Shared Transducer Driver Circuit for Audio-Ultrasonic Distortion Control
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Solution Overview
Problem
Existing devices that use the same transducer for both audio and ultrasonic signals often experience audible distortion due to intermodulation products caused by non-linearities, which are particularly objectionable and noticeable when the ultrasonic signal is modulated or in the form of periodic bursts.
Innovation Solution
The implementation of driver circuitry that adjusts the ultrasonic signal's amplitude, pulse duration, duty cycle, repetition frequency, or frequency span based on the level of the audio signal component, using operational variables such as audio input levels or transducer parameters to minimize audible distortion by modifying the ultrasonic signal in response to audio signal conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If audio and ultrasonic signals are driven from the same transducer, then material cost and assembly cost are saved and device dimensions are reduced, but audible distortion occurs due to intermodulation products
Solution Approach 1:
The patent applies dynamics by making the ultrasonic signal parameters (amplitude, pulse duration, duty cycle, repetition frequency, or frequency span) variable rather than fixed. The ultrasonic signal generation module dynamically adjusts these parameters based on the audio signal level to minimize intermodulation distortion while maintaining cost savings from using a single transducer.
Solution Approach 2:
The patent implements parameter changes by modifying the ultrasonic signal characteristics (amplitude, pulse duration, duty cycle, repetition frequency, or frequency span) in response to audio signal conditions. This allows the system to maintain the benefit of a single transducer while reducing audible distortion through adaptive parameter adjustment.
2Measurement precision
If the ultrasonic signal amplitude is increased to improve signal quality, then detection capability is enhanced, but intermodulation artifacts increase
Solution Approach 1:
The system dynamically adjusts the ultrasonic signal amplitude based on the audio signal level. When audio signal levels are high, the ultrasonic amplitude is reduced to minimize intermodulation artifacts. When audio levels are low, the ultrasonic amplitude can be increased to maintain detection capability, thus resolving the contradiction adaptively.
Solution Approach 2:
The patent applies preliminary anti-action by proactively reducing the ultrasonic signal amplitude before intermodulation distortion becomes problematic. The ultrasonic signal generation module monitors audio signal levels and preemptively adjusts ultrasonic parameters to prevent excessive intermodulation artifacts from occurring.
3Power
If the audio signal level is increased to provide louder playback, then audio output is improved, but the ultrasonic signal quality deteriorates
Solution Approach 1:
The system dynamically balances audio and ultrasonic signal levels by adjusting ultrasonic parameters in response to audio signal conditions. This allows the system to provide loud audio playback when needed while maintaining adequate ultrasonic signal quality by adaptively modifying ultrasonic amplitude, pulse duration, duty cycle, repetition frequency, or frequency span.
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 significantly reduces audible distortion and allows for louder music playback while maintaining signal quality, ensuring that the combined audio and ultrasonic signals remain within safe amplitude limits to avoid clipping and intermodulation artifacts.
Implementation Method 1
driver circuitry for driving an electroacoustic transducer to provide an output comprising both ultrasonic and audio signal components
Data Source
AI summary
Driver circuitry is disclosed for driving an electroacoustic transducer to provide an output comprising both ultrasonic and audio signal components. The driver circuitry comprises an adjustment module configured to reduce the level of said ultrasonic component signal in response to an increase in an operational variable indicative of a level of said audio signal component, while also increasing the pulse duration, duty cycle, repetition frequency or frequency span or bandwidth of the ultrasonic component.