DRM数字与模拟节目同播问题探讨

为了实现由模拟到数字的平滑过渡,解决频率与设备的短缺,同一部发射机可以按照不同的方案同时播出DRM数字节目与模拟节目。本文分析了几种可能的同播方式与相关问题,讨论了同播时电压和功率分配与接收质量的关系,指出了DX系列发射机同播运行的优势。     

Spectrally Efficient Digital Transmission Using Analog FM Radios

This paper explores the feasibility of using 4 level FM to enable digital transmission with a spectrum efficiency on the order of two bits per cycle of transmitted bandwidth when used with Frequency Modulated (FM) radios. A hybrid computer simulation was used to assess the compatibility of 4 level FM with the transfer characteristics of commercial FM radios and also to evaluate the performance of 4 level FM modulation under conditions of radio misalignment. It is shown that 4 level FM is able to provide good spectral efficiency without requiring modification or replacement of most current FM radios, It is also shown that 4 level FM performance is relatively insensitive to the transmission degradations typically encountered in fielded systems.     

Evaluation of a Method for Interference Control in Analog FM Systems

We discuss a possible method for interference control in radio systems whose desired signal is analog FM. The method utilizes the fact that the desired signal has a nearly constant envelope; with interference present, the composite envelope becomes noisy. A controlling processor measures this additional envelope noise, and iteratively adjusts the complex combining gain of an auxiliary signal to minimize the interference. The expected residual interference remaining after minimization is proportional to the reciprocal of the square of the rms envelope fluctuation of the desired signal. This result was confirmed in a laboratory simulation of an intersecting radio route case using both large and small index FM. Beginning with signal-to-interference ratios of 30 to 40 dB, the controller increased these numbers to about 60 dB, the expected theoretical limit for a signal with 0.1 percent rms envelope fluctuation.     

数字架构调频发射器为模拟挑战提供解决方案

数字影音播放能力已经从便携式媒体播放器和个人电脑发展到其它消费者电子设备，如：便携式导航装置（PND）和手机。数字影音文件的一个缺点就是：播放机构限于最初用于下载媒体的装置。例如，一个用户从他的移动服务供应商的终端购买了一首歌曲，他想在聚会或开车旅行时与朋友分享这首歌曲。其最好的方案就是：将音频通过无线方式发送给家里或汽车里现有的音频系统。     

数字电视模拟微波传输系统数字化改造方案

研究了数字电视微波传输技术,根据各项数字化改造指标,使改造后的微波传输系统达到设计要求,可将误码率控制在≤10-6,信号电平储备为＞20 dB,保证了电视广播传输在图像质量方面的稳定性。采用数字信号传输,有效的消除了原有模拟传输所带来的诸多问题,同时还保留了微波自身的优势,如抗击自然灾害能力强和易维护等特点。     

Spectral Analysis of Analog Video and Phase-Shift-Keying Data Transmitted by FM

Models of the video luminance and chrominance processes are presented and used to derive an expression of the FM power spectrum of colour TV signals. The proposed spectrum model accounts for the spectral components at the chroma subcarrier frequency and agrees closely with the measured spectrum.     

Partitioning Analog and Digital Processing in Mixed-Signal Systems

Shrinking feature sizes, combined with the need for low-power and lightweight components, fuel the desire to place large mixed-signal systems onto a single die. A major design issue in mixed-signal systems is the effect of digital switching noise coupled to sensitive analog circuits through the substrate. A method is presented for minimizing this effect by partitioning digital and analog processing into separate time blocks. The resulting trade-off between lost signal and increased energy consumption is explored. As an example, a GPS synchronizer design is analyzed with respect to modifications that can be made to increase performance, while minimizing any associated energy penalty. Application of the partitioning method to other communications systems is discussed.     

VLM Precoded SLM Technique for PAPR Reduction in OFDM Systems

Orthogonal frequency division multiplexing (OFDM) is perhaps the most spectrally efficient, robust transmission technique discovered so far for communication systems, and it also mitigates the problem of multipath environment. High peak-to-average power ratio (PAPR) has always been a major drawback of the OFDM systems. In this article, a new precoding technique has been proposed based on Vandermonde-like matrix (VLM) and selective mapping (SLM) to reduce PAPR in OFDM systems. VLM precoding reduces the autocorrelation of the input sequences while SLM takes an advantage of the fact that the PAPR is very sensitive to phase shifts of the signal. The main advantage of this proposed scheme is to achieve a significant reduction in PAPR without increasing the system complexity. Computer simulations show that, the proposed method outperforms the existing precoding techniques without degrading the error performance of the system.     

