Parametric Audio Hybrid Modulation for Narrowband Ultrasonic Signals
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Solution Overview
Problem
Traditional modulation methods in parametric audio systems, such as DSB, result in wideband signals requiring broadband transducers and amplifiers, and lack control over bandwidth, leading to inefficiencies and distortion in signal reproduction.
Innovation Solution
A hybrid modulation method that combines amplitude and phase modulation, using a carrier signal modulated by an envelope signal with a predetermined function, allowing for control over the spectrum and reducing bandwidth through the Hilbert transform, enabling efficient signal reproduction with minimal distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If DSB modulation is used in parametric audio systems, then low distortion signal reproduction is achieved, but the bandwidth of the ultrasonic signal becomes very wide requiring broadband transducers and amplifiers
Solution Approach 1:
The patent changes the modulation parameter from simple amplitude modulation (DSB) to a hybrid approach combining amplitude modulation with phase modulation using a predetermined function. This parameter change allows the signal to maintain low distortion while concentrating spectral energy, thereby reducing the required bandwidth of the ultrasonic signal without sacrificing reproduction accuracy.
Solution Approach 2:
The patent introduces dynamic phase modulation based on a predetermined function that adapts to the audio signal characteristics. This dynamic adjustment of the modulated signal's phase component enables bandwidth reduction while preserving the low-distortion reproduction quality, making the system adaptable to different signal conditions.
2Manufacturing precision
If broadband transducers and amplifiers are used to reproduce the wideband modulated signal, then low distortion is achieved, but the device complexity and cost increase
Solution Approach 1:
By changing the modulation parameters to include phase modulation with a predetermined function, the patent reduces the spectral bandwidth of the modulated signal. This allows the use of narrower-band transducers and amplifiers, thereby reducing device complexity and cost while maintaining the low distortion performance through the hybrid modulation approach.
3Device complexity
If the bandwidth of the modulated signal is reduced, then transducer and amplifier requirements are relaxed, but control over the resulting bandwidth becomes limited
Solution Approach 1:
The patent employs dynamic phase modulation using a predetermined function that can be adjusted based on the audio signal characteristics. This dynamic approach provides flexible control over the modulated signal's bandwidth, allowing the system to adapt to different requirements while maintaining reduced transducer bandwidth requirements compared to traditional DSB modulation.
Solution Approach 2:
By introducing phase modulation as an additional parameter alongside amplitude modulation, the patent gains enhanced control flexibility over the modulated signal's spectral characteristics. This allows independent adjustment of bandwidth while maintaining the benefits of reduced transducer requirements.
Data Source
AI summary
A parametric audio system that permits greater control over the bandwidth of a modulated signal. The system includes a carrier signal generator for generating a carrier signal, at least one audio signal source for generating at least one audio signal, and a modulation component for generating an envelope signal based on the at least one audio signal, modulating the phase of the carrier signal based on a predetermined function to generate a first modulated signal, and multiplying the envelope signal and the first modulated signal to generate a second modulated signal. By selection of the predetermined function, the modulation component can alter the spectrum of the second modulated signal, thereby permitting greater control over the bandwidth of the second modulated signal.