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دوم بخش
spectrum (or Fourier spectrum) of x( t ).magnitude spectrum of x(t),
phase spectrum of x(t).
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
Example:
Example:
Example:
Example:
Fourier Transform Applications
FILTERING
Ideal Low-Pass Filter (LPF)
Ideal High-Pass Filter (HPF)
(LPF) (HPF)
Ideal Bandpass Filter
(BPF)
(BPF)
Ideal Bandstop Filter
(BSF)
(BSF)
Sampling Systems
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.
Sampling Using a Sample-and-Hold Operator
sample-and-hold (SH)
Simplified sample-and-hold circuit
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
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
Signal reconstruction from the output of the sample-and-hold
Frequency response of the reconstruction filter.