說明：  2. 關于無線信道的多普勒譜，請回答以下問題： (1) 在某些無線信道中，多普勒頻移會引起無線信道輸出信號的混疊。請描述產生混疊的各種原因； (2) 無線信道中的多普勒譜有一種經典譜(classic spectrum)，請解釋產生這種譜形狀的機理； (3) 請用Simulink工具編寫代碼(S-Function方式)，產生一單徑瑞利信道，其多普勒譜為經典譜，其中移動速率為120km/h。并請回答：證明自己用計算機產生的經典譜是正確的可能方法。
(On the wireless channel of the Doppler spectrum, please answer the following questions: (1) In some radio channels, the Doppler frequency shift will cause the output signal of the wireless channel aliasing. Please describe the aliasing produced a variety of reasons (2) wireless channel in the Doppler spectrum has a classical spectrum (classic spectrum), please explain the mechanism of produce such spectral shape (3), please use the Simulink tool to write code ( S-Function mode), resulting in a single-path Rayleigh channel, the Doppler spectrum for the classical spectrum, including mobile rate of 120km/h. And requested the answer: that they used computer-generated classical spectrum is the right possible way.)