英国Allen ＆ Heath PA系列之新型有源机型——PA-12

继推出PA20和PA28现场立体声调音台之后,英国Allen&Heath公司又进而推出了该系列的一款既可安装在机架上、又可单独放置的新产品——PA12混音器。 该混音器的主要特点是:配有新型元衰减前置放大器、内置可编辑型数字效果器、SPDIF格式数字音频信号输出和参数式模拟音频信号输出均衡器。     

一款数字功率放大器的设计

设计了一款基于DDX功率驱动技术、既具有USB数字音频接口又具有模拟音频接口的数字音频功率放大器UPA001。DDX技术的引入使UPA001具有极高的效率和极低的失真。数字音频接口和数字处理技术的引入,使音频信号的传输和处理过程不会产生附加的失真和噪声。模拟音频接口和模拟处理技术的引入,使具有模拟音频输出接口的设备可以直接使用UPA001。     

数字音频基础理论的分析

在数字音频的处理中,理论指导处于很重要的地位。要想制作出品质优良的数字音频作品,就要认真学习和使用好效果器。对于常用的音频术语和效果器进行分析,如均衡器、压限器、激励器、失真、混响等,特别是一些主要技术参数。     

MIPRO更名公告

美国Symetrix(思美)公司是一家专业音频处理器生产厂商，其产品从最初专为演播室设计的音频处理器，一直发展到现在能应用在各种场所的网络数字音频处理器。     

数字音频工作站电平的校准

随着数字音频广播技术的发展,以数字音频工作站为中心的数字化采编播系统的应用越来越广泛,音频工作站电平的确定和校准对优质安全播出有着极其重要的作用。中国目前的广播系统中,大多数是模拟系统和数字音频工作站混合使用。下面就谈谈数字音频工作站与传统模拟设备在安装过程中的电平调整问题。数字音频工作站中的声卡数字音频工作站作为软硬件一体的专业音频设备,其输入输出指标主要是声卡的指标。目前,中国广播电台的音频工作站中使用的大多数是法国Digigram公司生产的广播用Pcx9,Pcx11,Pcx2系列声卡,采用平衡输入输出,22?dBu高阻输入…     

基于网络技术的演播室群实时数字音频系统的设计与应用(1)

以使用于电视制播的演播室群实时音频系统为基点,分析对比了目前业界普遍使用的"以数字调音台为核心、以模拟调音台为备份的模数音频混合系统"的优劣,阐述了基于网络技术的演播室群实时数字音频系统的设计和构建要点以及系统创新点,具有一定的应用和推广价值。     

数字音频工作站及数字音频压缩技术

数字音频工作站就是把模拟音频信号数字化或直接把数字音频信号记录在一定的媒体上，具有记录、重放、均衡、延时、时间压扩、多轨合成、降噪处理、剪辑等多种处理功能的设备。该设备具有动态范围大、无科晃、多次复录质量不变、易实现录播自动化及音频数据共享、音频处理功能用软件实现等特点，所以它的使用越来越广泛。由于数字音频工作站的使用，对数字化音频信号的存贮和传输提出了更高的要求，由此引出了数字音频的数据压缩编码技术。本文就以上两方面内容进行探讨。     

新型数字矩阵处理器SC64

数字矩阵处理器SC64拥有64个通道的模拟输入／输出,从SC64处理器的面板显示可以清楚地看到那个通道是模拟音频信号输入或是模拟音频信号输出,也还可以查看到该通道是数字音频信号输入或数字音频信号输出,详见下图1。这种64通道的输入／输出安排成8个组（A、B、C、D、E、F、G、H组）,每组有8个输入／输出接口槽,通过这些接口槽容易构建出种种不同的负载结构,模拟输入接口槽能接纳带有Mic／Line开关选择和可提供需要幻像电源的宽带音频信号源。另外,本机还设有两个高速传输选择接口槽,用于将来的高速宽带音频信号的输入／输出传输。所有这些结构都安装在标准2U型的机架内。     

