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本文论述了加重电路参数与信噪比、门限电平等传输性能指标之间的关系,给出用计算机算得的若干曲线,并提出最佳预加重电路的建议和试验结果。采用本文建议的预加重特性,可使图象加权信噪比比用CCIR 405-1加重时改善2.5～3dB,而微分增益、微分相位等性能则基本不变,且适应于不同带宽的中频滤波器。文中对AIAA 7th Communications Satellite SystemsConference(1978)有关文献中论及的最佳预加重网络也作了一些比较。此外,文中给出了电视线路门限电平与中频等效噪声带宽关系的计算曲线;还综合若干试验结果,提出了最佳频偏选取的经验公式。
This paper discusses the relationship between the emphasis of the circuit parameters and the transmission performance such as signal-to-noise ratio and threshold level, gives some curves calculated by computer, and puts forward the suggestions and test results of the best pre-emphasis circuit. Adopting the pre-emphasis feature proposed in this paper, the image-weighted signal-noise ratio can be improved by 2.5 ~ 3dB compared with that of CCIR 405-1, while the performance of differential gain and differential phase are basically the same, and are adaptive to IF filters with different bandwidths Device. The text also compares some of the best pre-emphasis networks discussed in the AIAA 7th Communications Satellite Systems Conference (1978). In addition, the calculation curve of the relationship between TV line threshold level and IF equivalent noise bandwidth is given in this paper. Based on several experimental results, the empirical formula of optimal frequency offset selection is proposed.