调频/调幅/辅助信道(FM/AM/SCA)收音电路

<正> 一、SCA广播和接收的基本原理 SCA辅助信道广播是利用原有调频广播发射电波的载频,在原调制的立体声复合信号中再加入一个以67kHz为第二载频,最大频偏为±4kHz的调频信号(即第二副信道信号),组成一个新的复合信号(其频谱见图1),再以此复合信号对载频进行频率调制(第二副信道对主载频的调制度为10％)后发射出去。这样便可在不增加发射功率的情况下,既传送原有的立体声节目,又从辅助信道传送其它信息。辅助信道技术参数见表1。     

调频数据广播的原理及应用中需注意的问题

1 我国调频多工广播概况 调频多工广播是指在进行调频广播的同时,利用调频基带的空余频谱,通过调频副信道来传输声音、数据等各种业务信息,具有投资省、信息受众广泛、节约频谱等特点。 1992年我国第一个SCA电台——羊城交通台开播后,许多大中城市的调频电台相继开设了SCA广播,开办儿童专用节目或交通、气象、经济等服务性节目。遵循的标准是GB 4311.3—1984《调频广播立体声带附加信道》,它是在进行立体声广播的同时,增加一路在67kHz副载波上进行频率调制的     

副载波技术在应急广播系统的应用

从调频调制原理入手,分析RDS、SCA副载波技术的原理、在调频立体声广播中的应用条件,并提供副载波技术在应急广播系统中对广播终端的远程控制应用和提供图文信息发布应用的案例介绍。副载波技术应用于应急广播领域,具有开发周期短、技术风险低、设备成本低的优点。     

调频立体声发射机频偏与导频信号的关系

结合实例，分析探讨了在调频立体声广播过程中，调频立体声广播发射机调制深度与导频信号的关系。     

SCA广播

1958年,美国联邦通信委员会(FCC)批准调频广播电台开始开办用户付费收听的调频附加信道(SCA)广播。SCA是利用现有的调频立体声广播基带信号中空余的频谱部分,用来传送模拟信号的技术,最初是在67kHz调频副载波信道上插入频率调制的模拟声音,主要用于语言及音乐广播。图1为调频广播发送系统框图。在图中:1.立体声调制器的左、右通道音频输入端都采用一节15kHz低通滤波器,以保证立体声调制器     

谈谈调频立体声广播接收机

一、概述调频立体声广播开始于四十年代初期。当时采用两个独立的发射系统,接收机则同时接收两个不同频率的载波信号。由于所使用的设备结构复杂、成本高,效果也不好,因而这种调频立体声广播没有得到发展。直到1961年,采用一个载波发送两路立体声信号的广播制式才得到广泛的应用。调频立体声广播接收机与彩色电视机一样,也存在兼容性问题。为了使调频立体声广播接收机与普通(单声道)调频广播接收机一样既能收听立体声广播,又能收听普通调频广播节目,目前大多数国家都采用和差制。这种制式按载波调制方式来分,有调幅一调     

立体声调频广播发射机的测试系统

天津广播电视塔自20世纪90年代初建立调频广播发射台,至今已有7套调频节目。经过长期的发展,调频立体声广播以其保真度高,信噪比好,以及抗干扰性强等优势,深受广大听众喜爱。然而要确保调频立体声发射机具有良好的性能指标,才能有优良的收听效果。因此对调频立体声广播发射机的监测工作是保证广播质量的重要环节。文中主要介绍天津广播电视塔立体声调频广播发射机的测试系统及测量方法。1测试仪器天津广播电视塔调频立体声发射机指标测试使用的3台仪器为英国Marconi公司的2305调制分析仪,美国Sound-Technology公司的1710A综合分析仪及德国…     

调频数据广播原理及在应用中须注意的问题

1 我国调频多工广播概况 调频多工广播是指在进行调频广播的同时,利用调频基带的空余频谱,通过调频副信道来传输声音、数据等各种业务信息,具有投资省、信息受众广泛、节约频谱等特点。 1992年我国第一个SCA电台——羊城交通台开播后,许多大中城市的调频电台相继开设了SCA广播,开办儿童专用节目或交通、气象、经济等服务性节目。遵循的标准是GB 4311.3-1984《调频广播立体声带附加信道》,它是在进行立体声广播的同时,增加     

副载波技术在应急广播系统的应用

副载波技术具有开发周期短、成本低的优点,应用这项技术的风险比较低,可以更加及时的对信息进行发布,传达政令,从而达到紧急救灾的目的。本文对副载波技术的调频调制原理进行了介绍,对这项技术在调频立体声广播中的应用条件进行了分析,并对副载波技术在应急广播系统中的应用情况进行了介绍,希望对相关工作人员提供了一定帮助,实现对广播终端的远程控制,并保证图文信息的实时发布。     

数据广播系统

RDS是为了在广播中传输附加信息而设计的。本文介绍了调频立体声广播实现RDS的技术、发展和标准化,闸述了其信号的产生、接收、可传输信息及其编解码。     

Transmission scheme of high-capacity FM multiplex broadcastingsystem

FM multiplex broadcasting is a system for providing additional text and graphics, while maintaining compatibility with existing stereo sound broadcasting. The digital signals are multiplexed in a higher frequency band than baseband FM stereo signals. This paper describes a modulation method and an error correction method for a new high-capacity FM multiplex broadcasting system called DARC (Data Radio Channel), which has a bit rate of 16 kbit/s. Simulation results show that stereo sound signals interfere with a multiplexing signal under multipath conditions. LMSK (level controlled MSK) is proposed as a modulation scheme to ensure good transmission quality. It is shown that an error correction scheme using a product code of (272190) codes has a good performance for mobile reception. Field tests on the DARC for mobile reception are conducted in the service area of the NHK Tokyo FM station. These show that the correct reception rate can be obtained at more than 80% when transmitting information of 6 kbytes     

