CDR调频数字音频广播信源编码技术

本文介绍了一种适用于我国调频数字音频广播的音频信源编码技术,具有较高的编码效率及分层编码结构,允许在一个模拟调频频道内传输多套数字立体声节目或一路环绕声节目,并保持较好的主观声音质量,同时可匹配信道分层特点,能够提供立体声和环绕声两种分层编码模式,从而兼顾了数字调频广播的服务范围和服务质量。     

迎接数字广播新世纪——浅析DAB数码广播的现状与发展

民用广播和收音机产生于20世纪初，前后经历了调幅（AM）、调频（FM）、调频立体声（FMSTEREO）和数字音频（DAB）三代广播，所使用的频率被划分为长波（LW）、中波（MW）、短波（SW）、超短波调频（FM）和卫星调频，广播接收机先后出现了矿石收音机、电子管收音机、晶体管收音机、集成电路收音机和数字接收机，体积不断变小的同时，功能却不断增强，从而使收听效果变得越来越好。     

浅谈DAB数字广播与AM中波广播技术路线

本文旨在探讨DAB数字广播与AM中波广播的基本概念、工作原理、发射和接收方式的区别,收听体验分析和终端经济性分析以及在推广方面的优缺点。     

数字调频广播

频率调制的原理比较简单，在任何时候，发射的载波都被调制信号按一定比例调制。频率的改变量作为偏移箱对载波既可显正极性，显负极性，该取决于是信号的极性。     

渐渐走来的DAB数字广播收音时代

收音机的历程 自从第一台收音机诞生到现在，收音机陪伴人们跨过了整整一个世纪。1902年，美国进行了第一次无线电广播，那时用的是矿石收音机。到二十世纪三、四十年代笨重的电子管收音机是富贵人家的装饰品。随着五十年代晶体管出现，收音机的体积、体型和重量都大大的减低，而且价格也比较平民化，收音机进入了辉煌时期。即使在六十年代电视机渐渐普及化，收音机和空中广播还是人们津津乐道的主要生活消遣。     

调频频段数字音频广播(CDR)在广东省的探索和实践

调频频段数字音频广播(CDR)是我国具有自主知识产权的数字音频广播标准,2012年,广东省率先在深圳、广州两地开展了示范网的申报、建设和测试工作,为CDR标准的产业化积累了宝贵的经验。本文介绍了广东示范网建设和测试的各项工作情况,并对我国数字音频广播事业的发展提出了自己的建议。     

Combining digital and analog signals for US IBOC FM broadcasting

IBOC DAB (In-Band On-Channel Digital Audio Broadcasting) requires the simultaneous broadcast of an analog and a digital signal within one channel of the FM band. Because broadcasters are adding IBOC to their existing systems, it is vital that they achieve maximum power efficiency while working within their existing space and power limitations. There are currently three different strategies proposed for accomplishing this goal, each having its own advantages and disadvantages. One strategy is to establish a separate, second antenna for the digital service. The other two strategies involve combining the analog and digital signals, either in a single hybrid transmitter or at the output of separate analog and digital transmitters. This paper discusses the equipment required for accomplishing this last strategy.     

Postcanceling techniques for simultaneous broadcasting of analog FM and digital data

We consider simultaneous broadcasting of low-power digital data and analog FM and present reliable receivers for the digital data. Due to the relatively low power level of the digital data and the interference suppression capability of analog FM, standard analog FM receivers can reliably recover the analog FM audio signal. To recover the digital data, an extended Kalman filter front end is developed that exploits the capture capability of analog FM to reconstruct and postcancel the analog FM component from the received composite signal. Simulations are conducted with artificial analog FM signals, suggesting that postcanceling schemes can provide higher data rates than their precanceling counterparts, at a lower transmission delay penalty but higher digital receiver complexity. For analog FM to digital signal power level ratios in the range of 30-50 dB, the postcanceler digital signal recovery appears fairly robust, providing digital signal-to-noise ratios of 2-7.5 dB. The corresponding uncoded bit error rates strongly depend on the power level difference between the host analog FM and the digital data signal. In particular, at 260 kb/s and E/sub b//N/sub o/=10 dB they range between 1% to about 15%, and can be reduced to acceptable levels using standard channel coding techniques.     

