有线电视同轴电缆的传输特性

Transport Properties of a Coaxial Cable for the CATV

频率很高的有线电视信号在同轴电缆中传输 ,不能采用理想导线的集中参数理论进行分析 ,可将传输线看作一维分布参数电路。同轴电缆的特性阻抗、屏蔽衰减、衰减常数、回波损耗等电气性能 ,涉及到趋肤效应、电磁场、分布参数等物理机制。对电缆的电气参数产生的原因进行阐述 ,力求广电行业技术从业人员“知其然 ,亦知所以然”。

The transport properties of the high-frequency television signal in a coaxial cable can′t be analyzed by means of the concentrated-parameter theory in a conductor, but can be explained by regarding a cable as 1-dimension distribution parameter circuit. The electric properties of coaxial cable, such as its characteristic impedance, screening attenuation, attenuation constant, and loss of echo wave, are related to the physical mechanism of the skim effective resistance, electromagnetic field, distribution parameter. In order to let the workers in the industry of broadcasting-television know it, the explanation on the physical origin of the electric parameter of the coaxial cable is given in this paper.