On Some Thedretical Considerations for RF Transmission of Quadraphonic Sound

Present proposed FM quadraphonic transmission systems are shown to be narrow-band FM schemes. Hence, the FM noise improvement properties of mono-FM transmission are not realizable. On theoretical grounds, it is shown that 1) there exists a compatible quadraphonic scheme that preserves the wide-band FM properties of stereophonic FM, 2) allows two additional channels of information to be impressed upon the carrier, and 3) offers a 4.7 db improvement in quadraphonic transmission as compared to the presently pro-proposed FM quadraphonic schemes.     

车载MP3的系统设计

基于微控制器系统的软硬件设计与调试,以及系统集成调试成功的基础上,完成了车载MP3的系统设计。利用技术成熟的单片机技术,以微处理器P89LPC935做主要控制器件,并通过扩展外围电路完成对整个系统的控制。车载MP3的系统设计具有播放USB海量存储设备上的MP3音频文件及FM立体声收音功能。     

无线电数据系统

欧广联(EBU)的无线电数据系统(RDS),是为在FM立体声广播中兼容传输附加信息而设计的。本文介绍了RDS的研究、发展与应用概况,阐述了RDS信号的产生、可传输的信息及其编码方法、数据格式和RDS接收机。     

An OFDM all digital in-band-on-channel (IBOC) AM and FM radiosolution using the PAC encoder

The advances in digital communications and compression algorithms have made more efficient and more robust transmission schemes possible. Radio broadcast systems have not fully utilized these advances to their benefit. All digital robust radio broadcast systems for the AM and the FM band are proposed. The proposed systems are based on orthogonal frequency division multiplexing (OFDM) technology in conjunction with PAC for both the AM and the FM bands. The Perceptual Audio Coder (PAC) developed by Bell Laboratories compresses audio signals very efficiently with CD-like quality at 96 kbps and stereo FM-like quality at 48 kbps. These are rates achievable with 200 kHz and 30 kHz bandwidths available per FM and AM station respectively. No new spectrum is required since the digital signals are transmitted within the current allocated FCC masks. In an FM channel, a wide-band data subchannel can be provided in addition to the 96 kbps error protected PAC audio information     

Performance of a digital stereo FM modulator with reduced outputresolution

A digital stereo FM modulator has been built using a direct digital synthesiser (DDS). The system incorporates a digital stereo generator to provide the modulating signal. The stereo generator was sampled at 228 kHz and interpolation by 2 was carried out to move the unwanted FM sidebands further away from the FM carrier, in order to facilitate filtering. The paper presents the effects of quantisation noise on the system output by reduction in output resolution. Demodulation has been carried out so that the signal to noise and distortion ratios (SINAD) could be measured for all spectral components ⩽53 kHz with different monotone modulation frequencies and varying output resolution. An FM simulation of this process has been developed and the FM spectra produced by it are shown to match the experimental spectra almost exactly. These spectra complied with broadcast standards even with as little as a 6 bit output. The experimental system, with a 10 bit output, gives a SINAD performance which is ⩾77 dB     

副载波对广播信号的频谱和模糊函数的影响

根据调频立体声广播中副载波的产生原理,针对广播信号的频谱和模糊函数图进行分析,指出:有副载波的广播信号的模糊函数图的零距离切面在导频信号的二分频的整数倍上出现相关峰、多普勒切面则由无副载波的广播信号的模糊函数图的多个多普勒切面加权相加而成;同时带宽较窄的有副载波的广播信号的模糊函数图的相关峰呈现多峰.最后给出了消除多峰的方法和实录信号的处理结果.     

一种低带内相位噪声的立体声FM合成器

研制一种低带内相位噪声的立体声FM频率合成器,该合成器基于小数分频锁相环技术,利用闭环方式对载波信号进行调制,显著提高系统的THD。采用CSMC0.5μm DPTM CMOS工艺对其设计,系统测试结果表明,立体声解调后SNR>70dB,THD<0.08,立体声分离度>40dB,最大带外辐射能量低于-90dBc/Hz。以上这些特性完全符合立体声发射机的要求。     

A theoretical and experimental study of noise and distortion in thereception of FM signals

A mathematical model is developed that can be used to analyze the effects of multipath on any modulation of an FM carrier. The predictions of this model are verified by simulation and by actual field testing. The model is used to analyze the existing FM stereo system and the proposed FMX system. The analysis, confirmed by field tests in over 15 000 locations, shows that FMX transmission significantly degrades reception on existing FM stereo receivers and that FMX receivers are inferior to FM stereo receivers for receiving FMX transmissions     

双极工艺用于立体声解调的线性锁相环的设计

设计了一种1.5μm双极工艺用于FM广播立体声解调的锁相环。锁相环中鉴相器由传统的吉尔伯特单元电路转变成上下对称的双开关电路,这样增加了鉴相灵敏度和鉴相范围。环路中增加了直流放大器单元,可很方便地通过调整其增益,来调整环路的阻尼系数,使环路在稳定性,锁定时间,噪声带宽方面做了很好的折中。从电路上实现了晶体压控振荡器的设计。锁相环路中的压控振荡器采用Q值很高的晶体做谐振网络,这样既可以保证窄带锁相环所具有的很高的Q值,也可以降低压控振荡器的相位噪声。