一、引言要进一步扩大民用地面移动电台的应用,特别是在甚高频和特高频段的通讯,将完全取决于更为有效地利用无线电频谱。充分利用频谱的较好的技术有信道分配技术多用低冗余度的数据传输和收发分集技术。对给定的服务等级来说,改变调制制度,例如把调频或调幅制改为其它更能利用频谱的调制制度也是很有意义的。不难看出,在目前各种调制制度中,唯有单边带才能使信息传输速率接近香农极限。其余方式都不好,有的甚至很糟糕(最明显的是各种形式的调频和纯载波调幅)。这种简单的分 I. INTRODUCTION The further expansion of the use of civilian terrestrial mobile stations, especially in the VHF and UHF bands, will depend entirely on the more efficient use of the radio frequency spectrum. Better technology to make full use of the spectrum channel allocation technology and more low-redundancy data transmission and transceiver diversity technology. For a given level of service, it would also make sense to change the modulation system, for example to change the FM or AM system to other modulation systems that make better use of the spectrum. It is not hard to see that in the current various modulation systems, only the single sideband can make the information transmission rate approach Shannon’s limit. The rest of the way is not good, some even very bad (most obvious is the various forms of FM and pure carrier AM). This simple points