16.若抽樣速率fS＜2fH，則會產(chǎn)生(      )

A.疊加失真                                                      B.混合失真

C.相對失真                                                      D.混疊失真

17.理想抽樣頻譜的包絡(luò)是(      )

A.一條曲線                                                      B.一條水平線

C.一條垂線                                                      D.一條斜線

18.在PCM中，對于語音、圖像等隨機信號，量化誤差是(      )

A.隨機的                                                         B.固定的

C.預(yù)知的                                                         D.可計算出來的

19.在脈沖編碼調(diào)制過程中，每增加一位編碼位數(shù)，平均量化信噪比就提高(      )

A.9dB                                                              B.8dB

C.6dB                                                              D.3dB

20.增量調(diào)制可看成是量化電平數(shù)為2的(      )

A.PCM                                                            B.DCM

C.TCM                                                             D.DPCM