lecture 2 · lecture 2: signals 1st semester 1439-2017. 2 signals in communication system. 3 what...
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Lecture 2:Signals
1st semester 1439-2017
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Signals in Communication System
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What Does a Signal Mean ?
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Classification of Signals
There are several classes of signals:
1. Continuous-time and discrete-time signals.
2. Analog and digital signals.
3. Real and complex signals.
4. Deterministic and random signals.
5. Even and odd signals.
6. Periodic and non-periodic signals.
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Classifications of Signals (Cont.)
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Classifications of Signals (Cont.)
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Classifications of Signals (Cont.)
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Classifications of Signals (Cont.)
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Classifications of Signals (Cont.)
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Classifications of Signals (Cont.)
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T
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Classifications of Signals (Cont.)
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Classifications of Signals (Cont.)
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Classifications of Signals (Cont.)
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Some Common Waveforms
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Sine Wave
A sine wave can be mathematically describe as
s(t) = A sin (ωt + φ)
where
A is the peak amplitude
ω is the angular frequencyω = 2πf f is frequency in Hertz ,
φ is the phase.
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Peak Amplitude
The peak amplitude of a signal is the largest value it takes, proportional to the energy it carries.
For electric signals, peak amplitude is normally measured in volts.
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Period and Frequency
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Period and Frequency
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Period and Frequency
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Example
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More About Frequency
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More About Frequency
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More About Frequency
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Phase
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Three sine waves with the same amplitude and frequency, but different phases
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Phase
Phase is measured in degrees or radians.
A phase shift of 360° corresponds to a shift of a complete period.
A phase shift of 180° corresponds to a shift of one-half of a period.
A phase shift of 90° corresponds to a shift of one-quarter of a period.
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Example
A sine wave is offset 1/6 cycle with respect to time 0.What is its phase in degrees and radians?
SolutionWe know that 1 complete cycle is 360°. Therefore, 1/6cycle is
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Thank You