Simultaneous broadcasting of analog FM and digital audio signals bymeans of adaptive precanceling techniques

A method for broadcasting digital audio simultaneously with existing analog frequency modulation (FM) radio is presented. The method is based on precomputing the response of the host analog FM signal at the digital receiver and precanceling it at the transmitter. As a result, the digital transmission is free from interference from analog FM. We select the rate and power level of the digital transmission in a manner that the interference the digital data incur on the analog FM signal remains at acceptably low levels. The digital transmission is based on adaptive orthogonal frequency-division multiplexing (OFDM) (adaptive multicarrier). The frequencies and number of carriers of the digital multicarrier modem are judiciously selected in a time-varying fashion so as to cause a negligible distortion in a standard receiver for analog FM. Simulations based on conservative nonoptimized signal design indicate that data rates up to about 130 kb/s inside the 200-kHz FM channel are achievable for acoustic test signals. We present a number of numerical examples where the average digital data use up to 50% of the 200-kHz power spectrum with digital signal power levels 25-35 dB below the analog signal. Due to the resulting variable-rate digital transmission, a control channel is required. A method of precanceling with multiple orthogonal direct-sequence spread-spectrum schemes is also presented     

Comparison of analog and digital integrate-and-dump filters

The performance of the synchronized analog integrate-and-dump filter is compared with an equivalent digital implementation. Degradation in the output SNR of the digital filter due to sampling is computed. A first order prefilter is assumed and quantization noise is neglected.     

新型1 550 nm光发射机工程应用

为完成市、县级有线广播电视网的建设,应统一规划、合理布局、有序发展、符合标准、保证质量,网络建设起点要高,采用的技术要先进,网络规划设计要能适应逐步升级,新建和旧有线广播电视网络的改造,均应具备宽带、双向、高速和综合功能,并以HFC网络方式入户.在网络结构中特别提出县级市至所辖乡镇之间联网有两种模式:(1)采用工作波长为1 550nm的光收发设备和光功率放大(EDFA),以模拟方式传输,组成星型网;(2)经济和地理条件较好地区,采用SDH方式传输,全网由一个或几个自愈环网组成.     

FM IBOC DAB系统抗信道干扰技术研究

介绍了FM IBOC DAB系统中抗第一邻频干扰和无线信道噪声、衰落等干扰的主要技术,包括加扰、CPPC码纠错、交织和正交频分复用调制,最后提出了一些新的抗干扰措施,进一步提高了信道的鲁棒性能。     

Interference coordination for LTE-Advanced and FM broadcasting interoperability

The surest way to guarantee that multiple wireless systems can concurrently exist harmlessly, when operating in the same or adjacent channel, is by analyzing spectrum overlapping. This paper proposes a more accurate model to evaluate the interference power from co-channel and adjacent channel of orthogonal frequency division multiplexing-based long term evolution-advanced (LTE-Advanced) towards broadcasting frequency modulation systems at 800?MHz. Power spectral density overlapping factor is employed, and closed form of the interference power loss is derived. Numerical results demonstrate that the proposed method evaluates more exact interference power than the advanced minimum coupling loss (A-MCL) method, where the co-channel and adjacent channel interference powers are reduced by 1.3 and 3?dB, correspondingly, compared to that obtained using the A-MCL method. This decreases the minimum separation distance between the two systems, which can eventually lead to efficient radio spectrum resources utilization.     

Testing of digital television broadcasting from the stratosphere

Digital TV broadcasting from the stratosphere was tested using an unmanned aerial vehicle, a Pathfinder Plus. A television transmitter installed under the wing transmitted a UHF band signal as the vehicle flew at an altitude of 20 km. The Japanese digital terrestrial broadcasting standard (ISDB-T) was used for transmission. The 13.5-hour flight time included 3 hours of transmission testing. The transmitting equipment worked as expected in spite of the cold and low-atmospheric-pressure environment. Reception at the ground station was satisfactory even when the ISDB-T parameter set used was the one least robust under poor channel conditions.     

Robust modem and coding techniques for FM hybrid ICOC DAB

The design of robust modem and FEC (forward error correction) code techniques with application to the transmission of an FM hybrid analog/digital in-band on-channel (IBOC) digital audio broadcast (DAB) signal is presented here. The FEC codes are derived from an original lower rate convolutional code (R=1/3). The original code is segmented into a pair of “complementary” components, which form independent codes, each with a higher rate (less redundancy) than the base code. The exploitation of channel state information (CSI) and special interleaving techniques are described for application to FM hybrid IBOC DAB with its unique interference environment and selective fading due to multipath. Simulation results confirm the robustness of the design