(1)　　在某些无线信道中，多普勒频移会引起无线信道输出信号的混叠。请描述产生混叠的各种原因；
(2)　　无线信道中的多普勒谱有一种经典谱(classic spectrum)，请解释产生这种谱形状的机理；
(3)　　请用Simulink工具编写代码(S-Function方式)，产生一单径瑞利信道，其多普勒谱为经典谱，其中移动速率为120km/h。并请回答：证明自己用计算机产生的经典谱是正确的可能方法。
,(1) in certain wireless channel, the Doppler frequency shift will be caused by wireless channel output signal aliasing. Please describe the resulting aliasing of a variety of reasons　(2) wireless channel Doppler spectrum there is a classical spectrum (classic spectrum), please explain such a spectral shape of the mechanism　(3) Please use Simulink tools for writing 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 please answer: prove that they used computer-generated classical spectrum is correct possible ways.