以往,曾为高数据速率工作而研制出了几种使用移頻键控和差动相干移相键控的多路调制解调器,它们在良好的传播条件下,确实能够有效地工作。又曾为抗多径效应或抗严重干扰而特别设计的,如林肯实验室研制的瑞克(RAKE)设备,这种设备在低劣的传播条件下也能够可靠地工作;然而,在比较良好的条件下,它的不可改变的低数据 In the past, several multi-mode modems using frequency-shift keying and differential coherent phase-shift keying have been developed for high data rate work and are indeed capable of operating effectively under good propagation conditions. It has also been specifically designed for resistance to multipath effects or severe interference such as RAKE equipment developed by Lincoln Laboratories that operates reliably under poor propagation conditions; however, Under the conditions, it’s immutable low data