【单选题】某正弦电压的最大值为311V,周期为0.02s、初相为30°,则该正弦电压的表达式为
【单选题】What is an advantage of an externally modulated laser over a directly modulated laser?()
D.
higher dispersion tolerance
E.
higher optical signal-to-noise ratio
【判断题】The envelope of the AM signal can fully reflect the information of the modulated signal when the AM Ma is less than 1. ( )
【单选题】Which of the following signals carries modulated signal information ( ).
B.
L ocal oscillator signal
【单选题】以下手动变速器的作用中不正确的是 。 ( )