对数字音频技术的思考

数字技术对人类的发展产生了巨大的影响,它以惊人的速度,渗透到社会与生活的方方面面。现在数字技术已全面进入到广播影视领域,给我们的行业带来巨大的变革。清楚地把握数字音频技术的发展动向,对正确推进广播影视音频的数字化进程将有极其重要的意义。要把握数字音频技术发展的方向,首先需对数字音频与模拟音频技术有科学的认识,并清楚这样一个概念,数字化是一种手段,但我们始终离不开这个模拟的世界,我们要分清音频技术模拟与数字音频技术各自的优势和弱点。在音频的质量上来说,数字音频通过模数/数模转换后,越接近模拟音质就越好。但是,…     

浅谈数字音频工作站在广播电台中的应用及维护

随着广播设备技术的不断发展,数字音频工作站在广播电台中得到了广泛的应用.数字音频工作站通过强大的音频信号处理,实现对广播电台各种音频节目的录制、播放、管理等,提高了音频节目的制作质量和管理效率.基于此,本文从数字音频工作站的基本功能出发,对数字音频工作站的应用进行系统的分析,并就数字音频工作站的维护问题进行介绍.     

A novel design methodology for low pass filter stage of a voltage source inverter

A low pass filter, an invariable constituent of a PWM based voltage source inverter, poses several challenges in its design. With a higher rating of the inverter, the volume as well as the cost of the components increases. With time, the filter design has evolved from the simpler first order filter to higher orders, the most popular being the third order LCL filters. Though the attenuation of high frequency components, offered by the higher order filters, has resulted in improved efficiency, the inherent instability of the higher order filter systems requires complex controls for proper functioning. Keeping this in mind, the paper describes the design methodology of a second order LC filter system based on certain performance indices that reflect the ratings of the components.     

超声切削加工的声系统阻抗匹配问题研究

匹配电路作为超声发生器的电系统与声系统的传输纽带,其设计的好坏决定了整个超声加工系统的工作性能。基于实验,分析了匹配电路元件的不同连接方式对声系统性能的影响;提出了基于最小功率点与能量传输效率综合最优的匹配方式与原则,并验证了此种匹配方式能大幅提升切削加工的稳定性。为同类超声加工工艺的匹配电路参数的选取和声系统性能优化提供了依据。     

相位均衡器技术在水声接收机的应用

滤波器相位的非线性引起的信号失真是超短基线接收机系统中必须要解决的问题之一。采用常规滤波器与全通网络级联的方法设计了一种相位均衡器,解决了仅使用常规滤波器带来的非线性相位问题,使超短基线接收机在带宽内保持线性相位。给出了全通网络的原理、电路结构推导,分析了该网络中各参量对相位的影响。在设计实例中,相位均衡技术应用到实际硬件电路中进行测试,并结合试验数据及仿真结果对系统的性能进行评估。测试结果证明了相位均衡器可以实现相位的均衡校正功能,在水声接收机领域中有良好的应用前景。     

Nonlinear equalization for holographic data storage systems

Despite the fact that the channel in a holographic data-storage system is nonlinear, most of the existing approaches use linear equalization for data recovery. We present a novel and simple to implement nonlinear equalization approach based on a minimum mean-square-error criterion. We use a quadratic equalizer whose complexity is comparable to that of a linear equalizer. We also explore the effectiveness of a nonlinear equalization target as compared with the conventional linear target. Bit-error-rate (BER) performance is studied for channels having electronics noise, optical noise, and a different span of intersymbol interference. With a linear target, whereas the linear equalizer exhibits an error floor in the BER performance, the quadratic equalizer significantly improves the performance with no sign of error floor even up to 10(-7). With a nonlinear target, whereas the quadratic equalizer provides an additional performance gain of 1-2 dB, the error-floor problem of the linear equalizer has been considerably alleviated, thereby significantly improving the latter's performance. A theoretical performance analysis of the nonlinear receiver with non-Gaussian noise is also presented. A simplified approach is developed to compute the underlying probability density functions, optimum detector threshold, and BER using the theoretical analysis. Numerical results show that the theoretical predictions agree well with simulations.     

