[工學(xué)]信號(hào)與系統(tǒng)課件 課堂版chap-文庫(kù)吧
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【正文】 ms 167。 Transformations of the independent variable 167。 Examples of transformations of the independent variable 1. Time shift( 時(shí)移 ) 0ttt ??0nnn ??? ? ? ?0ttxtx ??? ? ? ?0nnxnx ??Example 1 ? ??tx1/tt 10 tt ??0 otherwise Please indicate ? ?0ttx ?16 Chapter 1 Signals and Systems ? ?0ttx ? ??tx 與 波形相同 00 ?t 相當(dāng)于 左移（超前） to ??tx2. Time reversal( 時(shí)域反折 ) tt ?? nn ??x(t) is a reflection of x(t) about t=0 00 ?t ??tx相當(dāng)于 右移（延遲） to 時(shí)移對(duì)信號(hào)的影響 17 3. Time scaling( 尺度變換 ) Chapter 1 Signals and Systems ? ? ? ?atxtxatt ???a1 信號(hào)壓縮 a倍 0a1 信號(hào)擴(kuò)展 1/ a 倍 ① Continuous time signals ② Discrete Time signals x[ an] n, an ∈ N n1? 0 1 2312x[n] 18 Chapter 1 Signals and Systems 0 1 2 t ??tx1 Solution Example Given the signal 312xt????????2/3 0 2/3 t 1 3 12xt????????19 167。 Periodic signals Chapter 1 Signals and Systems Synthesize the signal39。s periodic ??tx1 T1 ??tx2 T2 當(dāng) T1/T2為有理數(shù)時(shí)， 為周期的 ? ? ? ?tbxtax21 ?2211 TnTnT ??其中 n1,n2 互質(zhì) 其周期 20 Chapter 1 Signals and Systems 167。 Even and Odd Signals ? ? ? ?? ? ? ?? ?txOdtxEvtx ??—— Even part ? ?? ? ? ? ? ?? ?txtxtxEv ???21—— Odd part ? ?? ? ? ? ? ?? ?txtxtxOd ??? 210 1 2 t ??tx1 21 Chapter 1 Signals and Systems 167。 Exponential and Sinusoidal Signals 指數(shù)信號(hào)和正弦信號(hào) 167。 ContinuousTime Complex Exponential and Sinusoidal Signals ? ? stCetx ? ?????? t1. Real Exponential Signals ? ? atCetx ?a is real 22 Chapter 1 Signals and Systems 2. Periodic Complex Exponential and Sinusoidal Signals ① Period ② Euler’ s relation ③ Average Power ④ Harmonic relation 3. General Complex Exponential Signals 23 Chapter 1 Signals and Systems 167。 DiscreteTime Complex Exponential and Sinusoidal Signals ? ? nCnx ?? ?????? n1. Real Exponential Signals a?? real ? ? nanx ?24 Chapter 1 Signals and Systems 2. Complex Exponential Signals and Sinusoidal Signals ① Average Power ② Euler’ s relation ④ Periodicity Properties ⑤ Harmonic relation ③ Frequency Properties 3. General Complex Exponential Signals 25 Chapter 1 Signals and Systems ( a) ω0=0
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