بخش دوم. spectrum (or Fourier spectrum) of x( t ). magnitude spectrum of x(t), phase spectrum...

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دوم ش خ ب

Transcript of بخش دوم. spectrum (or Fourier spectrum) of x( t ). magnitude spectrum of x(t), phase spectrum...

Page 1: بخش دوم. spectrum (or Fourier spectrum) of x( t ). magnitude spectrum of x(t), phase spectrum of x(t).

دوم بخش

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spectrum (or Fourier spectrum) of x( t ).magnitude spectrum of x(t),

phase spectrum of x(t).

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THE FREQUENCY RESPONSE OF CONTINUOUS-TIME LTI SYSTEMS

frequency response of the system

Example:

و سیستم ویژه تابع بینیم می هم باز شد گفته هم قبال که H(w0)همانطورآنست ویژه مقدار

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Example:

Example:

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Example:

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Example:

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Fourier Transform Applications

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FILTERING

Ideal Low-Pass Filter (LPF)

Ideal High-Pass Filter (HPF)

(LPF) (HPF)

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Ideal Bandpass Filter

(BPF)

(BPF)

Ideal Bandstop Filter

(BSF)

(BSF)

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Sampling Systems

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The extremely useful sampling theorem, also known as the Nyquist theorem, or the Shannon theorem, gives a sufficient condition to recover a continuous-time signal from its samples

The Sampling Theorem

Ideal lowpass filter usedto recover the continuous-time signalfrom the impulse train sampled signal.

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Sampling Using a Sample-and-Hold Operator

sample-and-hold (SH)

Simplified sample-and-hold circuit

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The theoretical representation of a sample-and-hold shown in following Figure consists a) sampling operation (multiplication by an impulse train), b) followed by filtering with a linear time-invariant (LTI) system of impulse response h0(t),

which is a unit pulse of duration equal to the sampling period Ts.

Note that the sample and-hold operator is sometimes called zero-order-hold (ZOH), although here we call zero-order-hold only the LTI system block with impulse response h0(t) in following Figure .

Effect of sample-and-hold operator on an input signal

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ZOH systemیادآوریضرب ZOHدیدیم شامل

فیلتری از عبور و ضربه قطاربود مستطیلی ضربه پاسخ با

حوزه در آن مفهوم کهمی بررسی را فرکانس

کنیم:

بازسازی برای فیلتر این معکوسلذا است نظر مورد سیگنال

: یابیم می آنرا معکوس

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Signal reconstruction from the output of the sample-and-hold

Frequency response of the reconstruction filter.