精品課程大學(xué)物理-信號(hào)與系統(tǒng)(存儲(chǔ)版)
【正文】 多是隨機(jī)信號(hào)（新信息）： 耗電、打電話等 Deterministic and Stochastic (nondeterministic) Signals 確定性信號(hào)隨機(jī)信號(hào) (非確定性信號(hào) ) ? Even signal A signal x(t) or x[n] is referred to as an even signal if it is identical to its timereversed counterpart, ., with its reflection about the origin. In continuous time a signal is even if ? ?tftf ee ??)(Odd and Even Signals while a discretetime signal is even if ][][ kfkf ??? Odd signal A signal is said to be odd if ][][ kfkf ???)()( tftf ???In continuous time In discrete time )()()( tftftf eo ??)]()()()([21)( tftftftftf ???????)]()([21)]()([21 tftftftf ??????)()( tftf oe ??Odd and Even Signals In fact, any signal f(t) can be expressed as a sum of its even part and its odd part, that is )]()([21)( txtxtx e ???)]()([21)( txtxtx o ???Even part: Odd part: So: 11 0t21f ( t )t11 021f ( ? t ) t11 0fe( t )t11f0( t )Example:Determine the even and odd parts of the signal f(t) given by Buildingblock signals (典型信號(hào) ) 正弦信號(hào) sine signals 指數(shù)信號(hào) exponential signals 沖激信號(hào) impulse signals 階躍信號(hào) step signals sine signals )s i n ()( 0 ?? ?? tAtft A ? A 0???exponential signals指數(shù)信號(hào) tAetfa?)(At0a0aReal Exponential Signals ????? ?0 00,0 )(ttAetf t aata/1A則？若 ,0,)( ? ? aa tAetf Eternal, plex exponentials 指數(shù)信號(hào) For is plotted for different values of s superimposed on the plex splane. tAetfIAetf tst ?? s i n)]([,)( ??Complex Exponential tjetf 0)( ??復(fù)指數(shù)信號(hào)的基波周期： 0/2 ???TEuler’s relation： )(21)c o s ( tjtj eet ??? ???)(2 1)s i n ( tjtj eejt ??? ???if f(t)=K ?? t ? Sinc function/signals ttt /s in)(Sa ?1)0(Sa ??2,1,0)(Sa ???? kk ??????dtt )(Sa1????2 ?3t)(Sa t? Singularity Functions 奇異信號(hào) 即本身、其導(dǎo)數(shù)或其積分有不連續(xù)點(diǎn)的 函數(shù)?？杀硎緸? ( 1 )( ) ( ) ( )ty t f d f t?? ?????產(chǎn)生另一個(gè)連續(xù)時(shí)間信號(hào)，其任意時(shí)刻 t的信號(hào)值 為 f(t)波形在 (∞, t)區(qū)間上所包含的凈面積。 根據(jù)牛頓第二定律 ， 有 dttdmtmatf )()()( ???)(1)(39。 若要求解 n階微分方程 ， 還需要給定 n個(gè)初始條件 y(0)， y′(0)， … , y(n1)(0)。 22139。 )(ty f)(tyxDescription of systems Systems process input signals to produce output signals. 連續(xù)系統(tǒng)輸入輸出方程 例 簡(jiǎn)單力學(xué)系統(tǒng)如圖所示 。 例：尺度變換變換后語音信號(hào)的變化 f (t) f () f () ? reflection f(t) ? f(?t) 1t2 4f ( t )??? ????其它 042 2/)2()(tttf??? ???????其它 042 2/)2()(tttf??? ???????其它 024 2/)2( tt1t? 4f ( ? t )? 2f(?t)表示將 f(t)以縱軸為中心作 180?翻轉(zhuǎn)。 21 /TT例： Page 6 Deterministic and Stochastic (nondeterministic) Signals Definitions 信號(hào)的未來值可以用時(shí)間變量的數(shù)學(xué)關(guān)系式準(zhǔn)確描述的信號(hào)稱為 確定性信號(hào) 。 Systems信 號(hào) 與 系 統(tǒng) CHAPTER 1 INTRODUCTION Contents ?Description amp。 一段語音信號(hào) (―對(duì)了” ) 。 – Ramp Signal 斜變信號(hào) – Unit Step Signal單位階躍信號(hào) – Signum Function符號(hào)函數(shù) – Unit Impulse Signals單位沖激 Unit Ramp Signal 單位斜變信號(hào) 0 1 t 0 t0 t0+1 t R(t) R(tt0) t =0 R(t) = t t 0 R(t) = 0 t t0 R(tt0) = 0 t = t0 R(tt0) = t t0 Unit Step Signal 單位階躍信號(hào) ????????02100010)(tttttttt?1 ???????00100)(21 tttt?t 0 t0 1 epsilon 用階躍表示門信號(hào) )2()2()( ????? ???? tttp )2()2()( 000????? ??????? ttttttp2?2?? t t 0t（ 1）突然接入的直流電壓 （ 2）突然接通又馬上斷開電源 K 負(fù)載 Signum Function 正負(fù)符號(hào)函數(shù) Definitions sgn(t) 1 0
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