当前,短波通信日益拥挤,在环抱地球的信道空间存在着密集而强大的干扰.特别是进入电子对抗以来,通信机构有了明显的变化,较显著的是这些方面:自动化、自适应、由恒参量转入变参量、由单工转入双工、由单频段转入双频段、由单一调制转入多种调制、实现信息保密、载频捷变或抑制 At present, shortwave communications are increasingly crowded and there is intensive and powerful interference in the channel space surrounding the earth, especially since the entry into the electronic warfare. There have been notable changes in communication agencies, notably in these areas: automation, adaptation, Parameters into variable parameters, from simplex to duplex, from single-band into dual-band, from a single modulation into a variety of modulation, information confidential, agile or carrier frequency suppression