Digital Microphone Gain Control for Wide Dynamic Range
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Solution Overview
Problem
Digital MEMS microphones face challenges in maintaining Signal-to-Noise Ratio (SNR) characteristics and expanding their dynamic range, especially when processing low sound pressure signals, due to fixed amplification gains that limit their ability to handle wide dynamic ranges.
Innovation Solution
A microphone driving device with an analog amplification unit, an analog-to-digital converter, a digital amplification unit, and a gain controller, which includes voltage-to-current and current-to-voltage converters, allows for adaptive gain control based on sound pressure levels, ensuring constant amplification gain across varying sound pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If fixed amplification gain is used in ASIC, then the microphone can handle high sound pressure signals within maximum input range, but SNR characteristic deteriorates when low sound pressure signals are applied
Solution Approach 1:
The patent implements dynamic gain control by switching between normal and adjustment voltage-to-current converters based on sound pressure levels. The gain control signal dynamically adjusts which converter is active, enabling the system to adapt amplification gain to varying input conditions rather than using a fixed gain setting.
Solution Approach 2:
The patent changes the amplification gain parameter based on input signal characteristics. By switching between different voltage-to-current converter configurations, the system modifies the gain parameter to match the sound pressure level, improving SNR for low signals while maintaining compatibility with high sound pressure inputs.
2Device complexity
If normal voltage-to-current converter is used alone, then the circuit is simple, but the dynamic range is limited and cannot process signals above 130 dBSPL effectively
Solution Approach 1:
The patent divides the voltage-to-current conversion function into two separate converters: a normal voltage-to-current converter for standard conditions and an adjustment voltage-to-current converter for high sound pressure conditions. This segmentation allows each converter to be optimized for specific ranges, expanding the overall dynamic range while keeping individual converter designs relatively simple.
Solution Approach 2:
The patent creates a multi-functional voltage-to-current conversion system where two converters work in parallel under different conditions. The normal converter handles standard sound pressure levels while the adjustment converter handles high sound pressure levels, making the system universally capable of processing a wide range of input signals.
3Adaptability or versatility
If adjustment voltage-to-current converter is always active, then high sound pressure signals can be processed, but noise influence increases at low sound pressure levels
Solution Approach 1:
The patent dynamically controls the activation state of the adjustment voltage-to-current converter based on the sound pressure level of the input signal. The gain control signal switches the adjustment converter on for high sound pressure signals and off for low sound pressure signals, preventing noise contamination in sensitive low-level measurements.
Solution Approach 2:
The system uses feedback from the input signal level to control the operation of the adjustment voltage-to-current converter. The gain control signal is generated based on the detected sound pressure level, creating a feedback loop that automatically adjusts the converter's activation state to match the input conditions and minimize noise influence.
Data Source
AI summary
The present disclosure relates to a microphone driving device and a digital microphone including the same. A microphone driving device according to an embodiment of the inventive concept includes a voltage-to-current converter, a current-to-voltage converter, an analog-to-digital converter, a digital amplification unit, and a gain controller. The voltage-to-current converter converts an acoustic signal to an output current signal based on a gain control signal. The current-to-voltage converter converts the output current signal to an amplified voltage signal. The analog-to-digital converter converts the amplified voltage signal to a digital signal. The digital amplification unit amplifies the digital signal to an amplified digital signal based on the gain control signal. The gain controller generates a gain control signal. The microphone driving device and the digital microphone including the same according to the inventive concept may have a wide dynamic range and reduce the influence of noise.