数据转换器:模拟与数字世界的桥梁

数字化需求的不断增长,对模拟技术——特别是数据转换器技术的需求变得更为重要。数字技术对信号转换技术的要求越来越高,本文介绍了数据转换器技术的发展和现状。     

模拟与数字音频系统连接中的电平设置

在数字视音频系统中仍有一些模拟设备在使用，连接时如音频电平设置不当，则会产生严重失真，降低系统的整体指标，该问题在实用中经常碰到，本文讲解了与音频电平设置有关的基本概念，分析了数字与模拟设备连接时产生失真的关键环节，提出了正确设置衔接电平的方法及国际上的依据。     

Direct Conversion of FM Magnetic Tape Data into Digital Form

A system is described for decoding frequency-modulated magnetic tape data directly into digital form suitable for input to a digital computer. Included in the system is a very precise method used to compensate for flutter errors. The bypassing of standard demodulation, filtering, and analog-to-digital conversion permits a significant improvement in signal-to-noise ratio. This type of system is most advantageous when reproducing data from magnetic decks whose signal-to-noise ratios cannot be reliably expected to remain at a satisfactory level. Using electrocardiograms, it has been demonstrated that a real gain in the detection of low-amplitude waveforms can be achieved with this system as compared to conventional reproducing.     

山东台地球站模拟数字系统实施一体化监控

山东电视台地球站在模拟向数字过渡时期,为了同时保证模拟和数字系统正常播出,对系统进行了技术改造,采用模拟和数字系统并播方式,通过对模拟和数字系统一体化监控的设计,值班人员借助于微机等手段,能够完成模拟和数字双星并发的监控要求,大大节省了人力物力,减轻了值班人员的工作压力,为安全播出提供了可靠的保证.     

Combined Analog and Digital Error-Correcting Codes for Analog Information Sources

This paper focuses on error-correcting codes for analog signals. Generally, error-correcting codes exhibit a threshold effect, which degrades performance at the low signal-to-noise ratio (SNR) range. We propose two error-correction alternatives based on chaotic dynamical systems, which improve threshold performance relative to previously proposed methods. The first one, which is based on principles of diversity, exhibits a very simple decoder. The second alternative, which is based on a low-density parity-check (LDPC) code, attains a significantly lower threshold. Theoretical analysis and simulations are provided.     

非线性系统的模拟电路与数字电路仿真实验平台的设计

对自动控制原理实验课程进行教学改革,设计了综合设计性实验———非线性系统分析与实验。采用Matlab对非线性系统进行了仿真,通过运算放大器设计了非线性模拟电路,并采用Multisim软件进行仿真,观测到了丰富的混沌行为。同时通过单片机处理器设计了数字电路,利用Proteus软件进行了仿真,结果与模拟电路基本一致,该实验从理论分析到模拟电路与数字电路软件仿真,从基本电路设计到具体实现,培养了学生的多学科的融合,工程能力程意识,激发了学生学习兴趣和创新精神。     

Digital Multiplexing of Analog Data in a Microprocessor Controlled Data Acquisition System

An analog data acquisition system typically consists of an analog multiplexer followed by an analog to digital (A/D) converter. An alternative configuration uses multiple comparators (one per input) followed by a digital multiplexer. If the control functions for A/D conversion are incorporated into a microprocessor, several potentially interesting data acquisition and conversion strategies are available. At first thought, an interrupt-driven conversion process which simultaneously searches all inputs in parallel for a level match appears attractive. However, analysis shows that a sequential conversion of the inputs, one at a time, using the successive approximation algorithm, is usually superior.     

Application of Coded Modulation to 1.544-Mbit/s Data-in-Voice Modems for FDM FM and SSB Analog Radio Systems

The technical issues relevant to providing high-quality digital service over analog radio using 1.544-Mbit/s DS-1 data-invoice modems operating through analog supergroup channels with 256-QAM modulation are reviewed. By means of a typical example, the desirability of increasing the fading margin when operating over FM radio systems is demonstrated. This motivates the consideration of coded modulation as a means of extending the threshold of the modem System, so that operation of the modem can be achieved in supergroup channels located higher in the radio baseband. It is found that trellis coded modulation provides better improvement of threshold performance than lattice coded modulation when the actual coding gain realized near the R0channel bound is used rather than the high signalto-noise-ratio (SNR)asymptotic coding gains. Using Ungerboeck's eight-state trellis code [3], a coding gain of approximately 2 dB is found for operation at 28 dB SNR (1 dB from the R0bound). Furthermore, it is found that even at this low operating SNR (where error events at the coded modulation receiver ouput can be long), high-rate, interleaved Reed-Solomon codes, used for burst noise protection at high SNR, still provide over 2 dB of additional coding gain.     

数字调频激励器

1引言近年来,山西省广播电视局先后购置5部10kW哈里斯全固态数字调频广播发射机,分别承担中央台、山西台多套调频广播节目的发射任务。经几年工作运行,机器性能稳定可靠,技术指标质量高,音质可与CD媲美,显示了数字化发射机的优越性。现对整个发射机的核心部分数字激励器的性能及原理作简要介绍。2数字激励器DIGITCD数字调频激励器是美国哈里斯公司上世纪末的最新产品。如果输入一个数字的或模拟的复合立体声信号,输出端就会得到一个调频功率电平达55W的载波信号,调频(FM)调制处理完全数字化。同时,它还具有捷变频率的功能,可用于发射…