Digital System Realization Of Broadband Phased Parametric Array

The problem of noise pollution is becoming more and more serious,and more and more people are beginning to understand and realize that this invisible killer is eroding our physical and mental health.Noise from people’s social activities and audio equipment,as well as the noise from transportation such as trains and planes,is highly related to people’s living conditions and subjective wishes,which can easily lead to health problems such as sleep disorders and stress.These noises are caused by the omnidirectivity of lowfrequency signals.The emergence of the parametric array can solve these problems.It can project the sound to a specific area according to the user’s own wishes,and the audio will be instantly attenuated outside the area.Just like a flashlight,it can send out a highconvergence "sound beam".Lightness,thinness and miniaturization are the advantages of the parametric array,but its directivity control is very difficult,and there are also disadvantages such as low electroacoustic conversion efficiency and high nonlinear distortion.In order to solve the above key problems,more precise directivity control of the parametric array is carried out,and the development of directional acoustic wave emission technology based on the parametric array is promoted.The beamforming algorithm of broadband phased parametric array is researched,and a broadband phased parametric array digital system is built.Focusing on the realization of the broadband phased parametric array digital system,the main work content is as follows:Analyze the early nonlinear acoustic theory to the later parametric array acoustic theory,Westervelt equation,and Berktay far-field model.On the basis of the conventional parametric array,a broadband phased parametric array digital system is proposed,and a fixed-point acoustic wave launch device based on the principle of the parametric array is designed to limit the audio sound wave to a smaller area,thereby achieving more precise "fixed-point " acoustic emission.In order to solve the technical problem of parametric array difference frequency low sound pressure level and insufficient scalability,it is proposed to modulate the modulated signal into a single-bit output,which realizes multi-channel phase-controlled beam control.With limited processor resources,the interface utilization rate of the system is improved.Not only saves resources,reduces the size of the device,but also makes the communication between the device and the device simple.In order to solve the input quantization noise in the digital system,and the quantization noise problem when quantizing the multi-bit signal into a single-bit signal.Using oversampling and noise shaping algorithms to suppress noise,the results show that the algorithm can improve the sound quality of directional audio,and quantization noise is suppressed.Combining the phased array and the parametric array,based on the uniform linear array model,a broadband phased parametric array beamforming algorithm is proposed,and the achievable effect is analyzed.The beamforming algorithm is applied to the broadband phased parametric array digital system,and the measurement results show that the algorithm can control the beam directivity.In order to improve the conversion efficiency of electro-acoustics and reduce the noise interference,the driving circuit is researched,and the corresponding impedance matching circuit and filter circuit are designed.