ELEC211 notes
ELEC202 L7-12
L7-8 PM 和 FM
PM 和 FM 的输出信号是无法区分的,都是变频。但是同样的输入信号会得到不一样的输出信号。
PM:频率变化的导数 = 相位 = 信号


FM:相位变化的积分 = 频率 = 信号。


调制区别:

FM比较常用所以多半考FM。
Frequency/modulation sensitivity:频率/调制灵敏度
Frequency deviation:频率偏差(实际频率与中央频率之差) = frequency
sensitivity * max(message) =
Frequency swing:= 2*Frequency deviation
Modulation index :调制指数 = maximum frequency deviation / baseband
bandwidth =
FM bandwidth:
若
若
L9 Digitisation
采样,老东西
预防混叠:
•Pre-filtering prevents aliasing happening by limiting the signal bandwidth. •Post-filtering mitigates the effects of aliasing by removing the corrupted portion of the spectrum. •Pre-filtering is more effective.
数字化 Digitisation: sampling + quantisation

Dynamic Range = 最大范围/最小量化 =
Non-uniform quantisation 非均匀量化
v1.4.14