1、3.1 3.1 周期信号的分解与合成周期信号的分解与合成3.2 3.2 周期信号的频谱周期信号的频谱3.3 3.3 非周期信号的频谱非周期信号的频谱3.4 3.4 傅氏变换的性质与应用傅氏变换的性质与应用3.5 3.5 傅氏变换的性质与应用（续）傅氏变换的性质与应用（续）)2(T11n1n0)sincos()(ntnbtnaatf1n1n0)cos(ntnAaTttfTa00d)(1TnttntfTa01dcos)(2TnttntfTb01dsin)(22n2nbaAn0d)(100TttfTa0dcos)(2221TTnttntfTa2011201221cos4dsin4dsin)(2TTT
2、TnntnTAttnATttntfTb),5,3,1(4nnA),6,4,2(0n)5sin513sin31(sin4)(111tttAtftAtAtAatf13121103cos2coscos)(2eecosjjxxx)e(e2)e(e2)(1111j2j22jj10ttttAAatf3,2,1e21jn0nAantn，ntnFtf1jne)(2T2T-jnnde)(121ttfTAFtn2T2Tjnnnde)(2j1-tnttfTbaA2nn00AFaF，2T2T-jnde)(11ttfTFtn)5,3,1(j2de22T0j1nnAtATtn000 aF)5,3,1(ej2A)(1jnn
3、tfntnnnTtt)()(TTttTFtn1de)(12T2T-jn1ntnTt1jTe1)()5sin513sin31(sin4)(111tttAtf)23cos(31)2cos(411ttA)2()2sin(TdeT11122-jn1nnAtAFtn2tA20t)(tf)2(SaT1nAtttsin)(Sa1)0(Sa)3,2,1(kkt21fT21ttfTFTTtnde)(122jn1ntnFtf1jne)(ttfTFnFTTtnde)()(22jn11ttfFtde)()(jde)(21)(jtFtf)2(Sa)2()2sin(de)(22-jtFt21t20t)(tG1de)()(
4、-jttFt1)(t)(21j1de)(0)j(tFtj1)(ett)0,0(e)(ttftj1)()(F)(2j1)(21)(2)sgn(tt)()(),()(2211FtfFtf若)()()()(22112211FaFatfatfa则j2)()(Ftf若)(1)(aFaatf则)()(Ftf若0j0)()(teFttf则)(je)()(FF)(jj00e)(e)(ttFF)()()()(TtGTtGtGtf)2sin()23sin()2Sa()cos21)(2Sa()ee1)(2Sa()(jjTTTFT-T)()(Ftf若)()(0j0 Fetft则)()(21cos)(000FFttft
5、tgtf0acos)()(2)(Sa2)(Sa2)(00aFntnFtf1jne)(e)(1jnntnFF F)(21nnFn)()(jsin)()(cos000000ttnnnTF)-()2Sa(2)(11)2(Sa)2Sa()2Sa()(22F)()()(tGtGtf)()(),()(2211FtfFtf设)()()()(2121FFtftf则)()()()()()(HFYthtfty-jde)()(tthHt)(*)(21)()(2121FFtftf)()(Ftf若)(j)(Ftf则j)(t1j1)(j)()(tt)()(Ftf若d)(tf则0)(,j)(0FF0)(,j)()()0(0FFFttfFFd)()0()(0d)(21d)(22Fttf
