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卫星的模拟遥测付载波信道是采用FSK调制方法,它传递的主要信息是脉冲沿的时间,而这些脉冲出现的时间又是变化的,因此也类似于PPM-FM调制方式。在解调过程中采用加大视频带宽的办法,可以提高判决时间的精度。但是,带宽的加大将使通道信噪比降低,误判概率则大大增加,因此必须选择合适的视频带宽。 本文重点讨论交叉电平捡出方式的原理及优点,其时间判决精度和误判概率均比固定电平判决优越。
Satellite analog telemetry subcarrier channel is the use of FSK modulation method, the main message it passes is the pulse edge time, and these pulses appear again in time and therefore similar to the PPM-FM modulation. In the demodulation process by increasing the video bandwidth approach, you can improve the accuracy of the decision time. However, the increase of the bandwidth will make the signal to noise ratio of the channel lower, the misjudgment probability will increase greatly, so must choose the suitable video bandwidth. This article focuses on the principle and advantages of the cross-level detection method, and the accuracy of the time decision and the false positive probability are both superior to the fixed-level decision.