机器人一体化关节驱动系统

为提高机器人的运动性能,其各个关节的驱动系统性能的提高成为关键。随着控制理论的提高和伺服技术的进步,永磁同步电机的伺服性能得到极大提高,在工业自动化中应用广泛。由交流伺服系统直接驱动的机器人关节一体化设计已成为一个重要研究方向。本文详述了高性能的机器人一体化关节驱动系统的设计和开发。     

A study of PRML systems by write and read equalization

A new partial response (PR) channel which contains the write equalizer in addition to conventional PR channel is proposed. Our write equalizer outputs DC-free waveforms of two levels. Our read equalizer can reduce high-frequency noise, and what is more, it has little degradation of eye opening. The PR channels in combination with Viterbi decoder give partial response maximum-likelihood (PRML) systems which exhibit a good performance. The bit error rates for several PRML systems are obtained by computer simulation, where a Lorentzian channel with additive white Gaussian noise is assumed. The results shows that PR(1,1,-1,-1) system has an excellent performance in high density recording for a system in which the small transition spacings required by our write equalization is allowed     

Single network adaptive critic design for power system stabilisers

The recently developed single network adaptive critic (SNAC) design has been used in this study to design a power system stabiliser (PSS) for enhancing the small-signal stability of power systems over a wide range of operating conditions. PSS design is formulated as a discrete non-linear quadratic regulator problem. SNAC is then used to solve the resulting discrete-time optimal control problem. SNAC uses only a single critic neural network instead of the action-critic dual network architecture of typical adaptive critic designs. SNAC eliminates the iterative training loops between the action and critic networks and greatly simplifies the training procedure. The performance of the proposed PSS has been tested on a single machine infinite bus test system for various system and loading conditions. The proposed stabiliser, which is relatively easier to synthesise, consistently outperformed stabilisers based on conventional lead-lag and linear quadratic regulator designs.     

输电塔结构离散变量优化设计方法

鉴于格构式输电塔结构具有杆件众多、型式复杂等显著特点,所以建设和发展既安全可靠,又经济合理的此类结构一直是工程界的研究热点和难点。因此,该文提出了一套完整的基于蚁群优化算法的输电塔结构离散变量优化设计方法。该方法是在结构的截面、拓扑和形状变量统一转化为离散变量的基础上,将4类不同层次的优化问题统一为不同规模的标准化旅行商问题,并最终采用蚁群算法实现输电塔结构的优化设计。通过对某一实际输电塔结构的优化设计表明:该文方法不仅可以简单高效的求解输电塔结构的截面、拓扑、形状和布局优化问题,而且清晰明确的阐述了不同优化内容的物理意义和优化准则,实现了优化方法和思路的统一。此外,基于蚁群算法的输电塔结构离散变量优化方法通用性强、易于程序化,而且具有非常好的工程应用前景。     

Using self‐constructing recurrent fuzzy neural network as a digital channel equalizer

Abstract

In this paper the design of a self‐constructing recurrent fuzzy neural network (SCRFNN)‐based digital channel equalizer is proposed. It is found that a digital channel equalizer based on SCRFNN can recover channel distortions effectively. We compare the performance of SCRFNN with adaptive‐based‐network fuzzy inference system (ANFIS) and the Bayesian equalizers in complex‐valued linear channels. Our simulations show that the performance of SCRFNN is close to the Bayesian optimal solution. Furthermore, the hardware requirement of the trained SCRFNN equalizer is relatively lower than the other two structures.     

混合离散变量模拟退火方法及其应用

基于海洋工程中存在的设计变量为离散型和连续型的混合离散变量的情况,探讨了一种优化设计问题的方法———混合离散模拟退火法.该方法相对常规模拟退火方法有一定改进并且针对混合离散变量进行了特定处理.实际算例计算表明,该方法可用于海洋工程优化设计中,其结果不需圆整,而且其解题可靠性和效率相当高.