microphone chip. the first MEMS microphone chip and the output signal of the second MEMS microphone chip are output to the subtractor, and are output to the ASIC chip after the subtractor performs subtraction processing. Compared with the related art, the MEMS microphone of the present invention has good anti-interference performance and good sensitivity.