Analysis and improvement of a high performance digital speaker system

虽然大量的音乐数据是以数字信息的形式存储的，比如cd和md，但模拟驱动器仍然是扬声器的主要部件。如果扬声器可以以数字方式驱动，那么从输入到输出的所有过程都可以以数字方式进行。因此，模拟功率放大器和其他一些组件变得不必要，可以实现小，轻，高质量的扬声器。在这项研究中，我们提出了一种数位驱动的压电扬声器，采用多位delta-sigma调制。●估计压电扬声器频率响应：压电扬声器除200kHz以下的低频段外，频率响应平坦。在两个或两个以上的元素中，特征变化大于10%。畸变：由于压电器件具有非线性特性，器件会产生畸变，这是实现薄扬声器的一个问题。在谐波失真特性实验中，测得c…c…c的失真率比较高，达到32%（三次失真）。当压电器件由模拟电路驱动时，需要减小畸变影响的方法。一种高性能数字直驱扬声器噪声成形动态元素匹配方法的研究：改进了数字扬声器的噪声成形动态元素匹配方法，通过仿真验证了该方法的性能。设计了逻辑电路，并利用FPGA器件实现了逻辑电路。通过对该FPGA的评估，所提出的nsdm电路的规模比传统的小20%。采用FPGA和高速驱动电路对所提出的扬声器系统的整体特性进行评估：对输入正弦波的特性进行评估。因此，当副扬声器已经布置到平面板上时，副扬声器的变化和布置使副扬声器本身的特性引起变化。nsdm的作用减小了这种影响，并得到了实验的证实。实现了2%或更小的失真。少

Although a substantial quantity of music data is stored as digital information, as in the case of CDs and MDs, an analog drive is still the main component of a loudspeaker. If the speaker can be driven digitally, it becomes possible to perform all processes from the input to the output digitally. As a result, the analog power amplifier and some other components become unnecessary and a small, light, and high-quality speaker can be achieved. In this research, we propose a digital-driven piezoelectric speaker employing multi-bit delta-sigma modulation.●Estimation of a piezoelectric speakerFrequency response : A piezoelectric speaker shows flat frequency response except low frequency band under 200kHz. Among two or more elements, the characteristics variation over 10% is observed.Distortion: Since a piezoelectric device has nonlinear characteristics, the device generates distortion which is an issue to realize a thin speaker. In the experiment of harmonic-distortion characteristics, the c … More omparatively high distortion rate of 32% (3rd distortion) is measured. When piezoelectric device is driven by an analog circuit, the method to reduce the influence of distortion is required.●A high performance digital direct drive loudspeakerStudy of a noise shaping dynamic element matching method (NSDEM) : Improving NSDEM for the digital speaker, the performance was confirmed by simulations. The logical circuit was designed, and the logic circuits were implemented by using a FPGA device. From evaluation of this FPGA, the scale of the circuit of proposed NSDEM is 20% smaller than conventional one.●Overall evaluation of the proposed digital direct drive loudspeakerEvaluation of the overall characteristic of the proposed speaker system using a FPGA and high speed driver circuit : The characteristics inputting a sinusoidal wave were evaluated. As a result, when the sub-loudspeaker has been arranged to the plane board, the variation of the sub-loudspeaker and arrangement make the characteristics of the sub-loudspeaker itself cause variation. The influence was reduced by the effect of NSDEM and it was confirmed by experiment. The distortion of 2% or less was realized. Less