Hybrid DPWM implementation using coarse and fine programmable ADLL

In the paper we propose a novel architecture and implementation of 11-bit Digital Pulse Width Modulator (DPWM) circuit based on previously known building blocks. Linearized Class-AD Double-sided (LADD) algorithm has been used to calculate the DPWM signals of the 11-bit resolution hybrid DPWM for a Class-AD digital audio amplifier. Noise-shaping process is used to support high fidelity with practical values of time resolution. The proposed DPWM circuit is composed of 8-bit counter and Analog Delay Locked Loop (ADLL) using 4-bit tapped delay line. A dual ADLL employing coarse and fine programmable delay element is used to adjust the delay time of delay line and lock it to required time. The coarse- as well as fine-delay lines are implemented as a cascade of variable-delay elements based on shunt capacitor delay element or single-ended Schmitt trigger. The proposed 11-bit DPWM circuit, at a switching frequency of 352.8 kHz and clock generator frequency of 90.3 MHz allows us to attain SNR of 120 dB and THD of the output signal less than 0.1% within the audio baseband and modulation index M=0.95. Basic verification of circuit manufacturability and simulation results (Monte Carlo analysis) for real CMOS process are presented.     

三网融合背景下的通信声学

通信声学是声学与信息技术相互渗透融合的产物,随着信号处理技术和电声学技术的发展,其研究和应用领域得到快速扩展.介绍了通信声学的3个主要方向:声接收技术,声传输技术和声发射技术的研究现状和热点.重点探讨了在三网融合背景下,通信声学的应用前景及所面临的挑战.     

基于国半LM3886的高保真合并式音频功率放大器

顺应当前节能减排的原则,开发了一款性价比极高、性能较完善的基干国半LM3886的高保真合并式音频功率放大器,该合并武音频功率放大器能匹配绝大多数书架音箱.实测指标与实际试听都达到较高水平.     

MPACodec移动音频编解码技术

利用波形编码和参数编码的优点,设计了一种移动音频编码技术.该技术采用子带滤波、预测编码、变换编码、频带扩展和参数立体声编码技术,以较低的复杂度实现了宽带音频信号的高效率编码.     

东北师范大学体育馆扩声系统介绍

东北师范大学体育馆扩声系统具备功能多、稳定性好等特点.设备配置为现场扩声,设备选型均依据国际上先进、经济上合理、使用上安全可靠、维护上便利快捷的原则,保证有良好的扩声效果.本系统采用QSCBASIS系列数字音频处理核心在完成了音频信号的处理和传输的同时,配合QSC可监控的功率放大器,实现功放网络远程监控的功能.在扬声器...     

视音频信息检索的需求、研究与实际应用

自动编目和信息检索的核心是索引,目前几乎所有的资料管理机构仍然主要依靠某种形式的分类体系对文献或各种类型的内容进行分类。随着计算机技术的广泛应用,自动索引提供了对索引问题的一种新的认识,即索引问题在某种程度上与系统更为相关,而不是与用户需求相关。区分这一点非常重要,即检索是以基于规则的计算为核心,还是以人的主观判断为核心。为此,在对信息检索的各种模型作了简介和性能比较之后,详细讨论了当前广电系统视音频信息检索的需求、特点、研究现状、实际应用和下一步的进展。     

基于FPGA的MADI接口设计

常用的音频传输接口I2S只能传输两路音频信号即左右通道,为了提高单根线路的传输能力,在单根传输线上传输多路音频数据,此设计完成了多通道音频接口的设计,使之能够发送和接收多通道的音频数据。32路的立体声转化成64个通道通过光纤或同轴电缆串行发送出去,与此同时可以接收到64个通道的串行音频数据,转化成32路的立体声。该设计主要采用Xilinx公司的FPGA芯片Spartan3e和接收发送芯片CY7C9689配合完成,由FPGA控制CY7C9689的接收与发送过程。     

A survey of efficient MDCT implementations in MP3 audio coding standard: Retrospective and state-of-the-art

This tutorial paper describes various efficient implementations (published and new unpublished) of the forward and backward modified discrete cosine transform (MDCT) in the MPEG layer III (MP3) audio coding standard developed in the time period 1990-2010, including the efficient implementation of polyphase filter banks for completeness. The efficient MDCT implementations are discussed in the context of (fast) complete analysis/synthesis MDCT filter banks in the MP3 encoder and decoder. In general, for each efficient forward/backward MDCT block transforms implementation are presented: complete formulas or sparse matrix factorizations of the algorithm, the corresponding signal flow graph for the short audio block and the total arithmetic complexity as well as the useful comments related to improving the arithmetic complexity and a possible structural simplification of the algorithm. Finally, all efficient forward/backward MDCT implementations are compared both in terms of the arithmetic complexity and structural simplicity. It is important to note that almost all presented algorithms can be also used for the 2ⁿ-length data blocks in others MPEG audio coding standards and proprietary audio compression algorithms.     

基于信息极大化的ICA算法研究

独立成分分析是在缺乏混合系统和源信号先验知识的条件下,仅通过观测信号来恢复出源信号,已经成为数字信号处理的重要研究方向。文中在研究独立成分分析理论的基础上,介绍了一种基于信息极大化的分离算法,并对混合音频信号进行仿真试验,成功分离出了混合信号中的各个独立成分,仿真结果验证了信息极大化分离算法在语音增强和助听器功能改善方面的优越性,具有一定的理论研究和应用价值。     

语音放大电路的设计与实现

设计了一款低成本、大功率的语音放大器。该设计采用带通滤波电路对输入的音频信号进行处理,专业音频放大芯片NE5532对语音信号进行初级功率放大、三极管和大功率晶体管2N7300组成后级功率放大后推动扬声器。通过测试,该语音放大电路可以提供40 W的功率,远大于普通家用语音功率放大器,而且成本又远低于专业语音功率放大器,完全满足需要。