t 周期方波信号 t 周期方波信号 幅频图 相频图 幅频图 相频图 2T2T2T2T()xt()xt00305nAAA4A00305nA4A00305()00305()32252/20/2/20/2/20/2/20/20000141[(cos(2(cos()1)4,1,3,50,2()02()cos(n)02()sin(n)4sin(),4,6))|]TTTnTTnTTTaxtdtaxttdtbxttdtTTTTnTnnnnnnntdtt（x(t)奇函数）000411()(sinsin3si5)3...n5ttxtt/20/2/20/2/20/2/20/4/200/4/200000/40/4()02()sin(n)02()cos(n)4cos()4cos()co141(sinsin2[sin(sis())||n2)(TTTnTTnTTTTTTTTaxtdtbxttdtaxttdtnTTTTTnnTnnntdtntdtntdttt（x(t)偶函数）02sin)]()24,1,3,50,2,4,6nnTnnn因为000000411()(coscos3cos535411{sin()sin[3()]sin[5()]}232)2..5.ttxtt