第4章模擬信號(hào)的數(shù)字化

1、12模擬信號(hào)s(t)模擬信號(hào)的抽樣3)()()()(kTsttstsTk)()()(ffSfSknsnffTf)(1)(4)(1)()(1)(snsknffSTnfffSTfSnsnffTf)(1)()()()(ffSfSkHsff256)1 (222nkBnkBBfs3BB2B4B5B6BfL0fs7（a) 基帶信號(hào)(b) PAM信號(hào) (c) PDM信號(hào)(d) PPM信號(hào)圖4.2.6 模擬脈沖調(diào)制8圖4.3.1 抽樣信號(hào)的量化iiiqmkTsmqkTs)(,)(1當(dāng)9Mabv/)(viamiMimmqiii,.,2 , 1,2110baMimmkkikkkqkqkqiidssfqsdssfs

2、sssEN12221)()()()()(viami2vviaqibakkkkdssfssES)()(2211avMvadsavviasdsaqsdssfqsNMiMiviaviakkMimmkikMimmkkikqiiii24122121)2(21)()()(3121)1(2121211 avM2122vNqaakkvMdsasS222)(12212MNSqMNSdBqlg2012ydxdyxyydydxxNy1dydxNydydxx113dydxNydydxx1xNdydxckyxlnkkyxlnxkyln111411,ln1ln110,ln1xAAAxAxAAxy1516A律和律和13折線

3、法比較折線法比較i 8 7 6 5 4 3 2 1 0y =1-i/8 0 1/8 2/8 3/8 4/8 5/8 6/8 7/8 1A律律x值值 0 1/128 1/60.6 1/30.6 1/15.4 1/7.79 1/3.93 1/1.98 113折線法折線法 0 1/128 1/64 1/32 1/16 1/8 1 x=1/2i折線段號(hào)折線段號(hào) 1 2 3 4 5 6 7 8折線斜率折線斜率 16 16 8 4 2 1 從表中看出，從表中看出，13折線法和折線法和A = 87.6時(shí)的時(shí)的A律壓縮法十分接近。律壓縮法十分接近。171ln1lnxy25512255125625512568/

4、iiyx181920、217654321345676011 100 101 110 111 1103.153.965.006.386.806.42抽樣值量化值二進(jìn)制符號(hào)抽樣保持量化編碼解碼低通濾波編碼器解碼器模擬信號(hào)輸入PCM信號(hào)模擬信號(hào)輸出22量化值序號(hào)量化電壓極性自然二進(jìn)制碼折疊二進(jìn)制碼15141312111098正極性111111101101110010111010100110001111111011011100101110101001100076543210負(fù)極性01110110010101000011001000010000000000010010001101000101011001

5、1123段落序號(hào)段落碼c2 c3 c481117110610151004011301020011000量化間隔段內(nèi)碼c5 c6 c7 c81511111411101411011211001110111010109100181000701116011050101401003001120010100010000024)2(B/fH2 Nq / S2526相加器kkkkkkkkksssssesrs*piikiksas1*27rks*k28kkkkkkkkkrersesssq)(*vMMv2) 1(,) 1(2+-vv0vM1M2M3M4圖4.5.2 , 和M之間關(guān)系vqfk1)(292/2/222/

6、2/2212)(1)()(vvkkvvkkkkvdqqvdqqfqqEssqffNfvfP0,12)()(2 sLLqqffNvffPN12)(230tAtm0sin)(tAdttdm00cos)(sfTA/00max/sfA2022220222max822fffASss312022220222max822fffASssvM2) 1(20222220222232) 1(821ffvMffvMSssLsqfffMNNS203228) 1(33233sk*抽 樣二電平量化s(t)skekrksk延 遲rksk*(a) 編碼器 (b)解碼器延 遲34(a) 編碼器(b)解碼器積分器抽樣 判決s(t)e(t)d(t)s(t)積 分d(t)低通T(t)s(t)輸出二進(jìn)制波形35輸出二進(jìn)制波形36(a) 基本量化噪聲(b) 過載量化噪聲37sfTk/38eef,21)(321)()(2222deedeefeteEssffffP0,3)(2sLLqffffPN3)(239tAts0sin)(tAdttds00cos)(sfT0A0maxsfA2022220222maxmax822fffASssLsLssqfffffffNS2032220222max833840人有了知識(shí)，就會(huì)具備各種分析能力，明辨是非的能力。所以我們要勤懇讀書，廣泛閱讀，古人說“書中自有黃金屋?！蓖ㄟ^閱讀