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一、引言为了对付短波范围内无线电传输时的衰落现象,考虑了原有的各种分集方案。在语言通信中,由于通常是双向的,传输延迟必须在一定程度以下,目前主要是使用频率分集或空间分集系统。与此相反,在数字传输中多数是单向通信,而且传输延迟大多允许在数秒的程度。因此,采用时间分集系统是可能的。这里,作者特别以短波段数字传输为对象,根据上述观点,将频率分集和时间分集进行混合,提出了对选择性衰落和平坦衰落都能防御的一个简单而现实的分集方案,并对它进行了分析及部分的实验,现报告如下。
I. INTRODUCTION In order to deal with the fading phenomenon of radio transmission in the short-wave range, various original diversity schemes have been considered. In speech communication, since the transmission is usually bi-directional, the transmission delay must be below a certain level. At present, mainly frequency diversity or space diversity systems are used. In contrast, the majority of digital transmissions are one-way communications, and transmission delays are mostly allowed to be seconds. Therefore, the use of time diversity system is possible. Here, the author is particularly interested in the short-band digital transmission. Based on the above viewpoints, the frequency diversity and the time diversity are mixed, and a simple and realistic diversity scheme that can defend both selective and flat fading is proposed and implemented The analysis and some experiments are as follows.