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在VHF/UHF频段地面移动通信中,由于基地台和移动台之间电波的多径传播和随着移动台的行走,将产生剧烈的衰落现象。在800兆赫频段的汽车电话系统中,当车速为50公里/小时时,这种衰落率大约为40赫。因此在通话中,就产生脉冲性噪音,造成非常刺耳的干扰声。本文说明应用音节压扩器作为对付它的方法是有效的,阐述丁关于800兆赫频段汽车电话系统的应用条件和改善通话质量的效果。研究结果,以压缩比为2、时间常数为20毫秒的基准电平当作标准调制电平。此时,对在衰落情况下的热噪音和同信道干扰,可以得到好的改善效果,肯定了应用在汽车电话系统中的有效性。
In VHF / UHF terrestrial mobile communications, fading due to multipath propagation of radio waves between the base station and the mobile station and as the mobile station travels. In the 800 MHz car phone system, this decay rate is about 40 Hz at a speed of 50 km / h. So during a call, it produces pulsating noise, causing a very harsh interference noise. This article shows that the use of syllable compander as a countermeasure against it is effective, explaining the application of the 800 MHz band car phone system and improving the quality of the call. As a result, the reference level with a compression ratio of 2 and a time constant of 20 milliseconds was taken as the standard modulation level. In this case, good effects can be obtained for thermal noise and co-channel interference in the case of fading, and the validity of the application in a car phone system is affirmed.