基于低压配电网传输的公共广播系统（PAS）

【作者】 龚仕伟；

【导师】 许锦标；

【作者基本信息】 广东工业大学 ， 检测技术与自动化装置， 2003， 硕士

【摘要】 公共广播系统(Public Address System，简称PAS)是智能大厦、机场、车站、综合大楼等公共场所所必备的设备，其应用范围极为广泛。但是目前的PAS存在着布线量较大、系统维护不便和分区方式不灵活等缺点。本文要解决的问题是如何利用低压电力线作为PAS的传输介质，研制基于低压配电网传输的PAS，克服传统PAS在应用中存在的缺点。 文章首先对目前PAS的应用现状进行了简单介绍，提出基于低压配电网传输的PAS的研究设想，新的PAS具有免布线、维护方便、分区灵活和易于扩展等优点。同时，指出课题研究的难点主要在于电力线作为通信介质存在技术上的难度。 在对低压电力线路的噪声特性、衰减特性和阻抗特性三个方面充分分析的基础上，本文提出一种语音编码+扩频传输的系统总体方案，采用扩频载波(Spread Spectrum Carrier，缩写为SSC)技术克服电力线传输信号存在的问题，采用语音合成质量高并具有较低码率的MBE压缩算法完成语音信号的编解码。课题选用相关的产品完成了系统的硬件设计和软件设计。 本文对研制成功的实验系统进行了数据传输能力和语音传输质量的测试。通过对实验结果的分析可知影响数据传输能力主要有两个因素：发送信号的幅度和信号的载波频率。系统合成语音的质量较好，具有较高的清晰度和自然度。实验结果表明本设计方案合理，传输可靠，语音质量高，可以用于公共场所的语音广播，克服传统PAS的缺点。系统还需要在两个方面进行改进：(1)抵抗低压电力线恶劣通信状况的能力；(2)适合于音乐信号的传送。 系统的研制成功使得将来有可能在如下课题开展研究：基于低压配电网传输的音／视频系统，如内部电话系统或可视对讲系统。更多还原

【Abstract】 Public Address System(abbreviated as PAS) is a necessary equipment for public places such as intelligent building, airport, railway station and integrated building and has a wide range of applications. However, current PAS has the disadvantages such as requiring a large amount of wiring, inconvenient system maintenance and inflexible area-dividing mode. The objective of this paper is to utilize low-voltage power line as the transmission medium of PAS and develop a PAS based on transmission over low-voltage power distribution networks, in order to resolve the defects existing in conventional PAS.The paper made a brief introduction to present application status of PAS and brought up the idea of researching on PAS based on transmission over low-voltage power distribution networks. New PAS possesses advantages such as avoiding wiring, convenient maintenance, flexible area-dividing mode and readily expanding. Hindrance to Research is that the using of power line as a communication medium has technical difficulties.System scheme of Speech coding plus Spread Spectrum Communication was presented based on a full analysis of noise characteristic, attenuation characteristic and impedance characteristic of low-voltage power line. Spread Spectrum Carrier(abbreviated as SSC) technology is adopted to overcome problems existing in signal transmission over power line. High quality, low rate MBE compression algorithm was used to complete speech encoding and decoding. Relative products were selected to carry out system’s hardware and software design. The successfully developed experimental system was tested to evaluate the data transmission ability and speech quality of the system. Analysis of testing results showes that two factors mainly influence data transmission ability: transmitting signal’s amplitude and carrier frequency. Good speech quality is found to have high clarity and naturalness. Experimental results have demonstrated that the scheme is reasonable and can be used for public places addressing. The system requires two improvements: (1) the ability to counter the severe communication condition of low-voltage power line and (2) the ability to transmit music signal.The success of system study has made it possible to launch researches onVIfollowing topic: audio/video system based on the transmission over low-voltage power distribution networks, for example, internal telephone system or picture intercom system.更多还原