中文摘要：

短波通信信道具有频率选择衰落特性,相干带宽是描述单载波系统平坦衰落信道带宽的重要参数。提高相干带宽有利于系统使用更大的带宽来实现高数据速率传输并且有助于减少接收机的复杂度。该文提出一种利用发射端窄波束成形在空间上将发射能量集中于主路径且抑制其它路径信号来提高短波信道相干带宽的方法,并利用自适应技术来建立及保持点对点之间的窄波束通信。理论研究表明,该方法能有效地提高信道相干带宽。该文以中距离短波通信为例,计算了使用不同发射天线数时的相干带宽值,计算结果证实了该方法的有效性。

英文摘要：

Shortwave communication works with frequency-selective fading channel, of which coherence bandwidth is an important parameter describing the ＂flat＂ channel bandwidth to be used by single carrier system. As has been known, increasing the coherence bandwidth can facilitate larger bandwidth system with faster data rate transmission and simplified system with reduced receiver complexity. This paper proposes a method of using narrow beam to concentrate spatially the transmitted signal power on the main path and suppress the undesired multipath signals resulting in delay spread. For realizing the functions motioned above, the adaptive technique is taken to set up and maintain the narrow beam link for the point-to-point communication. The theoretical study shows that the coherence bandwidth can be effectively increased by this method. The calculations are performed for different number of antennas over the mid-range channel and the results confirm this approach.