Single-Transducer Driver Circuit for Audio-Ultrasonic Distortion Control
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Solution Overview
Problem
When using the same transducer to generate both audio and ultrasonic signals, audible distortion occurs due to intermodulation products caused by non-linearities, which are particularly objectionable and noticeable, especially with swept frequency ultrasonic signals or periodic bursts.
Innovation Solution
The driver circuitry dynamically adjusts the ultrasonic signal's amplitude, pulse duration, duty cycle, repetition frequency, or bandwidth 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
1Ease of manufacture
If the same transducer is used to generate both audio and ultrasonic signals, 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 is dynamically adjusted based on the audio signal level - when audio signal level increases, ultrasonic amplitude decreases and pulse duration increases, and vice versa. This dynamic adaptation prevents intermodulation distortion while maintaining both audio and ultrasonic functionality from the same transducer.
Solution Approach 2:
The patent changes the parameters of the ultrasonic signal (amplitude, pulse duration, duty cycle, repetition frequency, frequency span) based on the audio signal level. By varying these parameters dynamically, the system prevents non-linear interactions that cause audible distortion while maintaining cost-effectiveness of using a single transducer for both functions.
2Measurement precision
If ultrasonic signal amplitude is increased to improve ultrasonic detection capability, then detection sensitivity is improved, but intermodulation distortion becomes more noticeable
Solution Approach 1:
The system dynamically adjusts ultrasonic signal parameters based on audio signal level. When audio signal level is low, ultrasonic amplitude can be increased for better detection sensitivity. When audio signal level is high, ultrasonic amplitude is reduced to prevent distortion. This dynamic balancing allows optimal detection sensitivity without causing noticeable distortion.
Solution Approach 2:
The system uses feedback by monitoring the audio signal level and using this information to adjust the ultrasonic signal parameters. The audio signal level serves as feedback that controls the ultrasonic amplitude, pulse duration, and other parameters, ensuring that ultrasonic detection sensitivity is optimized without creating intermodulation distortion.
3Power
If audio signal level is increased for louder playback, then audio output quality is improved, but ultrasonic signal quality deteriorates due to reduced amplitude
Solution Approach 1:
The system dynamically compensates for ultrasonic signal quality by adjusting pulse duration and duty cycle when audio signal level is high. Even though ultrasonic amplitude must be reduced when audio playback is loud, the increased pulse duration and duty cycle maintain the effective energy and detection capability of the ultrasonic signal, preserving signal quality.
Solution Approach 2:
The system uses periodic ultrasonic signal bursts with variable duty cycle. When audio signal level is high, the duty cycle is increased to provide more ultrasonic energy over time, compensating for the reduced amplitude and maintaining ultrasonic signal quality despite louder audio playback.
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 concurrent ultrasonic and audio signal transmission without compromising signal-to-noise ratio, enabling louder music playback and maintaining the functionality of ultrasonic applications.
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.