M进制，$k=log_2M$
$$S_{MPSK}=Acos(w_ct+varphi _i) \ varphi _ i=frac{2pi i}{M} qquad i=0,1,cdots,M-1$$
$$S_{MPSK}=g(t)cos(w_ct+varphi _i)=g(t)a_{ic}cosomega_ct - g(t) a_{is} sin omega_s t $$
常记溪亭日暮，沉醉不知归路。兴尽晚回舟，误入藕花深处。争渡，争渡，惊起一滩鸥鹭。
